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.

1 files changed, 14 insertions, 0 deletions

diff --git a/gcc/testsuite/gcc.dg/gomp/pr100508.c b/gcc/testsuite/gcc.dg/gomp/pr100508.c
new file mode 100644
index 0000000..c3fa2fc
--- /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;
+}