On Tue, Jul 14, 2026 at 6:05 PM Konstantinos Eleftheriou <[email protected]> wrote: > > Recognize the longhand wide-multiplication carry idiom and fold it to a > widening multiply followed by a right shift for the high part, and a > plain MULT_EXPR for the low part. > > The carry idiom is the schoolbook expansion of a 2N-bit unsigned > multiply written as a top-level + chain of four NxN partial products > plus one overflow-compare carry: > > xh*yh + (cross_sum >> N) + (low_accum >> N) + ((hilo > cross_sum) << N) > cross_sum = xh*yl + xl*yh > low_accum = (xl*yl >> N) + (cross_sum & mask) > > For example, this AArch64 sequence from SPEC2026's 750.sealcrypto_r: > > lsr x4, x0, 32 > lsr x6, x1, 32 > umull x3, w0, w1 > umull x1, w1, w4 > and x5, x3, 4294967295 > umaddl x0, w0, w6, x1 > cmp x1, x0 > and x1, x0, 4294967295 > lsr x0, x0, 32 > add x3, x1, x3, lsr 32 > cset x1, hi > orr x5, x5, x3, lsl 32 > umaddl x4, w4, w6, x0 > extr x0, x1, x3, 32 > add x0, x0, x4 > stp x5, x0, [x2] > > can be transformed to: > > umulh x3, x1, x0 > mul x0, x0, x1 > stp x0, x3, [x2] > > Atom-level pattern recognition is implemented via match patterns in > match.pd (mul_hi, mul_lo, mul_hilo, mul_lolo, mul_hihi, mul_cross_sum, > mul_low_accum, mul_carry_cross_sum). The composite recognition that > ties atoms into a long-multiplication chain is performed in forwprop > by match_long_mul: it linearizes the outer add/ior chain into a > multiset of summands, classifies each summand via the match.pd atoms, > and looks the multiset up in long_mul_table to identify the variant. > On a hit, three cross-summand consistency checks (one operand pair, > half-width shifts, hilo cross-half products) gate the rewrite. > > The HIGH_PART row emits the canonical widening shape > > (N)(((2N) op1 * (2N) op2) >> N) > > which pass_optimize_widening_mul later lowers to a single > WIDEN_MULT_EXPR or MULT_HIGHPART_EXPR on targets that support it. > The LOW_PART row emits a plain MULT_EXPR. HIGH_PART is emitted only > when the 2N mode is present in the mode table. > > Bootstrapped/regtested on AArch64, x86-64 and PowerPC.
Minor comments in-line, this looks good overall I think. Richard. > PR tree-optimization/107090 > > gcc/ChangeLog: > > * match.pd: Add atom match recognizers for long-multiply > (mul_hi, mul_lo, mul_hilo, mul_lolo, mul_hihi, mul_cross_sum, > mul_low_accum, mul_carry_cross_sum). > * tree-ssa-forwprop.cc (gimple_mul_hi): Declare. > (gimple_mul_lo): Likewise. > (gimple_mul_hilo): Likewise. > (gimple_mul_lolo): Likewise. > (gimple_mul_hihi): Likewise. > (gimple_mul_cross_sum): Likewise. > (gimple_mul_low_accum): Likewise. > (gimple_mul_carry_cross_sum): Likewise. > (create_mul_high_seq): New, emits (N)(((2N) op1 * (2N) op2) >> N). > (create_mul_low_seq): New, emits MULT_EXPR. > (enum long_mul_kind): New. > (enum long_mul_extract): New. > (struct long_mul_summand): New. > (long_mul_linearize_chain): New, walks the outer add/ior chain > into a multiset of leaves. > (long_mul_is_lshift_def): New. > (long_mul_set_summand): New. > (long_mul_classify_carry): New. > (long_mul_classify_plus_kinds): New. > (long_mul_classify_hi_extract): New. > (long_mul_classify_lo_extract): New. > (long_mul_classify_shl_extract): New. > (long_mul_classify_bare): New. > (long_mul_classify_summand): New, classify each summand via the > match.pd atoms. > (long_mul_summand_compare): New. > (struct long_mul_row): New. > (long_mul_same_ops): New. > (long_mul_is_cross_half): New. > (long_mul_hilo_orientation): New, orientation of a mul_hilo > capture relative to (op0, op1). > (long_mul_canonical_ops): New. > (long_mul_check_consistency): New, cross-summand consistency > check (operand pairing, half-width shifts, hilo cross-half). > (long_mul_signature_matches): New. > (long_mul_hint_shared_intermediate): New, dump-file hint > pointing at a shared inner addition. > (match_long_mul): New, top-level entry: linearizes the outer > add/ior chain, classifies summands, looks the multiset up in > long_mul_table, runs cross-summand consistency checks, and > dispatches to create_mul_high_seq / create_mul_low_seq. > (pass_forwprop::execute): Call match_long_mul on PLUS_EXPR and > BIT_IOR_EXPR statements. > > gcc/testsuite/ChangeLog: > > * gcc.dg/tree-ssa/long-mul-carry.c: New test. > * gcc.target/aarch64/long_mul.c: New test. > * gcc.target/i386/long_mul.c: New test. > > Co-authored-by: Philipp Tomsich <[email protected]> > Signed-off-by: Konstantinos Eleftheriou <[email protected]> > --- > > (no changes since v1) > > gcc/match.pd | 73 ++ > .../gcc.dg/tree-ssa/long-mul-carry.c | 181 +++++ > gcc/testsuite/gcc.target/aarch64/long_mul.c | 58 ++ > gcc/testsuite/gcc.target/i386/long_mul.c | 58 ++ > gcc/tree-ssa-forwprop.cc | 701 +++++++++++++++++- > 5 files changed, 1066 insertions(+), 5 deletions(-) > create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/long-mul-carry.c > create mode 100644 gcc/testsuite/gcc.target/aarch64/long_mul.c > create mode 100644 gcc/testsuite/gcc.target/i386/long_mul.c > > diff --git a/gcc/match.pd b/gcc/match.pd > index 9d4ab622fe57..5a4b1923b589 100644 > --- a/gcc/match.pd > +++ b/gcc/match.pd > @@ -12160,6 +12160,79 @@ and, > INTEGER_CST@2) INTEGER_CST@3) > (if (compare_tree_int (@sub1, 1) == 0))) > > +#if GIMPLE > +/* Match low and high parts of longhand multiplication. > + Given a 2N-bit unsigned type, x = xh*2^N + xl and y = yh*2^N + yl, > + where xh, xl, yh, yl are N-bit halves extracted via shifts and masks. */ > + > +/* High half: op >> N. */ > +(match (mul_hi @op @0) > + (rshift @op INTEGER_CST@0) > + (with { > + tree op_type = TREE_TYPE (@op); } > + (if (INTEGRAL_TYPE_P (op_type) > + && TYPE_UNSIGNED (op_type) > + && TYPE_PRECISION (op_type) % 2 == 0 > + && tree_fits_uhwi_p (@0) > + && tree_to_uhwi (@0) == TYPE_PRECISION (op_type) / 2)))) > +/* Low half: op & mask. */ > +(match (mul_lo @op @0) > + (bit_and @op INTEGER_CST@0) > + (with { > + tree op_type = TREE_TYPE (@op); } > + (if (INTEGRAL_TYPE_P (op_type) > + && TYPE_UNSIGNED (op_type) > + && TYPE_PRECISION (op_type) % 2 == 0 > + && tree_fits_uhwi_p (@0) > + && tree_to_uhwi (@0) == wi::mask ( > + TYPE_PRECISION (op_type) / 2, > + false, > + TYPE_PRECISION (op_type)))))) > +/* Cross product: high(op0) * low(op1). */ > +(match (mul_hilo @op0 @op1 @0 @1) > + (mult:c > + (mul_hi @op0 INTEGER_CST@0) > + (mul_lo @op1 INTEGER_CST@1))) > +/* Low-low product: low(op0) * low(op1). */ > +(match (mul_lolo @op0 @op1 @0) > + (mult:c > + (mul_lo @op0 INTEGER_CST@0) > + (mul_lo @op1 INTEGER_CST@0))) > +/* High-high product: high(op0) * high(op1). */ > +(match (mul_hihi @op0 @op1 @0) > + (mult:c > + (mul_hi @op0 INTEGER_CST@0) > + (mul_hi @op1 INTEGER_CST@0))) > +/* Cross sum: xh*yl + xl*yh. > + Note: matches any PLUS; operands are validated as actual cross > + products by the forwprop consumer (long_mul_check_consistency). */ > +(match (mul_cross_sum @mul_hilo0 @mul_hilo1) > + (plus:c @mul_hilo0 @mul_hilo1)) > +/* Carry from cross-sum overflow: (cast?) (hilo > cross_sum) << N. > + Explicit guard required because mul_cross_sum is just (plus:c @0 @1) > + with no inherent type or halfwidth constraint. */ > +(match (mul_carry_cross_sum @mul_hilo0 @mul_hilo1 @mul_hilo2 @0) > + (lshift > + (convert? (gt > + @mul_hilo0 > + (mul_cross_sum @mul_hilo1 @mul_hilo2))) > + INTEGER_CST@0) > + (with { > + tree op_type = TREE_TYPE (@mul_hilo0); } > + (if (INTEGRAL_TYPE_P (op_type) > + && TYPE_UNSIGNED (op_type) > + && TYPE_PRECISION (op_type) % 2 == 0 > + && tree_fits_uhwi_p (@0) > + && tree_to_uhwi (@0) == TYPE_PRECISION (op_type) / 2)))) > +/* Low accumulate: (xl*yl >> N) + (cross_sum & mask). */ > +(match (mul_low_accum @op0 @op1 @mul_hilo0 @mul_hilo1 @0 @1) > + (plus:c > + (mul_hi > + (mul_lolo @op0 @op1 INTEGER_CST@0) > + INTEGER_CST@1) > + (mul_lo (mul_cross_sum @mul_hilo0 @mul_hilo1) INTEGER_CST@0))) > +#endif > + > /* Floatint point/integer comparison and integer->integer > or floating point -> float point conversion. */ > (match (cond_expr_convert_p @0 @2 @3 @6) > diff --git a/gcc/testsuite/gcc.dg/tree-ssa/long-mul-carry.c > b/gcc/testsuite/gcc.dg/tree-ssa/long-mul-carry.c > new file mode 100644 > index 000000000000..bbdbc63ac0bb > --- /dev/null > +++ b/gcc/testsuite/gcc.dg/tree-ssa/long-mul-carry.c > @@ -0,0 +1,181 @@ > +/* { dg-do compile } */ > +/* { dg-options "-O3 -fdump-tree-forwprop-details" } */ > + > +typedef __UINT32_TYPE__ uint32_t; > +typedef __UINT64_TYPE__ uint64_t; > +typedef struct { uint32_t v[2]; } v2i32; > + > +/* High part follows the long form > + xh*yh + carry + (cross_sum >> N) + (low_accum >> N). */ > + > +uint64_t mulh_carry (uint64_t x, uint64_t y) > +{ > + uint64_t x_lo = x & 0xFFFFFFFF; > + uint64_t x_hi = x >> 32; > + uint64_t y_lo = y & 0xFFFFFFFF; > + uint64_t y_hi = y >> 32; > + uint64_t y_lo_x_hi = y_lo * x_hi; > + uint64_t y_hi_x_hi = y_hi * x_hi; > + uint64_t y_hi_x_lo = y_hi * x_lo; > + uint64_t y_lo_x_lo = y_lo * x_lo; > + uint64_t cross_sum = y_hi_x_lo + y_lo_x_hi; > + int carry_out = cross_sum < y_lo_x_hi; > + uint64_t carry = (uint64_t) carry_out << 32; > + uint64_t y_lo_x_lo_hi = y_lo_x_lo >> 32; > + uint64_t cross_sum_lo = cross_sum & 0xFFFFFFFF; > + uint64_t cross_sum_hi = cross_sum >> 32; > + uint64_t low_accum = cross_sum_lo + y_lo_x_lo_hi; > + uint64_t interm = cross_sum_hi + y_hi_x_hi; > + uint64_t low_accum_hi = low_accum >> 32; > + uint64_t interm_plus_carry = interm + carry; > + uint64_t hw64 = interm_plus_carry + low_accum_hi; > + > + return hw64; > +} > + > +uint64_t mulh_carry_comm (uint64_t x, uint64_t y) > +{ > + uint64_t x_lo = x & 0xFFFFFFFF; > + uint64_t y_lo = y & 0xFFFFFFFF; > + uint64_t x_hi = x >> 32; > + uint64_t y_hi = y >> 32; > + uint64_t y_lo_x_hi = x_hi * y_lo; > + uint64_t y_hi_x_hi = y_hi * x_hi; > + uint64_t y_hi_x_lo = x_lo * y_hi; > + uint64_t y_lo_x_lo = x_lo * y_lo; > + uint64_t cross_sum = y_lo_x_hi + y_hi_x_lo; > + int carry_out = (cross_sum < y_lo_x_hi); > + uint64_t carry = (uint64_t) carry_out << 32; > + uint64_t y_lo_x_lo_hi = y_lo_x_lo >> 32; > + uint64_t cross_sum_lo = cross_sum & 0xFFFFFFFF; > + uint64_t cross_sum_hi = cross_sum >> 32; > + uint64_t low_accum = y_lo_x_lo_hi + cross_sum_lo; > + uint64_t inter = y_hi_x_hi + cross_sum_hi; > + uint64_t low_accum_hi = low_accum >> 32; > + uint64_t interm_plus_carry = carry + inter; > + uint64_t hw64 = low_accum_hi + interm_plus_carry; > + > + return hw64; > +} > + > +uint32_t mulh_carry_32 (uint32_t x, uint32_t y) > +{ > + uint32_t x_lo = x & 0xFFFF; > + uint32_t x_hi = x >> 16; > + uint32_t y_lo = y & 0xFFFF; > + uint32_t y_hi = y >> 16; > + uint32_t y_lo_x_hi = y_lo * x_hi; > + uint32_t y_hi_x_hi = y_hi * x_hi; > + uint32_t y_hi_x_lo = y_hi * x_lo; > + uint32_t y_lo_x_lo = y_lo * x_lo; > + uint32_t cross_sum = y_hi_x_lo + y_lo_x_hi; > + int carry_out = (cross_sum < y_lo_x_hi); > + uint32_t carry = (uint32_t) carry_out << 16; > + uint32_t y_lo_x_lo_hi = y_lo_x_lo >> 16; > + uint32_t cross_sum_lo = cross_sum & 0xFFFF; > + uint32_t cross_sum_hi = cross_sum >> 16; > + uint32_t low_accum = cross_sum_lo + y_lo_x_lo_hi; > + uint32_t interm = cross_sum_hi + y_hi_x_hi; > + uint32_t low_accum_hi = low_accum >> 16; > + uint32_t interm_plus_carry = interm + carry; > + uint32_t hw64 = interm_plus_carry + low_accum_hi; > + > + return hw64; > +} > + > +/* The 128-bit variant lowers to longhand in pass_optimize_widening_mul; > + no target provides a 256-bit multiply. */ > +#ifdef __SIZEOF_INT128__ > +__uint128_t mulh_carry_128 (__uint128_t x, __uint128_t y) > +{ > + __uint128_t x_lo = x & (__uint128_t)0xFFFFFFFFFFFFFFFF; > + __uint128_t x_hi = x >> 64; > + __uint128_t y_lo = y & (__uint128_t)0xFFFFFFFFFFFFFFFF; > + __uint128_t y_hi = y >> 64; > + __uint128_t y_lo_x_hi = y_lo * x_hi; > + __uint128_t y_hi_x_hi = y_hi * x_hi; > + __uint128_t y_hi_x_lo = y_hi * x_lo; > + __uint128_t y_lo_x_lo = y_lo * x_lo; > + __uint128_t cross_sum = y_hi_x_lo + y_lo_x_hi; > + int carry_out = cross_sum < y_lo_x_hi; > + __uint128_t carry = (__uint128_t) carry_out << 64; > + __uint128_t y_lo_x_lo_hi = y_lo_x_lo >> 64; > + __uint128_t cross_sum_lo = cross_sum & (__uint128_t)0xFFFFFFFFFFFFFFFF; > + __uint128_t cross_sum_hi = cross_sum >> 64; > + __uint128_t low_accum = cross_sum_lo + y_lo_x_lo_hi; > + __uint128_t interm = cross_sum_hi + y_hi_x_hi; > + __uint128_t low_accum_hi = low_accum >> 64; > + __uint128_t interm_plus_carry = interm + carry; > + __uint128_t hw64 = interm_plus_carry + low_accum_hi; > + > + return hw64; > +} > +#endif > + > +void full_mul_carry (uint64_t x, uint64_t y, uint64_t* p) { > + uint64_t x_lo = x & 0xFFFFFFFF; > + uint64_t y_lo = y & 0xFFFFFFFF; > + uint64_t x_hi = x >> 32; > + uint64_t y_hi = y >> 32; > + uint64_t y_lo_x_hi = y_lo * x_hi; > + uint64_t y_hi_x_hi = y_hi * x_hi; > + uint64_t y_hi_x_lo = y_hi * x_lo; > + uint64_t y_lo_x_lo = y_lo * x_lo; > + uint64_t cross_sum = y_hi_x_lo + y_lo_x_hi; > + int carry_out = (cross_sum < y_lo_x_hi); > + uint64_t carry = (uint64_t) carry_out << 32; > + uint64_t y_lo_x_lo_hi = y_lo_x_lo >> 32; > + uint64_t cross_sum_lo = cross_sum & 0xFFFFFFFF; > + uint64_t cross_sum_hi = cross_sum >> 32; > + uint64_t low_accum = cross_sum_lo + y_lo_x_lo_hi; > + uint64_t upper_mid = y_hi_x_hi + carry; > + uint64_t low_accum_hi = low_accum >> 32; > + uint64_t upper_mid_with_cross = upper_mid + cross_sum_hi; > + uint64_t hw64 = upper_mid_with_cross + low_accum_hi; > + p[1] = hw64; > + uint64_t low_accum_shifted = low_accum << 32; > + uint64_t y_lo_x_lo_lo = y_lo_x_lo & 0xFFFFFFFF; > + uint64_t lw64 = low_accum_shifted | y_lo_x_lo_lo; > + p[0] = lw64; > +} > + > +/* This will be optimized during the second forwprop run. > + Disable SLP so the expected fold count is target-independent. */ > +__attribute__((optimize("no-tree-slp-vectorize"))) > +v2i32 mulh_carry_v2i32 (v2i32 x, v2i32 y) > +{ > + v2i32 result; > + for (int i = 0; i < 2; i++) > + { > + uint32_t x_lo = x.v[i] & 0xFFFF; > + uint32_t y_lo = y.v[i] & 0xFFFF; > + uint32_t x_hi = x.v[i] >> 16; > + uint32_t y_hi = y.v[i] >> 16; > + > + uint32_t y_lo_x_hi = y_lo * x_hi; > + uint32_t y_hi_x_hi = y_hi * x_hi; > + uint32_t y_hi_x_lo = y_hi * x_lo; > + uint32_t y_lo_x_lo = y_lo * x_lo; > + > + uint32_t cross_sum = y_hi_x_lo + y_lo_x_hi; > + int carry_out = cross_sum < y_lo_x_hi; > + uint32_t carry = (uint32_t) carry_out << 16; > + > + uint32_t y_lo_x_lo_hi = y_lo_x_lo >> 16; > + uint32_t cross_sum_lo = cross_sum & 0xFFFF; > + uint32_t cross_sum_hi = cross_sum >> 16; > + > + uint32_t low_accum = cross_sum_lo + y_lo_x_lo_hi; > + uint32_t interm = cross_sum_hi + y_hi_x_hi; > + uint32_t low_accum_hi = low_accum >> 16; > + uint32_t interm_plus_carry = interm + carry; > + > + result.v[i] = interm_plus_carry + low_accum_hi; > + } > + > + return result; > +} > + > +/* { dg-final { scan-tree-dump-times "Long multiplication high part folded." > 4 "forwprop1" } } */ > +/* { dg-final { scan-tree-dump-times "Long multiplication high part folded." > 1 "forwprop2" } } */ > +/* { dg-final { scan-tree-dump-times "Long multiplication low part folded." > 1 "forwprop1" } } */ > diff --git a/gcc/testsuite/gcc.target/aarch64/long_mul.c > b/gcc/testsuite/gcc.target/aarch64/long_mul.c > new file mode 100644 > index 000000000000..2a4709ecbfd0 > --- /dev/null > +++ b/gcc/testsuite/gcc.target/aarch64/long_mul.c > @@ -0,0 +1,58 @@ > +/* { dg-do compile } */ > +/* { dg-options "-O3" } */ > + > +typedef __UINT32_TYPE__ uint32_t; > +typedef __UINT64_TYPE__ uint64_t; > + > +/* 64-bit carry pattern for high part. */ > +uint64_t mulh_carry (uint64_t x, uint64_t y) > +{ > + uint64_t x_lo = x & 0xFFFFFFFF; > + uint64_t x_hi = x >> 32; > + uint64_t y_lo = y & 0xFFFFFFFF; > + uint64_t y_hi = y >> 32; > + uint64_t y_lo_x_hi = y_lo * x_hi; > + uint64_t y_hi_x_hi = y_hi * x_hi; > + uint64_t y_hi_x_lo = y_hi * x_lo; > + uint64_t y_lo_x_lo = y_lo * x_lo; > + uint64_t cross_sum = y_hi_x_lo + y_lo_x_hi; > + int carry_out = cross_sum < y_lo_x_hi; > + uint64_t carry = (uint64_t) carry_out << 32; > + uint64_t y_lo_x_lo_hi = y_lo_x_lo >> 32; > + uint64_t cross_sum_lo = cross_sum & 0xFFFFFFFF; > + uint64_t cross_sum_hi = cross_sum >> 32; > + uint64_t low_accum = cross_sum_lo + y_lo_x_lo_hi; > + uint64_t interm = cross_sum_hi + y_hi_x_hi; > + uint64_t low_accum_hi = low_accum >> 32; > + uint64_t interm_plus_carry = interm + carry; > + return interm_plus_carry + low_accum_hi; > +} > + > +/* 32-bit carry pattern for high part. */ > +uint32_t mulh_carry_32 (uint32_t x, uint32_t y) > +{ > + uint32_t x_lo = x & 0xFFFF; > + uint32_t x_hi = x >> 16; > + uint32_t y_lo = y & 0xFFFF; > + uint32_t y_hi = y >> 16; > + uint32_t y_lo_x_hi = y_lo * x_hi; > + uint32_t y_hi_x_hi = y_hi * x_hi; > + uint32_t y_hi_x_lo = y_hi * x_lo; > + uint32_t y_lo_x_lo = y_lo * x_lo; > + uint32_t cross_sum = y_hi_x_lo + y_lo_x_hi; > + int carry_out = (cross_sum < y_lo_x_hi); > + uint32_t carry = (uint32_t) carry_out << 16; > + uint32_t y_lo_x_lo_hi = y_lo_x_lo >> 16; > + uint32_t cross_sum_lo = cross_sum & 0xFFFF; > + uint32_t cross_sum_hi = cross_sum >> 16; > + uint32_t low_accum = cross_sum_lo + y_lo_x_lo_hi; > + uint32_t interm = cross_sum_hi + y_hi_x_hi; > + uint32_t low_accum_hi = low_accum >> 16; > + uint32_t interm_plus_carry = interm + carry; > + return interm_plus_carry + low_accum_hi; > +} > + > +/* 64-bit pattern should emit umulh. */ > +/* { dg-final { scan-assembler-times "umulh\t" 1 } } */ > +/* 32-bit pattern should emit umull (32x32->64 widening multiply). */ > +/* { dg-final { scan-assembler-times "umull\t" 1 } } */ > diff --git a/gcc/testsuite/gcc.target/i386/long_mul.c > b/gcc/testsuite/gcc.target/i386/long_mul.c > new file mode 100644 > index 000000000000..6ec87eb8dd21 > --- /dev/null > +++ b/gcc/testsuite/gcc.target/i386/long_mul.c > @@ -0,0 +1,58 @@ > +/* { dg-do compile { target { ! ia32 } } } */ > +/* { dg-options "-O3" } */ > + > +typedef __UINT32_TYPE__ uint32_t; > +typedef __UINT64_TYPE__ uint64_t; > + > +/* 64-bit carry pattern for high part. */ > +uint64_t mulh_carry (uint64_t x, uint64_t y) > +{ > + uint64_t x_lo = x & 0xFFFFFFFF; > + uint64_t x_hi = x >> 32; > + uint64_t y_lo = y & 0xFFFFFFFF; > + uint64_t y_hi = y >> 32; > + uint64_t y_lo_x_hi = y_lo * x_hi; > + uint64_t y_hi_x_hi = y_hi * x_hi; > + uint64_t y_hi_x_lo = y_hi * x_lo; > + uint64_t y_lo_x_lo = y_lo * x_lo; > + uint64_t cross_sum = y_hi_x_lo + y_lo_x_hi; > + int carry_out = cross_sum < y_lo_x_hi; > + uint64_t carry = (uint64_t) carry_out << 32; > + uint64_t y_lo_x_lo_hi = y_lo_x_lo >> 32; > + uint64_t cross_sum_lo = cross_sum & 0xFFFFFFFF; > + uint64_t cross_sum_hi = cross_sum >> 32; > + uint64_t low_accum = cross_sum_lo + y_lo_x_lo_hi; > + uint64_t interm = cross_sum_hi + y_hi_x_hi; > + uint64_t low_accum_hi = low_accum >> 32; > + uint64_t interm_plus_carry = interm + carry; > + return interm_plus_carry + low_accum_hi; > +} > + > +/* 32-bit carry pattern for high part. */ > +uint32_t mulh_carry_32 (uint32_t x, uint32_t y) > +{ > + uint32_t x_lo = x & 0xFFFF; > + uint32_t x_hi = x >> 16; > + uint32_t y_lo = y & 0xFFFF; > + uint32_t y_hi = y >> 16; > + uint32_t y_lo_x_hi = y_lo * x_hi; > + uint32_t y_hi_x_hi = y_hi * x_hi; > + uint32_t y_hi_x_lo = y_hi * x_lo; > + uint32_t y_lo_x_lo = y_lo * x_lo; > + uint32_t cross_sum = y_hi_x_lo + y_lo_x_hi; > + int carry_out = (cross_sum < y_lo_x_hi); > + uint32_t carry = (uint32_t) carry_out << 16; > + uint32_t y_lo_x_lo_hi = y_lo_x_lo >> 16; > + uint32_t cross_sum_lo = cross_sum & 0xFFFF; > + uint32_t cross_sum_hi = cross_sum >> 16; > + uint32_t low_accum = cross_sum_lo + y_lo_x_lo_hi; > + uint32_t interm = cross_sum_hi + y_hi_x_hi; > + uint32_t low_accum_hi = low_accum >> 16; > + uint32_t interm_plus_carry = interm + carry; > + return interm_plus_carry + low_accum_hi; > +} > + > +/* 64-bit pattern should emit mulq (unsigned 64x64->128 multiply). */ > +/* { dg-final { scan-assembler-times "\tmulq" 1 } } */ > +/* 32-bit pattern should emit imulq (64-bit multiply of zero-extended > operands). */ > +/* { dg-final { scan-assembler-times "\timulq" 1 } } */ > diff --git a/gcc/tree-ssa-forwprop.cc b/gcc/tree-ssa-forwprop.cc > index 12c07c99c9bd..3870bf17c0e0 100644 > --- a/gcc/tree-ssa-forwprop.cc > +++ b/gcc/tree-ssa-forwprop.cc > @@ -3592,6 +3592,693 @@ simplify_count_zeroes (gimple_stmt_iterator *gsi) > return true; > } > > +/* Match.pd functions to match long multiplication. */ > + > +extern bool gimple_mul_hi (tree, tree *, tree (*)(tree)); > +extern bool gimple_mul_lo (tree, tree *, tree (*)(tree)); > +extern bool gimple_mul_hilo (tree, tree *, tree (*)(tree)); > +extern bool gimple_mul_lolo (tree, tree *, tree (*)(tree)); > +extern bool gimple_mul_hihi (tree, tree *, tree (*)(tree)); > +extern bool gimple_mul_cross_sum (tree, tree *, tree (*)(tree)); > +extern bool gimple_mul_low_accum (tree, tree *, tree (*)(tree)); > +extern bool gimple_mul_carry_cross_sum (tree, tree *, tree (*)(tree)); > + > +/* Replace STMT with a high-part multiply of OP1 and OP2, emitted as > + (N)(((2N) op1 * (2N) op2) >> N). > + pass_optimize_widening_mul's convert_mult_to_widen and > + convert_mult_to_highpart later rewrite this to a single > + WIDEN_MULT_EXPR or MULT_HIGHPART_EXPR when the target supports it, > + otherwise the 2N multiply expands directly. Emitting the canonical > + widening shape keeps target-capability decisions in the layer that > + already owns them. */ > + > +static void > +create_mul_high_seq (tree op1, tree op2, gimple *stmt) > +{ > + tree op_type = TREE_TYPE (op1); > + unsigned int width = TYPE_PRECISION (op_type); > + tree wide_type = build_nonstandard_integer_type (width * 2, 1); > + > + location_t loc = gimple_location (stmt); > + gimple_seq seq = NULL; > + > + tree wide_a = gimple_convert (&seq, loc, wide_type, op1); > + tree wide_b = gimple_convert (&seq, loc, wide_type, op2); > + tree wide_prod = gimple_build (&seq, loc, MULT_EXPR, wide_type, > + wide_a, wide_b); > + tree hi = gimple_build (&seq, loc, RSHIFT_EXPR, wide_type, wide_prod, > + build_int_cst (integer_type_node, width)); > + > + gimple *prod = gimple_build_assign (gimple_get_lhs (stmt), NOP_EXPR, hi); > + gimple_set_location (prod, loc); > + gimple_seq_add_stmt (&seq, prod); > + > + gimple_stmt_iterator gsi = gsi_for_stmt (stmt); > + gsi_replace_with_seq (&gsi, seq, true); > +} > + > +/* Replace STMT with a low-part multiply of OP1 and OP2. */ > + > +static void > +create_mul_low_seq (tree op1, tree op2, gimple *stmt) > +{ > + gimple *prod = gimple_build_assign (gimple_get_lhs (stmt), > + MULT_EXPR, op1, op2); > + gimple_set_location (prod, gimple_location (stmt)); > + gimple_stmt_iterator gsi = gsi_for_stmt (stmt); > + gsi_replace (&gsi, prod, true); > +} > + > +/* Long-multiply fold framework. > + > + Walks the outer addition or bit_ior chain on a candidate statement, > + classifies each summand against the atom match patterns from > + match.pd, and looks the resulting multiset of (kind, extract) tuples > + up in a table. On a hit, three cross-summand consistency checks > + decide whether the wide multiply is emitted. */ > + > +/* Widest match.pd atom (mul_low_accum) takes 6 captures; round up > + to 8 for the scratch buffers below. */ > +static constexpr unsigned LONG_MUL_MAX_CAPTURES = 8; > + > +/* Longest variant in long_mul_table has 4 summands. */ > +static constexpr unsigned LONG_MUL_MAX_SUMMANDS = 4; > + > +enum long_mul_kind { > + LMK_MUL_HIHI, > + LMK_MUL_LOLO, > + LMK_MUL_HILO, > + LMK_CROSS_SUM, > + LMK_LOW_ACCUM, > + LMK_CARRY_CROSS_SUM, > +}; > + > +/* How the leaf wraps its inner kind. Carry kinds use LMX_NONE: their > + match.pd pattern bakes the lshift in, so the leaf is already the > + complete carry expression. */ > + > +enum long_mul_extract { > + LMX_NONE, > + LMX_HI, > + LMX_LO, > + LMX_SHL_N, > +}; > + > +struct long_mul_summand { > + long_mul_kind kind; > + long_mul_extract extract; > + tree op0, op1; > + tree hilo0, hilo1, hilo2; > + unsigned HOST_WIDE_INT shift; > + unsigned HOST_WIDE_INT mask; > +}; > + > +/* Walk the OUTER addition or BIT_IOR chain rooted at STMT and collect > + the leaf operands into LEAVES. Descends through single-use > + intermediate stmts of the same code. Returns false once the leaf > + count exceeds LONG_MUL_MAX_SUMMANDS, so an overlong chain bails > + mid-walk instead of after a full traversal. > + > + If SHARED_DEF_OUT is non-NULL, record there the first inner stmt that > + shares the outer code but has more than one use -- descending into it > + would change semantics, so it stays as a leaf. Such a leaf often > + classifies as something no row matches, silently disabling the fold; > + the caller surfaces this as a dump-file hint. */ > + > +static bool > +long_mul_linearize_chain (gimple *stmt, tree_code outer, vec<tree> &leaves, > + gimple **shared_def_out = NULL) > +{ > + auto_vec<tree, 8> stack; > + stack.safe_push (gimple_assign_rhs2 (stmt)); > + stack.safe_push (gimple_assign_rhs1 (stmt)); > + > + while (!stack.is_empty ()) > + { > + tree t = stack.pop (); > + if (TREE_CODE (t) == SSA_NAME) > + { > + gimple *def = SSA_NAME_DEF_STMT (t); > + if (def > + && is_gimple_assign (def) > + && gimple_assign_rhs_code (def) == outer) > + { > + if (has_single_use (t)) > + { > + stack.safe_push (gimple_assign_rhs2 (def)); > + stack.safe_push (gimple_assign_rhs1 (def)); > + continue; > + } > + if (shared_def_out && !*shared_def_out) > + *shared_def_out = def; > + } > + } > + leaves.safe_push (t); > + if (leaves.length () > LONG_MUL_MAX_SUMMANDS) > + return false; > + } > + return !leaves.is_empty (); > +} > + > +/* If EXPR is defined by LSHIFT_EXPR with a uhwi-valued amount, return > + the shifted input via *INNER_OUT and the amount via *SHIFT_OUT. */ > + > +static bool > +long_mul_is_lshift_def (tree expr, tree *inner_out, > + unsigned HOST_WIDE_INT *shift_out) > +{ > + if (TREE_CODE (expr) != SSA_NAME) > + return false; > + gimple *def = SSA_NAME_DEF_STMT (expr); > + if (!def || !is_gimple_assign (def) > + || gimple_assign_rhs_code (def) != LSHIFT_EXPR) > + return false; > + tree amount = gimple_assign_rhs2 (def); > + if (!tree_fits_uhwi_p (amount)) > + return false; > + *inner_out = gimple_assign_rhs1 (def); > + *shift_out = tree_to_uhwi (amount); > + return true; > +} > + > +/* Fill INFO's kind plus the captures from RES_OPS that the kind requires. > + The kind itself determines how many (op0, op1) and hilo captures to > + pick up from RES_OPS, and whether a baked-in shift is present. */ > + > +static void > +long_mul_set_summand (long_mul_summand *info, long_mul_kind kind, > + const tree *res_ops) > +{ > + info->kind = kind; > + unsigned n_ops = 0; > + unsigned n_hilos = 0; > + int shift_idx = -1; > + switch (kind) > + { > + case LMK_MUL_HIHI: > + case LMK_MUL_LOLO: > + case LMK_MUL_HILO: > + n_ops = 2; > + break; > + case LMK_CROSS_SUM: > + n_hilos = 2; > + break; > + case LMK_LOW_ACCUM: > + n_ops = 2; > + n_hilos = 2; > + break; > + case LMK_CARRY_CROSS_SUM: > + n_hilos = 3; > + shift_idx = 3; > + break; > + } > + if (n_ops >= 1) > + info->op0 = res_ops[0]; > + if (n_ops >= 2) > + info->op1 = res_ops[1]; > + if (n_hilos >= 1) > + info->hilo0 = res_ops[n_ops]; > + if (n_hilos >= 2) > + info->hilo1 = res_ops[n_ops + 1]; > + if (n_hilos >= 3) > + info->hilo2 = res_ops[n_ops + 2]; > + if (shift_idx >= 0) > + info->shift = tree_to_uhwi (res_ops[shift_idx]); is this verified to tree_fits_uhwi_p somewhere? > +} > + > +/* Classify LEAF as a carry-kind summand. The lshift amount is baked > + into mul_carry_cross_sum, so it's tried before any branch that looks > + for a generic (X >> N) or (X << N) wrapper. */ > + > +static bool > +long_mul_classify_carry (tree leaf, long_mul_summand *info) > +{ > + tree res_ops[LONG_MUL_MAX_CAPTURES]; > + if (gimple_mul_carry_cross_sum (leaf, res_ops, NULL)) > + { > + long_mul_set_summand (info, LMK_CARRY_CROSS_SUM, res_ops); > + return true; > + } > + return false; > +} > + > +/* Plus-based summand kinds shared by the (X >> SHIFT) and (X << SHIFT) > + classifiers. */ > + > +static bool > +long_mul_classify_plus_kinds (tree inner, long_mul_summand *info) > +{ > + tree res_ops[LONG_MUL_MAX_CAPTURES]; > + if (gimple_mul_low_accum (inner, res_ops, NULL)) > + { > + long_mul_set_summand (info, LMK_LOW_ACCUM, res_ops); > + return true; > + } > + return false; > +} > + > +/* Classify INNER -- already unwrapped from an outer (X >> SHIFT) -- as > + a high-half-extracted summand. mul_hilo (mult-shape) is orthogonal > + to the plus-based kinds and is tried first; mul_cross_sum (any plus) > + is the fallback after the shared plus-based kinds. */ > + > +static bool > +long_mul_classify_hi_extract (tree inner, unsigned HOST_WIDE_INT shift, > + long_mul_summand *info) > +{ > + tree res_ops[LONG_MUL_MAX_CAPTURES]; > + info->extract = LMX_HI; > + info->shift = shift; > + if (gimple_mul_hilo (inner, res_ops, NULL)) > + { > + long_mul_set_summand (info, LMK_MUL_HILO, res_ops); > + return true; > + } > + if (long_mul_classify_plus_kinds (inner, info)) > + return true; > + if (gimple_mul_cross_sum (inner, res_ops, NULL)) > + { > + long_mul_set_summand (info, LMK_CROSS_SUM, res_ops); > + return true; > + } > + return false; > +} > + > +/* Classify INNER -- already unwrapped from an outer (X & MASK) -- as > + a low-half-masked summand. */ > + > +static bool > +long_mul_classify_lo_extract (tree inner, unsigned HOST_WIDE_INT mask, > + long_mul_summand *info) > +{ > + tree res_ops[LONG_MUL_MAX_CAPTURES]; > + info->extract = LMX_LO; > + info->mask = mask; > + if (gimple_mul_lolo (inner, res_ops, NULL)) > + { > + long_mul_set_summand (info, LMK_MUL_LOLO, res_ops); > + return true; > + } > + return false; > +} > + > +/* Classify INNER -- already unwrapped from an outer (X << SHIFT) -- as > + a left-shifted summand. No mul_hilo here -- that shape appears only > + under (X >> SHIFT). */ > + > +static bool > +long_mul_classify_shl_extract (tree inner, unsigned HOST_WIDE_INT shift, > + long_mul_summand *info) > +{ > + tree res_ops[LONG_MUL_MAX_CAPTURES]; > + info->extract = LMX_SHL_N; > + info->shift = shift; > + if (long_mul_classify_plus_kinds (inner, info)) > + return true; > + if (gimple_mul_cross_sum (inner, res_ops, NULL)) > + { > + long_mul_set_summand (info, LMK_CROSS_SUM, res_ops); > + return true; > + } > + return false; > +} > + > +/* Classify LEAF as one of the bare-kind summands (no extraction > + wrapper): mul_hihi or mul_lolo standing on their own. */ > + > +static bool > +long_mul_classify_bare (tree leaf, long_mul_summand *info) > +{ > + tree res_ops[LONG_MUL_MAX_CAPTURES]; > + if (gimple_mul_hihi (leaf, res_ops, NULL)) > + { > + long_mul_set_summand (info, LMK_MUL_HIHI, res_ops); > + return true; > + } > + if (gimple_mul_lolo (leaf, res_ops, NULL)) > + { > + long_mul_set_summand (info, LMK_MUL_LOLO, res_ops); > + return true; > + } > + return false; > +} > + > +/* Classify LEAF as one of the long-multiply summand shapes. On success, > + fill *INFO with the kind, extract, captured operands and shift/mask. > + Dispatches to per-extract helpers; the order matters because the > + carry kinds bake an lshift into the pattern and would otherwise be > + misread by the (X << N) branch. */ > + > +static bool > +long_mul_classify_summand (tree leaf, long_mul_summand *info) > +{ > + tree res_ops[LONG_MUL_MAX_CAPTURES]; > + *info = {}; > + > + if (long_mul_classify_carry (leaf, info)) > + return true; > + > + if (gimple_mul_hi (leaf, res_ops, NULL)) > + return long_mul_classify_hi_extract (res_ops[0], > + tree_to_uhwi (res_ops[1]), info); > + > + if (gimple_mul_lo (leaf, res_ops, NULL)) > + return long_mul_classify_lo_extract (res_ops[0], > + tree_to_uhwi (res_ops[1]), info); > + > + tree inner; > + unsigned HOST_WIDE_INT shift; > + if (long_mul_is_lshift_def (leaf, &inner, &shift)) > + return long_mul_classify_shl_extract (inner, shift, info); > + > + return long_mul_classify_bare (leaf, info); > +} > + > +/* qsort comparator: sort summands by (kind, extract) to put a multiset > + into canonical order for table lookup. Unstable sort within a tie is > + harmless: no row in long_mul_table pairs distinct subterms under the > + same (kind, extract), and long_mul_check_consistency cross-validates > + that matching summands share one canonical (op0, op1). */ > + > +static int > +long_mul_summand_compare (const void *a, const void *b) > +{ > + const long_mul_summand *sa = (const long_mul_summand *) a; > + const long_mul_summand *sb = (const long_mul_summand *) b; > + if (sa->kind != sb->kind) > + return (int) sa->kind - (int) sb->kind; > + return (int) sa->extract - (int) sb->extract; > +} > + > +/* One row of the long-multiply variant table. COUNT is how many entries > + of SIG carry the row's signature (2 to LONG_MUL_MAX_SUMMANDS); a row > + with fewer summands leaves the remaining SIG entries zero-initialized. > + Those zeros are not a terminator -- {LMK_MUL_HIHI, LMX_NONE} is itself a > + valid signature -- so long_mul_signature_matches is bounded by COUNT, > + never by a sentinel entry. */ > + > +struct long_mul_row { > + enum long_mul_row_part { HIGH_PART, LOW_PART } part; > + tree_code outer; > + unsigned char count; > + struct { > + long_mul_kind kind; > + long_mul_extract extract; > + } sig[LONG_MUL_MAX_SUMMANDS]; > + bool (*extra_check) (const vec<long_mul_summand> &, gimple *); > +}; > + > +/* True if (A, B) is the same pair as (OP0, OP1) in either