On Mon, 23 Sep 2024, Artemiy Volkov wrote:
> Implement a match.pd pattern for C1 - X cmp C2, where C1 and C2 are
> integer constants and X is of a UB-on-overflow type. The pattern is
> simplified to X rcmp C1 - C2 by moving X and C2 to the other side of the
> comparison (with opposite signs). If C1 - C2 happens to overflow,
> replace the whole expression with either a constant 0 or a constant 1
> node, depending on the comparison operator and the sign of the overflow.
>
> This transformation allows to occasionally save load-immediate /
> subtraction instructions, e.g. the following statement:
>
> 10 - (int) x <= 9;
>
> now compiles to
>
> sgt a0,a0,zero
>
> instead of
>
> li a5,10
> sub a0,a5,a0
> slti a0,a0,10
>
> on 32-bit RISC-V.
>
> Additional examples can be found in the newly added test file. This
> patch has been bootstrapped and regtested on aarch64, x86_64, and
> i386, and additionally regtested on riscv32. Existing tests were
> adjusted where necessary.
OK.
Thanks,
Richard.
> gcc/ChangeLog:
>
> PR tree-optimization/116024
> * match.pd: New transformation around integer comparison.
>
> gcc/testsuite/ChangeLog:
>
> * gcc.dg/tree-ssa/pr116024.c: New test.
> * gcc.dg/pr67089-6.c: Adjust.
>
> Signed-off-by: Artemiy Volkov <arte...@synopsys.com>
> ---
> gcc/match.pd | 26 +++++++++
> gcc/testsuite/gcc.dg/pr67089-6.c | 4 +-
> gcc/testsuite/gcc.dg/tree-ssa/pr116024.c | 74 ++++++++++++++++++++++++
> 3 files changed, 102 insertions(+), 2 deletions(-)
> create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/pr116024.c
>
> diff --git a/gcc/match.pd b/gcc/match.pd
> index 940292d0d49..81be0a21462 100644
> --- a/gcc/match.pd
> +++ b/gcc/match.pd
> @@ -8925,6 +8925,32 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
> }
> (cmp @0 { res; })))))))))
>
> +/* Invert sign of X in comparisons of the form C1 - X CMP C2. */
> +
> +(for cmp (lt le gt ge eq ne)
> + rcmp (gt ge lt le eq ne)
> + (simplify
> + (cmp (minus INTEGER_CST@0 @1) INTEGER_CST@2)
> +/* For UB-on-overflow types, simply switch sides for X and C2
> + to arrive at X RCMP C1 - C2, handling the case when the latter
> + expression overflows. */
> + (if (!TREE_OVERFLOW (@0) && !TREE_OVERFLOW (@2)
> + && TYPE_OVERFLOW_UNDEFINED (TREE_TYPE (@1)))
> + (with { tree res = int_const_binop (MINUS_EXPR, @0, @2); }
> + (if (TREE_OVERFLOW (res))
> + (switch
> + (if (cmp == NE_EXPR)
> + { constant_boolean_node (true, type); })
> + (if (cmp == EQ_EXPR)
> + { constant_boolean_node (false, type); })
> + {
> + bool less = cmp == LE_EXPR || cmp == LT_EXPR;
> + bool ovf_high = wi::lt_p (wi::to_wide (@0), 0,
> + TYPE_SIGN (TREE_TYPE (@0)));
> + constant_boolean_node (less == ovf_high, type);
> + })
> + (rcmp @1 { res; }))))))
> +
> /* Canonicalizations of BIT_FIELD_REFs. */
>
> (simplify
> diff --git a/gcc/testsuite/gcc.dg/pr67089-6.c
> b/gcc/testsuite/gcc.dg/pr67089-6.c
> index b59d75b2318..80a33c3f3e2 100644
> --- a/gcc/testsuite/gcc.dg/pr67089-6.c
> +++ b/gcc/testsuite/gcc.dg/pr67089-6.c
> @@ -57,5 +57,5 @@ T (25, unsigned short, 2U - x, if (r > 2U) foo (0))
> T (26, unsigned char, 2U - x, if (r <= 2U) foo (0))
