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rtl-optimization/110867 Fix narrow comparison of memory and constant

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In certain cases a constant may not fit into the mode used to perform a
comparison.  This may be the case for sign-extended constants which are
used during an unsigned comparison as e.g. in

(set (reg:CC 100 cc)
    (compare:CC (mem:SI (reg/v/f:SI 115 [ a ]) [1 *a_4(D)+0 S4 A64])
        (const_int -2147483648 [0xffffffff80000000])))

Fixed by ensuring that the constant fits into comparison mode.

Furthermore, on some targets as e.g. sparc the constant used in a
comparison is chopped off before combine which leads to failing test
cases (see PR 110869).  Fixed by not requiring that the source mode has
to be DImode, and excluding sparc from the last two test cases entirely
since there the constant cannot be further reduced.

gcc/ChangeLog:

	PR rtl-optimization/110867
	* combine.cc (simplify_compare_const): Try the optimization only
	in case the constant fits into the comparison mode.

gcc/testsuite/ChangeLog:

	PR rtl-optimization/110869
	* gcc.dg/cmp-mem-const-1.c: Relax mode for constant.
	* gcc.dg/cmp-mem-const-2.c: Relax mode for constant.
	* gcc.dg/cmp-mem-const-3.c: Relax mode for constant.
	* gcc.dg/cmp-mem-const-4.c: Relax mode for constant.
	* gcc.dg/cmp-mem-const-5.c: Exclude sparc since here the
	constant is already reduced.
	* gcc.dg/cmp-mem-const-6.c: Exclude sparc since here the
	constant is already reduced.
This commit is contained in:
Stefan Schulze Frielinghaus 2023-08-02 21:43:22 +02:00
parent 1d5bc3285e
commit 41ef5a3416
7 changed files with 12 additions and 8 deletions
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4
gcc/combine.cc
View file

@ -11998,11 +11998,15 @@ simplify_compare_const (enum rtx_code code, machine_mode mode,
x0 >= 0x40. */
if ((code == LEU || code == LTU || code == GEU || code == GTU)
&& is_a <scalar_int_mode> (GET_MODE (op0), &int_mode)
&& HWI_COMPUTABLE_MODE_P (int_mode)
&& MEM_P (op0)
&& !MEM_VOLATILE_P (op0)
/* The optimization makes only sense for constants which are big enough
so that we have a chance to chop off something at all. */
&& (unsigned HOST_WIDE_INT) const_op > 0xff
/* Bail out, if the constant does not fit into INT_MODE. */
&& (unsigned HOST_WIDE_INT) const_op
< ((HOST_WIDE_INT_1U << (GET_MODE_PRECISION (int_mode) - 1) << 1) - 1)
/* Ensure that we do not overflow during normalization. */
&& (code != GTU || (unsigned HOST_WIDE_INT) const_op < HOST_WIDE_INT_M1U))
{

2
gcc/testsuite/gcc.dg/cmp-mem-const-1.c
View file

@ -1,6 +1,6 @@
/* { dg-do compile { target { lp64 } } } */
/* { dg-options "-O1 -fdump-rtl-combine-details" } */
/* { dg-final { scan-rtl-dump "narrow comparison from mode DI to QI" "combine" } } */
/* { dg-final { scan-rtl-dump "narrow comparison from mode .I to QI" "combine" } } */
typedef __UINT64_TYPE__ uint64_t;

2
gcc/testsuite/gcc.dg/cmp-mem-const-2.c
View file

@ -1,6 +1,6 @@
/* { dg-do compile { target { lp64 } } } */
/* { dg-options "-O1 -fdump-rtl-combine-details" } */
/* { dg-final { scan-rtl-dump "narrow comparison from mode DI to QI" "combine" } } */
/* { dg-final { scan-rtl-dump "narrow comparison from mode .I to QI" "combine" } } */
typedef __UINT64_TYPE__ uint64_t;

2
gcc/testsuite/gcc.dg/cmp-mem-const-3.c
View file

@ -1,6 +1,6 @@
/* { dg-do compile { target { lp64 } } } */
/* { dg-options "-O1 -fdump-rtl-combine-details" } */
/* { dg-final { scan-rtl-dump "narrow comparison from mode DI to HI" "combine" } } */
/* { dg-final { scan-rtl-dump "narrow comparison from mode .I to HI" "combine" } } */
typedef __UINT64_TYPE__ uint64_t;

2
gcc/testsuite/gcc.dg/cmp-mem-const-4.c
View file

@ -1,6 +1,6 @@
/* { dg-do compile { target { lp64 } } } */
/* { dg-options "-O1 -fdump-rtl-combine-details" } */
/* { dg-final { scan-rtl-dump "narrow comparison from mode DI to HI" "combine" } } */
/* { dg-final { scan-rtl-dump "narrow comparison from mode .I to HI" "combine" } } */
typedef __UINT64_TYPE__ uint64_t;

4
gcc/testsuite/gcc.dg/cmp-mem-const-5.c
View file

@ -1,6 +1,6 @@
/* { dg-do compile { target { lp64 } } } */
/* { dg-do compile { target { lp64 } && ! target { sparc*-*-* } } } */
/* { dg-options "-O1 -fdump-rtl-combine-details" } */
/* { dg-final { scan-rtl-dump "narrow comparison from mode DI to SI" "combine" } } */
/* { dg-final { scan-rtl-dump "narrow comparison from mode .I to SI" "combine" } } */
typedef __UINT64_TYPE__ uint64_t;

4
gcc/testsuite/gcc.dg/cmp-mem-const-6.c
View file

@ -1,6 +1,6 @@
/* { dg-do compile { target { lp64 } } } */
/* { dg-do compile { target { lp64 } && ! target { sparc*-*-* } } } */
/* { dg-options "-O1 -fdump-rtl-combine-details" } */
/* { dg-final { scan-rtl-dump "narrow comparison from mode DI to SI" "combine" } } */
/* { dg-final { scan-rtl-dump "narrow comparison from mode .I to SI" "combine" } } */
typedef __UINT64_TYPE__ uint64_t;