[gcc r16-3491] tree-optimization/121744 - handle CST << var in shift pattern recog

[Richard Biener via Gcc-cvs]

https://gcc.gnu.org/g:20cd438f2f49ed4816cba9ecc558ee3377b342ba

commit r16-3491-g20cd438f2f49ed4816cba9ecc558ee3377b342ba
Author: Richard Biener <rguent...@suse.de>
Date:   Mon Sep 1 13:29:23 2025 +0200

    tree-optimization/121744 - handle CST << var in shift pattern recog
    
    We currently do not handle promotion/demotion of 'var' when the
    left operand of a variable shift is constant.  There's no good
    reason why, so the following fixes this omission.
    
            PR tree-optimization/121744
            * tree-vect-patterns.cc (vect_recog_vector_vector_shift_pattern):
            Allow constant left operand.
    
            * gcc.dg/vect/pr121744-1.c: New testcase.

Diff:
---
 gcc/testsuite/gcc.dg/vect/pr121744-1.c | 13 +++++++++++++
 gcc/tree-vect-patterns.cc              |  3 +--
 2 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/gcc/testsuite/gcc.dg/vect/pr121744-1.c 
b/gcc/testsuite/gcc.dg/vect/pr121744-1.c
new file mode 100644
index 000000000000..81f499662cdb
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/vect/pr121744-1.c
@@ -0,0 +1,13 @@
+/* { dg-do compile } */
+/* { dg-additional-options "-mavx2" { target avx2 } } */
+
+unsigned long a[1024];
+unsigned int b[1024];
+
+void foo()
+{
+  for (int i = 0; i < 1024; ++i)
+    a[i] = 1ul << b[i];
+}
+
+/* { dg-final { scan-tree-dump "vectorized 1 loops" "vect" { target 
vect_var_shift } } } */
diff --git a/gcc/tree-vect-patterns.cc b/gcc/tree-vect-patterns.cc
index 65704e5f338c..16694d7991cd 100644
--- a/gcc/tree-vect-patterns.cc
+++ b/gcc/tree-vect-patterns.cc
@@ -4077,8 +4077,7 @@ vect_recog_vector_vector_shift_pattern (vec_info *vinfo,
   lhs = gimple_assign_lhs (last_stmt);
   oprnd0 = gimple_assign_rhs1 (last_stmt);
   oprnd1 = gimple_assign_rhs2 (last_stmt);
-  if (TREE_CODE (oprnd0) != SSA_NAME
-      || TREE_CODE (oprnd1) != SSA_NAME
+  if (TREE_CODE (oprnd1) != SSA_NAME
       || TYPE_MODE (TREE_TYPE (oprnd0)) == TYPE_MODE (TREE_TYPE (oprnd1))
       || !INTEGRAL_TYPE_P (TREE_TYPE (oprnd0))
       || !type_has_mode_precision_p (TREE_TYPE (oprnd1))