>
> /* { dg-final { scan-tree-dump-times "ADD_OVERFLOW" 16 "widening_mul" {
> target { i?86-*-* x86_64-*-* } } } } */
> -/* { dg-final { scan-tree-dump-times "SUB_OVERFLOW" 11 "widening_mul" {
> target { { i?86-*-* x86_64-*-* } && { ! ia32 } } } } } */
> -/* { dg-final { scan-tree-dump-times "SUB_OVERFLOW" 9 "widening_mul" {
> target { { i?86-*-* x86_64-*-* } && ia32 } } } } */
> +/* { dg-final { scan-tree-dump-times "SUB_OVERFLOW" 9 "widening_mul" {
> target { { i?86-*-* x86_64-*-* } && { ! ia32 } } } } } */
> +/* { dg-final { scan-tree-dump-times "SUB_OVERFLOW" 7 "widening_mul" {
> target { { i?86-*-* x86_64-*-* } && ia32 } } } } */
> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr116024.c
> b/gcc/testsuite/gcc.dg/tree-ssa/pr116024.c
> new file mode 100644
> index 00000000000..0dde9abbf89
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/tree-ssa/pr116024.c
> @@ -0,0 +1,74 @@
> +/* PR tree-optimization/116024 */
> +/* { dg-do compile } */
> +/* { dg-options "-O1 -fdump-tree-forwprop1-details" } */
> +
> +#include <stdint.h>
> +#include <limits.h>
> +
> +uint32_t f(void);
> +
> +int32_t i1(void)
> +{
> + int32_t l = 2;
> + l = 10 - (int32_t)f();
> + return l <= 9; // f() > 0
> +}
> +
> +int32_t i1a(void)
> +{
> + int32_t l = 2;
> + l = 20 - (int32_t)f();
> + return l <= INT32_MIN; // return 0
> +}
> +
> +int32_t i1b(void)
> +{
> + int32_t l = 2;
> + l = 30 - (int32_t)f();
> + return l <= INT32_MIN + 31; // f() == INT32_MAX
> +}
> +
> +int32_t i1c(void)
> +{
> + int32_t l = 2;
> + l = INT32_MAX - 40 - (int32_t)f();
> + return l <= -38; // f() > INT32_MAX - 3
> +}
> +
> +int32_t i1d(void)
> +{
> + int32_t l = 2;
> + l = INT32_MAX - 50 - (int32_t)f();
> + return l <= INT32_MAX - 1; // f() != -50
> +}
> +
> +int32_t i1e(void)
> +{
> + int32_t l = 2;
> + l = INT32_MAX - 60 - (int32_t)f();
> + return l != INT32_MAX - 90; // f() != 30
> +}
> +
> +int32_t i1f(void)
> +{
> + int32_t l = 2;
> + l = INT32_MIN + 70 - (int32_t)f();
> + return l <= INT32_MAX - 2; // return 0
> +}
> +
> +int32_t i1g(void)
> +{
> + int32_t l = 2;
> + l = INT32_MAX/2 + 30 - (int32_t)f();
> + return l <= INT32_MIN/2 - 30; // return 1
> +}
> +
> +
> +/* { dg-final { scan-tree-dump-times "Removing dead stmt:.*?- _" 5
> "forwprop1" } } */
> +/* { dg-final { scan-tree-dump-times "return 0" 2 "forwprop1" } } */
> +/* { dg-final { scan-tree-dump-times "return 1" 1 "forwprop1" } } */
> +/* { dg-final { scan-tree-dump-times "gimple_simplified to.* > 0" 1
> "forwprop1" } } */
> +/* { dg-final { scan-tree-dump-times "gimple_simplified to.* == 2147483647"
> 1 "forwprop1" } } */
> +/* { dg-final { scan-tree-dump-times "gimple_simplified to.* > 2147483644" 1
> "forwprop1" } } */
> +/* { dg-final { scan-tree-dump-times "gimple_simplified to.* != 4294967246"
> 1 "forwprop1" } } */
> +/* { dg-final { scan-tree-dump-times "gimple_simplified to.* != 30" 1
> "forwprop1" } } */
>
--
Richard Biener <rguent...@suse.de>
SUSE Software Solutions Germany GmbH,
Frankenstrasse 146, 90461 Nuernberg, Germany;
GF: Ivo Totev, Andrew McDonald, Werner Knoblich; (HRB 36809, AG Nuernberg)
