On Tue, Dec 2, 2025 at 12:11 PM Daniel Barboza
<[email protected]> wrote:
>
> Add a pattern to handle cases where we have an OP that is
> unconditionally being applied in the result of a gcond. In this case we
> can apply OP to both legs of the conditional. E.g:
>
> t = b ? 10 : 20;
> t = t + 20;
>
> becomes just:
>
> t = b ? 30 : 40
>
> PR 122608
>
> gcc/ChangeLog:
>
> * match.pd (`(c ? a : b) op d -> c ? (a op d) : (b op d)`): New
> pattern.
>
> gcc/testsuite/ChangeLog:
>
> * gcc.target/i386/pr110701.c: the pattern added is now folding
> an XOR into the ifcond, and the assembler isn't emitting an
> 'andl' anymore.
> * gcc.dg/torture/pr122608.c: New test.
>
> Signed-off-by: Daniel Barboza <[email protected]>
> ---
> gcc/match.pd | 10 +++
> gcc/testsuite/gcc.dg/torture/pr122608.c | 83 ++++++++++++++++++++++++
> gcc/testsuite/gcc.target/i386/pr110701.c | 2 +-
> 3 files changed, 94 insertions(+), 1 deletion(-)
> create mode 100644 gcc/testsuite/gcc.dg/torture/pr122608.c
>
> diff --git a/gcc/match.pd b/gcc/match.pd
> index f164ec59100..9650bbeada7 100644
> --- a/gcc/match.pd
> +++ b/gcc/match.pd
> @@ -6274,6 +6274,16 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
> && !expand_vec_cond_expr_p (TREE_TYPE (@1), TREE_TYPE (@0)))))
> (vec_cond @0 (op! @3 @1) (op! @3 @2)))))
>
> +
> +/* Non-vector comutative sink of binary ops to branches:
spelling: commutative . But these are not commutative (minus and div
are definitely not commutative) but rather just binary operators.
> + (c ? a : b) op d --> c ? (a op d) : (b op d) */
> +(for op (plus minus mult bit_and bit_ior bit_xor
> + lshift rshift rdiv trunc_div ceil_div floor_div round_div exact_div
> + trunc_mod ceil_mod floor_mod round_mod min max)
It might be useful to define a define_operator_list called tcc_binary
like what is done for tcc_comparison. And then just use that operator
list here.
> + (simplify
> + (op (cond:s @0 @1 @2) @3)
> + (cond @0 (op! @1 @3) (op! @2 @3))))
A few codes missing:
pointer_plus, pointer_diff, mult_highpart, lrotate, rrotate, complex
All comparison operators (tcc_comparison)
Some internal functions missing:
COPYSIGN, POW, XORSIGN, HYPOT
Oh I see you copied this exactly from the vector list and removed
tcc_comparison.
Note pointer_plus is not likely reduce,
pointer_diff could:
(a ? &b[0] : &b[1]) - &b[0]
which should reduce to a ? 0 : 1;
complex could too:
COMPLEX_EXPR<a ? 2.0f : 4.0f, 5.0f> -> a ? COMPLEX_CST<2.0f, 5.0f>,
COMPLEX_CST<4.0f, 5.0f>
Note these codes/internal functions can be added separately.
> +
> #if GIMPLE
> (match (nop_atomic_bit_test_and_p @0 @1 @4)
> (bit_and (convert?@4 (ATOMIC_FETCH_OR_XOR_N @2 INTEGER_CST@0 @3))
> diff --git a/gcc/testsuite/gcc.dg/torture/pr122608.c
> b/gcc/testsuite/gcc.dg/torture/pr122608.c
> new file mode 100644
> index 00000000000..f8058149e5a
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/torture/pr122608.c
> @@ -0,0 +1,83 @@
> +/* { dg-do compile } */
> +/* { dg-options "-fgimple -fdump-tree-optimized" } */
> +/* { dg-skip-if "" { *-*-* } { "-O0" "-fno-fat-lto-objects" } { "" } } */
> +
> +#define F(OP,NAME) \
> + __GIMPLE int NAME##_test(int a) \
> + { _Bool b; \
> + int t; \
> + b = a > 0; \
> + t = b ? 20 : 40; \
> + t = t OP 11; \
> + return t; }
> +
> +F (+, plus)
> +F (-, minus)
> +F (*, mult)
> +F (|, bit_ior)
> +F (^, bit_xor)
> +F (/, div)
> +F (%, mod)
> +F (<<, lshift)
> +
> +__GIMPLE int test_and(int a)
> +{
> + _Bool b;
> + int t;
> + b = a > 0;
> + t = b ? 1 : 3;
> + t = t & 3;
> + return t;
> +}
> +
> +__GIMPLE int test_rshift(int a)
> +{
> + _Bool b;
> + int t;
> + b = a > 0;
> + t = b ? 2 : 8;
> + t = t >> 1;
> + return t;
> +}
> +
> +static int min (int a, int b)
> +{
> + return a < b ? a : b;
> +}
> +
> +static int max (int a, int b)
> +{
> + return a > b ? a : b;
> +}
> +
> +__GIMPLE int min_test(int a)
> +{
> + _Bool b;
> + int t;
> + b = a > 0;
> + t = b ? 2 : 4;
> + t = min (t, 3);
> + return t;
> +}
> +
> +__GIMPLE int max_test(int a)
> +{
> + _Bool b;
> + int t;
> + b = a > 0;
> + t = b ? 2 : 4;
> + t = max (t, 3);
> + return t;
> +}
> +
> +/* { dg-final { scan-tree-dump-times " \\+ " 0 "optimized" } } */
> +/* { dg-final { scan-tree-dump-times " \\* " 0 "optimized" } } */
> +/* { dg-final { scan-tree-dump-times " \\| " 0 "optimized" } } */
> +/* { dg-final { scan-tree-dump-times " \\^ " 0 "optimized" } } */
> +/* { dg-final { scan-tree-dump-times " & " 0 "optimized" } } */
> +/* { dg-final { scan-tree-dump-times " / " 0 "optimized" } } */
> +/* { dg-final { scan-tree-dump-times " % " 0 "optimized" } } */
> +/* { dg-final { scan-tree-dump-times " << " 0 "optimized" } } */
> +/* { dg-final { scan-tree-dump-times " >> " 0 "optimized" } } */
> +/* { dg-final { scan-tree-dump-times "MIN_EXPR" 0 "optimized" } } */
> +/* { dg-final { scan-tree-dump-times "MAX_EXPR" 0 "optimized" } } */
> diff --git a/gcc/testsuite/gcc.target/i386/pr110701.c
> b/gcc/testsuite/gcc.target/i386/pr110701.c
> index 3f2cea5c3df..8cd179c3b15 100644
> --- a/gcc/testsuite/gcc.target/i386/pr110701.c
> +++ b/gcc/testsuite/gcc.target/i386/pr110701.c
> @@ -8,5 +8,5 @@ void foo() {
> *c = d(340, b >= 0) ^ 3;
> }
>
> -/* { dg-final { scan-assembler "andl\[ \\t]\\\$340," } } */
> +/* { dg-final { scan-assembler-not "andl\[ \\t]\\\$340," } } */
Changing this scan is most likely incorrect since it is looking for
wrong code. I suspect we should add a runtime testcase (that was
showing the original issue) and remove this test case instead.
Thanks,
Andrew
> /* { dg-final { scan-assembler-not "andw\[ \\t]\\\$340," } } */
> --
> 2.43.0
>
