commit ba374dfb937a8ac1c7c4740913331951a924f88b
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Wed May 12 10:38:35 2021 +0200

    expand: Don't reuse DEBUG_EXPRs with vector type if they have different modes [PR100508]
    
    The inliner doesn't remap DEBUG_EXPR_DECLs, so the same decls can appear
    in multiple functions.
    Furthermore, expansion reuses corresponding DEBUG_EXPRs too, so they again
    can be reused in multiple functions.
    Neither of that is a major problem, DEBUG_EXPRs are just magic value holders
    and what value they stand for is independent in each function and driven by
    what debug stmts or DEBUG_INSNs they are bound to.
    Except for DEBUG_EXPR*s with vector types, TYPE_MODE can be either BLKmode
    or some vector mode depending on whether current function's enabled ISAs
    support that vector mode or not.  On the following testcase, we expand it
    first in foo function without AVX2 enabled and so the DEBUG_EXPR is
    BLKmode, but later the same DEBUG_EXPR_DECL is used in a simd clone with
    AVX2 enabled and expansion ICEs because of a mode mismatch.
    
    The following patch fixes that by forcing recreation of a DEBUG_EXPR if
    there is a mode mismatch for vector typed DEBUG_EXPR_DECL, DEBUG_EXPRs
    will be still reused in between functions otherwise and within the same
    function the mode should be always the same.
    
    2021-05-12  Jakub Jelinek  <jakub@redhat.com>
    
            PR middle-end/100508
            * cfgexpand.c (expand_debug_expr): For DEBUG_EXPR_DECL with vector
            type, don't reuse DECL_RTL if it has different mode, instead force
            creation of a new DEBUG_EXPR.
    
            * gcc.dg/gomp/pr100508.c: New test.
    
    (cherry picked from commit 19040050aa2c8ee890fc58dda48639fc91bf0af0)

diff --git a/gcc/cfgexpand.c b/gcc/cfgexpand.c
index b1535e15d28..a7d05202184 100644
--- a/gcc/cfgexpand.c
+++ b/gcc/cfgexpand.c
@@ -4358,7 +4358,12 @@ expand_debug_expr (tree exp)
       op0 = DECL_RTL_IF_SET (exp);
 
       if (op0)
-	return op0;
+	{
+	  if (GET_MODE (op0) != mode)
+	    gcc_assert (VECTOR_TYPE_P (TREE_TYPE (exp)));
+	  else
+	    return op0;
+	}
 
       op0 = gen_rtx_DEBUG_EXPR (mode);
       DEBUG_EXPR_TREE_DECL (op0) = exp;
diff --git a/gcc/testsuite/gcc.dg/gomp/pr100508.c b/gcc/testsuite/gcc.dg/gomp/pr100508.c
new file mode 100644
index 00000000000..c3fa2fc258e
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/gomp/pr100508.c
@@ -0,0 +1,14 @@
+/* PR middle-end/100508 */
+/* { dg-do compile } */
+/* { dg-options "-O2 -g -fopenmp-simd" } */
+
+typedef int __attribute__((__vector_size__(32))) V;
+V j;
+
+#pragma omp declare simd
+int
+foo (void)
+{
+  V m = j;
+  return 0;
+}