https://gcc.gnu.org/g:bddc41e290113dd9160b01f2fdf925a1876c8ee0
commit r16-2136-gbddc41e290113dd9160b01f2fdf925a1876c8ee0
Author: Richard Sandiford <richard.sandif...@arm.com>
Date: Wed Jul 9 14:59:34 2025 +0100
ext-dce: Fix subreg_lsb is_constant assumption (2)
This patch fixes another instance of the problem described in the
cover note for g:bf3037e923e9f91d93ab64bdf73a37f64f659fb9.
gcc/
* ext-dce.cc (ext_dce_process_uses): Apply is_constant directly
to the subreg_lsb.
Diff:
---
gcc/ext-dce.cc | 4 +---
1 file changed, 1 insertion(+), 3 deletions(-)
diff --git a/gcc/ext-dce.cc b/gcc/ext-dce.cc
index e7635fb7a394..67ec92a42878 100644
--- a/gcc/ext-dce.cc
+++ b/gcc/ext-dce.cc
@@ -757,7 +757,7 @@ ext_dce_process_uses (rtx_insn *insn, rtx obj,
and process the inner object. */
if (paradoxical_subreg_p (y))
y = XEXP (y, 0);
- else if (SUBREG_P (y) && SUBREG_BYTE (y).is_constant ())
+ else if (SUBREG_P (y) && subreg_lsb (y).is_constant (&bit))
{
/* If !TRULY_NOOP_TRUNCATION_MODES_P, the mode
change performed by Y would normally need to be a
@@ -774,8 +774,6 @@ ext_dce_process_uses (rtx_insn *insn, rtx obj,
GET_MODE (SUBREG_REG (y))))))
break;
- bit = subreg_lsb (y).to_constant ();
-
/* If this is a wide object (more bits than we can fit
in a HOST_WIDE_INT), then just break from the SET
context. That will cause the iterator to walk down
