[gcc r15-10524] strlen: Fixup load alignment for memcmp

[Andrew Pinski]

https://gcc.gnu.org/g:21866f27110c1d6370f66050b9fa4fafb0a4f01b

commit r15-10524-g21866f27110c1d6370f66050b9fa4fafb0a4f01b
Author: Andrew Pinski <andrew.pinski@oss.qualcomm.com>
Date:   Tue Sep 2 13:57:26 2025 -0700

    strlen: Fixup load alignment for memcmp
    
    Like the previous commit but for strlen copy so we can backport
    this commit. The loads should have the correct alignment on them
    so we need to create newly aligned types when the alignment of the
    pointer is less than the alignment of the current type.
    
    Pushed as pre-approved by https://gcc.gnu.org/pipermail/gcc-patches/2025-September/694016.html
    after a bootstrap/test on x86_64-linux-gnu.
    
            PR tree-optimization/121776
    gcc/ChangeLog:
    
            * tree-ssa-strlen.cc (strlen_pass::handle_builtin_memcmp): Create
            unaligned types if the alignment of the pointers is less
            than the alignment of the new type.
    
    Signed-off-by: Andrew Pinski <andrew.pinski@oss.qualcomm.com>
    (cherry picked from commit caa1c2f42691d68af4d894a5c3e700ecd2dba080)

Diff:
---
 gcc/tree-ssa-strlen.cc | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/gcc/tree-ssa-strlen.cc b/gcc/tree-ssa-strlen.cc
index c4d64132e538..3cef33bf5b07 100644
--- a/gcc/tree-ssa-strlen.cc
+++ b/gcc/tree-ssa-strlen.cc
@@ -4009,8 +4009,16 @@ strlen_pass::handle_builtin_memcmp ()
 	  tree ptrtype = build_pointer_type_for_mode (char_type_node,
 						      ptr_mode, true);
 	  off = build_int_cst (ptrtype, 0);
-	  arg1 = build2_loc (loc, MEM_REF, type, arg1, off);
-	  arg2 = build2_loc (loc, MEM_REF, type, arg2, off);
+
+	  /* Create unaligned types if needed. */
+	  tree type1 = type, type2 = type;
+	  if (TYPE_ALIGN (type1) > align1)
+	    type1 = build_aligned_type (type1, align1);
+	  if (TYPE_ALIGN (type2) > align2)
+	    type2 = build_aligned_type (type2, align2);
+
+	  arg1 = build2_loc (loc, MEM_REF, type1, arg1, off);
+	  arg2 = build2_loc (loc, MEM_REF, type2, arg2, off);
 	  tree tem1 = fold_const_aggregate_ref (arg1);
 	  if (tem1)
 	    arg1 = tem1;