AMD General Hi Richard,
> -----Original Message----- > From: Richard Biener <[email protected]> > Sent: Monday, October 5, 2026 7:25 PM > To: [email protected] > Cc: [email protected] > Subject: [PATCH] [x86][v2] umul<mode>3_highpart for VnDI > > Caution: This message originated from an External Source. Use proper caution > when opening attachments, clicking links, or responding. > > > This implements umul<mode>3_highpart for V2DI, V4DI and V8DI using > SSE2 instructions, specifically exercising pmuludq. I wasn't able to produce > a > scalar vectorizer pattern open-coding a sequence that would vectorize to this, > specifically with the same VF and the setup of the input to the pmuludq, so I > opted for implementing this in the target. > > I added a testcase for a V2DI loop that shouldn't be vectorized and one for a > V4DI loop that should. > > This speeds up 750.sealcrypto_r by ~20% on Zen4 and should recover what was > lost with r17-3437. > > v2: > - merge the two function costing parts, use SImode multiplication cost, > VnDImode multiplication cost is not accurate for the SImode widening > multiplication we want to use > - add similar costing to the MULT_HIGHPART_EXPR case > - alternate multiplication sequence, squeezing out a few ops > > Bootstrapped on x86_64-unknown-linux-gnu, testing in progress. > > I have re-measured this with 750.sealcrypto_r and the alternate multiplication > sequence is about 1.5% faster, overall it's still a ~20% win. > > OK for trunk if testing passes? > > Thanks, > Richard. > > PR tree-optimization/127452 > * config/i386/i386-protos.h (ix86_expand_umulvndi_highpart): Declare. > * config/i386/i386-expand.cc (ix86_expand_umulvndi_highpart): > New function. > * config/i386/sse.md (umul<mode>3_highpart): Add for > VI8_AVX2_AVX512F. > * config/i386/i386.cc (ix86_vector_costs::add_stmt_cost): Cost > IFN_MULH as we implement it. > > * gcc.target/i386/vect-umulv2di_high.c: New testcase. > * gcc.target/i386/vect-umulv4di_high.c: Likewise. > --- > gcc/config/i386/i386-expand.cc | 67 +++++++++++++++ > gcc/config/i386/i386-protos.h | 1 + > gcc/config/i386/i386.cc | 82 +++++++++++-------- > gcc/config/i386/sse.md | 11 +++ > .../gcc.target/i386/vect-umulv2di_high.c | 14 ++++ > .../gcc.target/i386/vect-umulv4di_high.c | 12 +++ > 6 files changed, 154 insertions(+), 33 deletions(-) create mode 100644 > gcc/testsuite/gcc.target/i386/vect-umulv2di_high.c > create mode 100644 gcc/testsuite/gcc.target/i386/vect-umulv4di_high.c > > diff --git a/gcc/config/i386/i386-expand.cc b/gcc/config/i386/i386-expand.cc > index 9e112d01734..a81993c29c5 100644 > --- a/gcc/config/i386/i386-expand.cc > +++ b/gcc/config/i386/i386-expand.cc > @@ -28467,6 +28467,73 @@ ix86_expand_sse2_mulvxdi3 (rtx op0, rtx op1, rtx > op2) > gen_rtx_MULT (mode, op1, op2)); } > > +void > +ix86_expand_umulvndi_highpart (rtx op0, rtx op1, rtx op2) { > + /* The following sequence can be used with SSE2. */ > + machine_mode mode = GET_MODE (op0); > + rtx (*umul) (rtx, rtx, rtx); > + machine_mode nmode; > + if (mode == V2DImode) > + { > + umul = gen_vec_widen_umult_even_v4si; > + nmode = V4SImode; > + } > + else if (mode == V4DImode) > + { > + umul = gen_vec_widen_umult_even_v8si; > + nmode = V8SImode; > + } > + else if (mode == V8DImode) > + { > + umul = gen_vec_widen_umult_even_v16si; > + nmode = V16SImode; > + } > + else > + gcc_unreachable (); > + > + rtx t32 = GEN_INT (32); > + > + /* Shift input vectors right 32 bits so we can get high parts of > + operands. */ rtx op1_hi = expand_binop (mode, lshr_optab, op1, t32, > + NULL, 1, OPTAB_DIRECT); rtx op2_hi = expand_binop (mode, lshr_optab, > + op2, t32, NULL, 1, OPTAB_DIRECT); > + > + /* Multiply low parts. */ > + rtx p0 = gen_reg_rtx (mode); > + emit_insn (umul (p0, gen_lowpart (nmode, op1), gen_lowpart (nmode, > + op2))); > + > + /* Multiply high parts by low parts. */ rtx p1 = gen_reg_rtx > + (mode); emit_insn (umul (p1, gen_lowpart (nmode, op1_hi), gen_lowpart > + (nmode, op2))); rtx p2 = gen_reg_rtx (mode); emit_insn (umul (p2, > + gen_lowpart (nmode, op1), gen_lowpart (nmode, op2_hi))); > + > + /* Multiply high parts. */ > + rtx p3 = gen_reg_rtx (mode); > + emit_insn (umul (p3, gen_lowpart (nmode, op1_hi), > + gen_lowpart (nmode, op2_hi))); > + > + /* Fold the carry in once cross product at a time. > + t = (p0 >> 32) + p1 */ > + rtx p0_hi = expand_binop (mode, lshr_optab, p0, t32, NULL, 1, > + OPTAB_DIRECT); rtx t = expand_binop (mode, add_optab, p0_hi, p1, > + NULL, 1, OPTAB_DIRECT); > + > + /* Extract low 32 bits of products by masking with 0xffffffff. */ > + rtx mask = gen_reg_rtx (mode); emit_insn (gen_rtx_SET (mask, > + CONSTM1_RTX (mode))); mask = expand_binop (mode, lshr_optab, mask, > + t32, NULL, 1, OPTAB_DIRECT); > + > + /* u = (t & MASK) + p2 */ > + rtx u = expand_binop (mode, and_optab, t, mask, NULL, 1, > + OPTAB_DIRECT); u = expand_binop (mode, add_optab, u, p2, NULL, 1, > + OPTAB_DIRECT); > + > + /* high = p3 + (t >> 32) + (u >> 32) */ > + rtx t_hi = expand_binop (mode, lshr_optab, t, t32, NULL, 1, > +OPTAB_DIRECT); > + rtx u_hi = expand_binop (mode, lshr_optab, u, t32, NULL, 1, > +OPTAB_DIRECT); > + rtx high = expand_binop (mode, add_optab, p3, t_hi, NULL, 1, > +OPTAB_DIRECT); > + force_expand_binop (mode, add_optab, high, u_hi, op0, 1, > +OPTAB_DIRECT); } > + > /* Return 1 if control transfer instruction INSN > should be encoded with notrack prefix. */ > > diff --git a/gcc/config/i386/i386-protos.h b/gcc/config/i386/i386-protos.h > index > 4e56bf70c8d..23f82b6239e 100644 > --- a/gcc/config/i386/i386-protos.h > +++ b/gcc/config/i386/i386-protos.h > @@ -310,6 +310,7 @@ extern void ix86_expand_mul_widen_evenodd (rtx, rtx, > rtx, bool, bool); extern void ix86_expand_mul_widen_hilo (rtx, rtx, rtx, > bool, > bool); extern void ix86_expand_sse2_mulv4si3 (rtx, rtx, rtx); extern void > ix86_expand_sse2_mulvxdi3 (rtx, rtx, rtx); > +extern