[gcc r15-1996] [alpha] adjust MEM alignment for block move [PR115459]

[Alexandre Oliva via Gcc-cvs]

https://gcc.gnu.org/g:ccfe7151803956d178947d0afda0bd66ce097275

commit r15-1996-gccfe7151803956d178947d0afda0bd66ce097275
Author: Alexandre Oliva <ol...@adacore.com>
Date:   Fri Jul 12 05:42:07 2024 -0300

    [alpha] adjust MEM alignment for block move [PR115459]
    
    Before issuing loads or stores for a block move, adjust the MEM
    alignments if analysis of the addresses enabled the inference of
    stricter alignment.  This ensures that the MEMs are sufficiently
    aligned for the corresponding insns, which avoids trouble in case of
    e.g. substitutions into SUBREGs.
    
    
    for  gcc/ChangeLog
    
            PR target/115459
            * config/alpha/alpha.cc (alpha_expand_block_move): Adjust
            MEMs to match inferred alignment.

Diff:
---
 gcc/config/alpha/alpha.cc | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/gcc/config/alpha/alpha.cc b/gcc/config/alpha/alpha.cc
index a6fe95e71778..74631a416935 100644
--- a/gcc/config/alpha/alpha.cc
+++ b/gcc/config/alpha/alpha.cc
@@ -3820,6 +3820,12 @@ alpha_expand_block_move (rtx operands[])
           else if (a >= 16 && c % 2 == 0)
            src_align = 16;
        }
+
+      if (MEM_P (orig_src) && MEM_ALIGN (orig_src) < src_align)
+       {
+         orig_src = shallow_copy_rtx (orig_src);
+         set_mem_align (orig_src, src_align);
+       }
     }
 
   tmp = XEXP (orig_dst, 0);
@@ -3841,6 +3847,12 @@ alpha_expand_block_move (rtx operands[])
           else if (a >= 16 && c % 2 == 0)
            dst_align = 16;
        }
+
+      if (MEM_P (orig_dst) && MEM_ALIGN (orig_dst) < dst_align)
+       {
+         orig_dst = shallow_copy_rtx (orig_dst);
+         set_mem_align (orig_dst, dst_align);
+       }
     }
 
   ofs = 0;