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regcprop: Return early in maybe_mode_change for unorder modes [PR124649]

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Like r16-727-g2ec5082dd24cef but the call to partial_subreg_p happens
in a later place, maybe_mode_change.
For this example we have VNx4QImode and DImode which are not ordered.

Bootstrapped and tested on aarch64-linux-gnu.

	PR rtl-optimization/124649

gcc/ChangeLog:

	* regcprop.cc (maybe_mode_change): Return early
	for unordered modes.

gcc/testsuite/ChangeLog:

	* gcc.dg/torture/pr124649-1.c: New test.

Signed-off-by: Andrew Pinski <andrew.pinski@oss.qualcomm.com>
This commit is contained in:
Andrew Pinski
2026-03-26 13:21:01 -07:00
parent 8df8a196f7
commit af787f951b
2 changed files with 23 additions and 0 deletions
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8
gcc/regcprop.cc
View File

@@ -431,6 +431,14 @@ maybe_mode_change (machine_mode orig_mode, machine_mode copy_mode,
machine_mode new_mode, unsigned int regno,
unsigned int copy_regno ATTRIBUTE_UNUSED)
{
/* All three modes precision have to be ordered to each other,
otherwise partial_subreg_p won't work. */
if (!ordered_p (GET_MODE_PRECISION (orig_mode),
GET_MODE_PRECISION (copy_mode))
|| !ordered_p (GET_MODE_PRECISION (copy_mode),
GET_MODE_PRECISION (new_mode)))
return NULL_RTX;
if (partial_subreg_p (copy_mode, orig_mode)
&& partial_subreg_p (copy_mode, new_mode))
return NULL_RTX;

15
gcc/testsuite/gcc.dg/torture/pr124649-1.c Normal file
View File

@@ -0,0 +1,15 @@
/* PR rtl-optimization/124649 */
/* { dg-do compile } */
/* { dg-additional-options "-mcpu=neoverse-v1" { target aarch64*-*-* } } */
void f(char *g, int b) {
int k = b & 4 + 1;
int c[b];
if (k == 1)
b >>= 3;
b &= 1;
c[0] = b;
for (int i = 0; i < k; i++)
g[i] = c[i];
}