[gcc r14-8796] target/113255 - avoid REG_POINTER on a pointer difference

[Richard Biener <rguenth@gcc.gnu.org>]

https://gcc.gnu.org/g:5b281946c4b51132caf5e5b64c730fef92dd6123

commit r14-8796-g5b281946c4b51132caf5e5b64c730fef92dd6123
Author: Richard Biener <rguenther@suse.de>
Date:   Thu Feb 1 13:54:11 2024 +0100

    target/113255 - avoid REG_POINTER on a pointer difference
    
    The following avoids re-using a register holding a pointer (and
    thus might be REG_POINTER) for the result of a pointer difference
    computation.  That might confuse heuristics in (broken) RTL alias
    analysis which relies on REG_POINTER indicating that we're
    dealing with one.
    
    This alone doesn't fix anything.
    
            PR target/113255
            * config/i386/i386-expand.cc
            (expand_set_or_cpymem_prologue_epilogue_by_misaligned_moves):
            Use a new pseudo for the skipped number of bytes.

Diff:
---
 gcc/config/i386/i386-expand.cc | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/gcc/config/i386/i386-expand.cc b/gcc/config/i386/i386-expand.cc
index 5706220823ab..50f9fe2c0d73 100644
--- a/gcc/config/i386/i386-expand.cc
+++ b/gcc/config/i386/i386-expand.cc
@@ -8429,7 +8429,7 @@ expand_set_or_cpymem_prologue_epilogue_by_misaligned_moves (rtx destmem, rtx src
       /* See how many bytes we skipped.  */
       saveddest = expand_simple_binop (GET_MODE (*destptr), MINUS, saveddest,
 				       *destptr,
-				       saveddest, 1, OPTAB_DIRECT);
+				       NULL_RTX, 1, OPTAB_DIRECT);
       /* Adjust srcptr and count.  */
       if (!issetmem)
 	*srcptr = expand_simple_binop (GET_MODE (*srcptr), MINUS, *srcptr,