tree-optimization: [PR108684] ICE in verify_ssa due to simple_dce_from_worklist

In simple_dce_from_worklist, we were removing an inline-asm which had a vdef.
We should not be removing inline-asm which have a vdef as this code
does not check to the store.
This fixes that oversight. This was a latent bug exposed recently
by both VRP and removal of stores to static starting to use
simple_dce_from_worklist.

Committed as approved.
Bootstrapped and tested on x86_64-linux-gnu with no regressions.

	PR tree-optimization/108684

gcc/ChangeLog:

	* tree-ssa-dce.cc (simple_dce_from_worklist):
	Check all ssa names and not just non-vdef ones
	before accepting the inline-asm.
	Call unlink_stmt_vdef on the statement before
	removing it.

gcc/testsuite/ChangeLog:

	* gcc.c-torture/compile/dce-inline-asm-1.c: New test.
	* gcc.c-torture/compile/dce-inline-asm-2.c: New test.
	* gcc.dg/tree-ssa/pr108684-1.c: New test.

co-authored-by: Andrew Macleod  <amacleod@redhat.com>

2 files changed, 31 insertions, 0 deletions

diff --git a/gcc/testsuite/gcc.c-torture/compile/dce-inline-asm-1.c b/gcc/testsuite/gcc.c-torture/compile/dce-inline-asm-1.c
new file mode 100644
index 0000000..a9f02e4
--- /dev/null
+++ b/gcc/testsuite/gcc.c-torture/compile/dce-inline-asm-1.c
@@ -0,0 +1,15 @@
+/* PR tree-optimization/108684 */
+/* This used to ICE as when we remove the store to
+   `t`, we also would remove the inline-asm which
+   had a VDEF on it but we didn't update the
+   VUSE that was later on.  */
+static int t;
+
+int f (int *a)
+{
+  int t1;
+  asm (" " : "=X" (t1) : : "memory");
+  t = t1;
+  return *a;
+}
+
diff --git a/gcc/testsuite/gcc.c-torture/compile/dce-inline-asm-2.c b/gcc/testsuite/gcc.c-torture/compile/dce-inline-asm-2.c
new file mode 100644
index 0000000..a41b16e
--- /dev/null
+++ b/gcc/testsuite/gcc.c-torture/compile/dce-inline-asm-2.c
@@ -0,0 +1,16 @@
+/* PR tree-optimization/108684 */
+/* This used to ICE as when we removed the
+   __builtin_unreachable in VRP, as we
+   would also remove the branch and the
+   inline-asm. The inline-asm had a VDEF on it,
+   which we didn't update further along and
+   not have the VDEF on the return statement
+   updated.  */
+
+int f (int a)
+{
+  asm (" " : "=X" (a) : : "memory");
+  if (a)
+    return 0;
+  __builtin_unreachable();
+}