order. */ > + > +static inline bool > +long_mul_same_ops (tree a, tree b, tree op0, tree op1) > +{ > + return (a == op0 && b == op1) || (a == op1 && b == op0); > +} > + > +/* True if H is a cross-half product of (OP0, OP1) -- gimple_mul_hilo > + recognizes it and its captured operands match the pair. */ > + > +static bool > +long_mul_is_cross_half (tree h, tree op0, tree op1) > +{ > + tree scratch[LONG_MUL_MAX_CAPTURES]; > + return gimple_mul_hilo (h, scratch, NULL) > + && long_mul_same_ops (scratch[0], scratch[1], op0, op1); > +} > + > +/* Orientation of the mul_hilo capture H relative to (OP0, OP1): > + returns 0 for high(OP0)*low(OP1), 1 for high(OP1)*low(OP0), or -1 > + if H does not decompose that way. A cross-sum of two mul_hilos must > + see one of each orientation -- otherwise a doubled factor would fold > + to the wrong value. (In a self-multiply the two orientations > + coincide; see the OP0 == OP1 bypass in long_mul_check_consistency.) */ > + > +static int > +long_mul_hilo_orientation (tree h, tree op0, tree op1) > +{ > + tree scratch[LONG_MUL_MAX_CAPTURES]; > + if (!gimple_mul_hilo (h, scratch, NULL)) > + return -1; > + if (scratch[0] == op0 && scratch[1] == op1) > + return 0; > + if (scratch[0] == op1 && scratch[1] == op0) > + return 1; > + return -1; > +} > + > +/* Find the first summand that carries operand captures, and return its > + (op0, op1) pair in *OP0_OUT / *OP1_OUT. Returns false if no summand > + provides them. */ > + > +static bool > +long_mul_canonical_ops (const vec<long_mul_summand> &summands, > + tree *op0_out, tree *op1_out) > +{ > + for (const long_mul_summand &s : summands) > + if (s.op0) > + { > + *op0_out = s.op0; > + *op1_out = s.op1; > + return true; > + } > + return false; > +} > + > +/* Run the cross-summand validation invariants and return the canonical > + (op0, op1). Returns false unless all summands that carry operands use > + the same (op0, op1) pair (in either order), every LMX_HI/LMX_SHL_N shift > + equals halfwidth, every captured hilo is a true cross-half product of > + (op0, op1), and every cross-half pair (both those inside a single > + mul_cross_sum-bearing summand and those spread across separate > + LMK_MUL_HILO summands) contains one of each orientation. */ > + > +static bool > +long_mul_check_consistency (const vec<long_mul_summand> &summands, > + tree *op0_out, tree *op1_out) > +{ > + tree op0, op1; > + if (!long_mul_canonical_ops (summands, &op0, &op1)) > + return false; > + > + tree op_type = TREE_TYPE (op0); > + if (!INTEGRAL_TYPE_P (op_type) > + || TYPE_PRECISION (op_type) % 2 != 0) > + return false; > + unsigned int halfwidth = TYPE_PRECISION (op_type) / 2; > + > + /* Self-multiply (x*x) collapses the two cross-halves onto one value, > + so the complementarity constraint is a trivial no-op there. */ > + bool need_orient = op0 != op1; > + int mul_hilo_orient[2] = { 0, 0 }; > + > + for (const long_mul_summand &s : summands) > + { > + if (s.op0 && !long_mul_same_ops (s.op0, s.op1, op0, op1)) > + return false; > + if ((s.extract == LMX_HI || s.extract == LMX_SHL_N) > + && s.shift != halfwidth) > + return false; > + tree hilos[3] = { s.hilo0, s.hilo1, s.hilo2 }; > + for (tree h : hilos) > + if (h && !long_mul_is_cross_half (h, op0, op1)) > + return false; > + > + if (!need_orient) > + continue; > + > + /* The two cross-sum operands are the last two non-null hilos: > + (hilo1, hilo2) for the CARRY_*_SUM kinds, (hilo0, hilo1) for > + the CROSS_SUM / SUM / ACCUM / LADDER_SUM kinds, none for the > + rest. */ > + tree a = NULL_TREE; > + tree b = NULL_TREE; > + if (s.hilo2) > + { > + a = s.hilo1; > + b = s.hilo2; > + } > + else if (s.hilo1) > + { > + a = s.hilo0; > + b = s.hilo1; > + } > + if (a && b > + && (long_mul_hilo_orientation (a, op0, op1) > + == long_mul_hilo_orientation (b, op0, op1))) > + return false; > + > + /* Two LMK_MUL_HILO summands (the two-hilos ladder form) stand for > + the two cross-halves separately; count orientations and require > + the pair to be complementary. s.op0/op1 is already validated to > + match (op0, op1) in some order above. */ > + if (s.kind == LMK_MUL_HILO && s.op0) > + mul_hilo_orient[s.op0 == op1]++; > + } > + > + if (mul_hilo_orient[0] + mul_hilo_orient[1] >= 2 > + && (mul_hilo_orient[0] == 0 || mul_hilo_orient[1] == 0)) > + return false; > + > + *op0_out = op0; > + *op1_out = op1; > + return true; > +} > + > +/* Compare the (already-sorted) SUMMANDS multiset against ROW.sig. */ > + > +static bool > +long_mul_signature_matches (const vec<long_mul_summand> &summands, > + const long_mul_row &row) > +{ > + if (row.count != summands.length ()) > + return false; > + for (unsigned i = 0; i < row.count; i++) > + if (summands[i].kind != row.sig[i].kind > + || summands[i].extract != row.sig[i].extract) > + return false; > + return true; > +} > + > +/* Long-multiply variant table. Each row enumerates the multiset of > + (kind, extract) summands that compose one long-multiply form. Rows > + are sorted by long_mul_summand_compare, matching the input summands' > + sort order, so a plain element-wise compare suffices. Rows describe > + unsigned schoolbook expansions on an even-width 2N-bit type split at > + half-width N; EXTRA_CHECK carries invariants the (kind, extract) > + signature cannot express. */ > + > +static const long_mul_row long_mul_table[] = { > + /* HIGH-PART fold. Notation: xh, xl, yh, yl are the half-width pieces > + of x and y; N is the half-width. cross_sum = xh*yl + xl*yh; hilo is > + either xh*yl or xl*yh (consumers validate the operand