void ix86_expand_umulvndi_highpart (rtx, rtx, rtx); > extern void ix86_expand_sse2_abs (rtx, rtx); extern bool > ix86_expand_vector_init_duplicate (bool, machine_mode, rtx, > rtx); diff --git > a/gcc/config/i386/i386.cc > b/gcc/config/i386/i386.cc index e9015d2427e..afe799b87dc 100644 > --- a/gcc/config/i386/i386.cc > +++ b/gcc/config/i386/i386.cc > @@ -26696,7 +26696,16 @@ ix86_vector_costs::add_stmt_cost (int count, > vect_cost_for_stmt kind, > /* For MULT_HIGHPART_EXPR, x86 only supports pmulhw, > take it as MULT_EXPR. */ > case MULT_HIGHPART_EXPR: > - stmt_cost = ix86_multiplication_cost (ix86_cost, mode); > + if (kind == vector_stmt && GET_MODE_INNER (mode) == DImode) > + { > + /* ix86_expand_umulvndi_highpart, 4 SImode -> DImode > + widening multiplies. */ > + stmt_cost = ix86_multiplication_cost (ix86_cost, SImode) * 4; > + /* 5 shifts by 32bit, 1 and, 4 adds. */ > + stmt_cost += ix86_vec_cost (mode, ix86_cost->sse_op) * 10; > + } Is this above cost changes also needed for case MULT_EXPR ?? > + else > + stmt_cost = ix86_multiplication_cost (ix86_cost, mode); > break; > /* There's no direct instruction for WIDEN_MULT_EXPR, > take emulation into account. */ @@ -26927,6 +26936,45 @@ > ix86_vector_costs::add_stmt_cost (int count, vect_cost_for_stmt kind, > break; > } > } > + else if ((kind == vector_stmt || kind == scalar_stmt) > + && stmt_info > + && stmt_info->stmt > + && is_gimple_call (stmt_info->stmt)) > + { > + tree fndecl = gimple_call_fndecl (stmt_info->stmt); > + cgraph_node *node; > + combined_fn cfn; > + if ((fndecl > + && (node = cgraph_node::get (fndecl)) > + && node->simd_clones) > + || gimple_call_internal_p (stmt_info->stmt, IFN_MASK_CALL)) > + stmt_cost = 10 * ix86_vec_cost (mode, > + mode == SFmode ? ix86_cost->fmass > + : ix86_cost->fmasd); > + else if ((cfn = gimple_call_combined_fn (stmt_info->stmt)) != CFN_LAST) > + switch (cfn) > + { > + case CFN_FMA: > + stmt_cost = ix86_vec_cost (mode, > + mode == SFmode ? ix86_cost->fmass > + : ix86_cost->fmasd); > + break; > + case CFN_MULH: > + if (kind == vector_stmt && GET_MODE_INNER (mode) == DImode) > + { > + /* ix86_expand_umulvndi_highpart, 4 SImode -> DImode > + widening multiplies. */ > + stmt_cost = ix86_multiplication_cost (ix86_cost, SImode) * 4; > + /* 5 shifts by 32bit, 1 and, 4 adds. */ > + stmt_cost += ix86_vec_cost (mode, ix86_cost->sse_op) * 10; > + } > + else > + stmt_cost = ix86_multiplication_cost (ix86_cost, mode); > + break; > + default: > + break; > + } > + } > > /* Record number of load/store/gather/scatter in vectorized body. */ > if (where == vect_body && !m_costing_for_scalar) @@ -27054,38 +27102,6 > @@ ix86_vector_costs::add_stmt_cost (int count, vect_cost_for_stmt kind, > } > } > > - > - combined_fn cfn; > - if ((kind == vector_stmt || kind == scalar_stmt) > - && stmt_info > - && stmt_info->stmt > - && is_gimple_call (stmt_info->stmt)) > - { > - tree fndecl = gimple_call_fndecl (stmt_info->stmt); > - cgraph_node *node; > - if ((fndecl > - && (node = cgraph_node::get (fndecl)) > - && node->simd_clones) > - || gimple_call_internal_p (stmt_info->stmt, IFN_MASK_CALL)) > - stmt_cost = 10 * ix86_vec_cost (mode, > - mode == SFmode ? ix86_cost->fmass > - : ix86_cost->fmasd); > - else if ((cfn = gimple_call_combined_fn (stmt_info->stmt)) != CFN_LAST) > - switch (cfn) > - { > - case CFN_FMA: > - stmt_cost = ix86_vec_cost (mode, > - mode == SFmode ? ix86_cost->fmass > - : ix86_cost->fmasd); > - break; > - case CFN_MULH: > - stmt_cost = ix86_multiplication_cost (ix86_cost, mode); > - break; > - default: > - break; > - } > - } > - > if (kind == vec_promote_demote) > { > int outer_size > diff --git a/gcc/config/i386/sse.md b/gcc/config/i386/sse.md index > 2b6d7de1f7f..c1e8b256295 100644 > --- a/gcc/config/i386/sse.md > +++ b/gcc/config/i386/sse.md > @@ -17404,6 +17404,17 @@ > (set_attr "prefix" "orig,vex") > (set_attr "mode" "<sseinsnmode>")]) > > +(define_expand "umul<mode>3_highpart" > + [(set (match_operand:VI8_AVX2_AVX512F 0 "register_operand") > + (umul_highpart:VI8_AVX2_AVX512F > + (match_operand:VI8_AVX2_AVX512F 1 "vector_operand") > + (match_operand:VI8_AVX2_AVX512F 2 "vector_operand")))] > + "TARGET_SSE2" > +{ > + ix86_expand_umulvndi_highpart (operands[0], operands[1], > +operands[2]); > + DONE; > +}) > + > (define_expand "vec_widen_umult_even_v16si<mask_name>" > [(set (match_operand:V8DI 0 "register_operand") > (mult:V8DI > diff --git a/gcc/testsuite/gcc.target/i386/vect-umulv2di_high.c > b/gcc/testsuite/gcc.target/i386/vect-umulv2di_high.c > new file mode 100644 > index 00000000000..ca839983dc9 > --- /dev/null > +++ b/gcc/testsuite/gcc.target/i386/vect-umulv2di_high.c > @@ -0,0 +1,14 @@ > +/* { dg-do compile { target { ! ia32 } } } */ > +/* { dg-options "-O2 -msse2 -mno-avx" } */ > + > +#include <stdint.h> > + > +void mulu64_high (uint64_t * __restrict r, uint64_t *a, uint64_t *b) { > + for (int i = 0; i < 128; ++i) > + r[i] = ((unsigned __int128)a[i] * (unsigned __int128)b[i]) >> 64; } > + > +/* Vectorizing two 64bit unsigned highpart multiplies with 4 pmuludq plus > + more is slower than two iterations with a mulq each. */ > +/* { dg-final { scan-assembler-times "pmuludq" 0 } } */ > diff --git a/gcc/testsuite/gcc.target/i386/vect-umulv4di_high.c > b/gcc/testsuite/gcc.target/i386/vect-umulv4di_high.c > new file mode 100644 > index 00000000000..ef966b4ec07 > --- /dev/null > +++ b/gcc/testsuite/gcc.target/i386/vect-umulv4di_high.c > @@ -0,0 +1,12 @@ > +/* { dg-do compile { target { ! ia32 } } } */ > +/* { dg-options "-O2 -mavx2 -mprefer-vector-width=256" } */ > + > +#include <stdint.h> > + > +void mulu64_high (uint64_t * __restrict r, uint64_t *a, uint64_t *b) { > + for (int i = 0; i < 128; ++i) > + r[i] = ((unsigned __int128)a[i] * (unsigned __int128)b[i]) >> 64; } > + > +/* { dg-final { scan-assembler-times "pmuludq" 4 } } */ > -- > 2.51.0 Regards, Venkat.
