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arm: don't allow movMcc when short-it but no vsel [PR124134]

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Perverse combinations of options can lead to the compiler having to
work around unexpected situations.  Armv8 originally specified that
complex IT sequences were deprecated for performance (it was later
rescinded).  If the options restrict the floating-point unit to
one without vsel, then movMcc patterns need complex IT sequences
and we can end up with unmatched RTL patterns.  Avoid this by
failing early when the target patterns are disabled.

gcc/ChangeLog:

	PR target/124134
	* config/arm/arm.md (movsfcc): FAIL if using restricted IT
	blocks and we lack VSEL.
	(movdfcc): Likewise.

gcc/testsuite/ChangeLog:

	PR target/124134
	* gcc.target/arm/pr124134.c: New test.

(cherry picked from commit 06221fe413)
This commit is contained in:
Richard Earnshaw
2026-02-17 16:19:32 +00:00
parent 2601d040a8
commit d6c051485b
2 changed files with 20 additions and 2 deletions
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12
gcc/config/arm/arm.md
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@@ -8393,9 +8393,13 @@
enum rtx_code code = GET_CODE (operands[1]);
rtx ccreg;
/* Perverse combinations of architecture options can't be supported
as they need conditional instructions. */
if (TARGET_THUMB2 && arm_restrict_it && !TARGET_VFP5)
FAIL;
if (!arm_validize_comparison (&operands[1], &XEXP (operands[1], 0),
&XEXP (operands[1], 1)))
FAIL;
FAIL;
code = GET_CODE (operands[1]);
ccreg = arm_gen_compare_reg (code, XEXP (operands[1], 0),
@@ -8415,9 +8419,13 @@
enum rtx_code code = GET_CODE (operands[1]);
rtx ccreg;
/* Perverse combinations of architecture options can't be supported
as they need conditional instructions. */
if (TARGET_THUMB2 && arm_restrict_it && !TARGET_VFP5)
FAIL;
if (!arm_validize_comparison (&operands[1], &XEXP (operands[1], 0),
&XEXP (operands[1], 1)))
FAIL;
FAIL;
code = GET_CODE (operands[1]);
ccreg = arm_gen_compare_reg (code, XEXP (operands[1], 0),
XEXP (operands[1], 1), NULL_RTX);

10
gcc/testsuite/gcc.target/arm/pr124134.c Normal file
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@@ -0,0 +1,10 @@
/* { dg-do compile } */
/* { dg-require-effective-target arm_arch_v7a_fp_hard_ok } */
/* { dg-add-options arm_arch_v7a_fp_hard } */
/* { dg-additional-options "-O2 -mrestrict-it" } */
double max___a, max___b;
double max() {
if (max___a < max___b)
return max___b;
return max___a;
}