shape). */ > + /* xh*yh + (low_accum >> N) + (cross_sum >> N) > + + ((hilo > cross_sum) << N), > + low_accum = (xl*yl >> N) + (cross_sum & mask). */ > + { long_mul_row::HIGH_PART, PLUS_EXPR, 4, > + { { LMK_MUL_HIHI, LMX_NONE }, > + { LMK_CROSS_SUM, LMX_HI }, > + { LMK_LOW_ACCUM, LMX_HI }, > + { LMK_CARRY_CROSS_SUM, LMX_NONE } }, > + NULL }, > + /* LOW-PART fold. Recover the lower 2N bits from xl*yl plus a > + shifted cross-half term. Notation as for the HIGH-PART row above. */ > + /* (xl*yl & mask) | (low_accum << N), > + low_accum = (xl*yl >> N) + (cross_sum & mask). */ > + { long_mul_row::LOW_PART, BIT_IOR_EXPR, 2, > + { { LMK_MUL_LOLO, LMX_LO }, > + { LMK_LOW_ACCUM, LMX_SHL_N } }, > + NULL }, > +}; > + > +/* If a multi-used inner addition (sharing the chain's outer code) blocked > + linearization of a long-mul candidate, emit a dump-file hint pointing > + at it. */ > + > +static void > +long_mul_hint_shared_intermediate (gimple *shared_def) seems there is one caller? if that remains through the series please inline > +{ > + if (!shared_def || !dump_file || !(dump_flags & TDF_DETAILS)) > + return; > + fprintf (dump_file, "long-mul fold rejected: shared intermediate at "); > + print_gimple_stmt (dump_file, shared_def, 0, TDF_SLIM); > +} > + > +/* Top-level entry for long-multiply folding. Walks STMT's outer > + addition or BIT_IOR chain, classifies the summands, and dispatches > + to create_mul_high_seq / create_mul_low_seq if the multiset matches > + a known long-multiply form. Returns true on success. */ > + > +static bool > +match_long_mul (gimple *stmt) Pass in a gassign * here > +{ > + if (!is_gimple_assign (stmt)) > + return false; makes this redundant. > + tree_code outer = gimple_assign_rhs_code (stmt); > + if (outer != PLUS_EXPR && outer != BIT_IOR_EXPR) > + return false; > + > + /* Skip non-candidate adds (signed, pointer, odd-width) before walking the > + chain. No legitimate long-mul leaf has a type the atoms would reject; > + this just avoids the linearize/classify work on every other PLUS/IOR. > */ > + tree lhs_type = TREE_TYPE (gimple_get_lhs (stmt)); gimple_assign_lhs (stmt) > + if (!INTEGRAL_TYPE_P (lhs_type) > + || !TYPE_UNSIGNED (lhs_type) > + || TYPE_PRECISION (lhs_type) % 2 != 0) > + return false; > + > + auto_vec<tree, LONG_MUL_MAX_SUMMANDS + 1> leaves; > + gimple *shared_def = NULL; > + if (!long_mul_linearize_chain (stmt, outer, leaves, &shared_def)) > + return false; > + if (leaves.length () < 2) > + return false; > + > + auto_vec<long_mul_summand, LONG_MUL_MAX_SUMMANDS> summands; > + for (tree leaf : leaves) > + { > + long_mul_summand s; > + if (!long_mul_classify_summand (leaf, &s)) > + { > + long_mul_hint_shared_intermediate (shared_def); > + return false; > + } > + summands.quick_push (s); > + } > + summands.qsort (long_mul_summand_compare); > + > + /* HIGH_PART rows emit a 2N-bit multiply that is consumed by > + pass_optimize_widening_mul (WIDEN_MULT_EXPR conversion or > + longhand re-synthesis) or by expand (supported 2N mode); > + LOW_PART rows emit a plain MULT_EXPR. Emission needs only a 2N > + mode to exist in the mode table -- capability is settled on the > + lowering side. */ > + scalar_int_mode mode, wide_mode; > + bool can_emit_high > + = is_a <scalar_int_mode> (TYPE_MODE (lhs_type), &mode) > + && GET_MODE_2XWIDER_MODE (mode).exists (&wide_mode); > + > + for (const long_mul_row &row : long_mul_table) > + { > + if (row.outer != outer > + || (row.part == long_mul_row::HIGH_PART && !can_emit_high) > + || !long_mul_signature_matches (summands, row)) > + continue; > + > + tree op0, op1; > + if (!long_mul_check_consistency (summands, &op0, &op1)) > + continue; > + > + /* Do not emit the wide chain when an operand is subject to > + abnormal coalescing: the widening_mul-side consumers refuse > + such operands (see convert_mult_to_widen), which would leave > + the chain without a consumer. */ > + if (row.part == long_mul_row::HIGH_PART > + && ((TREE_CODE (op0) == SSA_NAME > + && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (op0)) > + || (TREE_CODE (op1) == SSA_NAME > + && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (op1)))) > + continue; > + > + if (row.extra_check && !row.extra_check (summands, stmt)) > + continue; > + > + if (row.part == long_mul_row::HIGH_PART) > + { > + create_mul_high_seq (op0, op1, stmt); > + if (dump_file && (dump_flags & TDF_DETAILS)) > + fprintf (dump_file, "Long multiplication high part folded.\n"); > + return true; > + } > + create_mul_low_seq (op0, op1, stmt); > + if (dump_file && (dump_flags & TDF_DETAILS)) > + fprintf (dump_file, "Long multiplication low part folded.\n"); > + return true; > + } > + > + long_mul_hint_shared_intermediate (shared_def); > + return false; > +} > > /* Determine whether applying the 2 permutations (mask1 then mask2) > gives back one of the input. */ > @@ -5851,11 +6538,15 @@ pass_forwprop::execute (function *fun) > } > else if (TREE_CODE_CLASS (code) == tcc_comparison) > changed |= forward_propagate_into_comparison (&gsi); > - else if ((code == PLUS_EXPR > - || code == BIT_IOR_EXPR > - || code == BIT_XOR_EXPR) > - && simplify_rotate (&gsi)) > - changed = true; > + else if ((code == PLUS_EXPR || code == BIT_IOR_EXPR)) > + { > + bool folded = match_long_mul (stmt); > + if (!folded) > + folded = simplify_rotate (&gsi); > + changed |= folded; > + } > + else if (code == BIT_XOR_EXPR) > + changed |= simplify_rotate (&gsi); > else if (code == VEC_PERM_EXPR) > changed |= simplify_permutation (&gsi); > else if (code == CONSTRUCTOR > -- > 2.55.0 >
