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>

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 (file)
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 (file)
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();
+}

diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr108684-1.c b/gcc/testsuite/gcc.dg/tree-ssa/pr108684-1.c
new file mode 100644 (file)
index 0000000..3ba206f
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr108684-1.c
@@ -0,0 +1,18 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+
+
+static int t;
+
+int f (int *a)
+{
+  int t1, t2 = 0;
+  asm ("shouldshowupstill %1" : "=r" (t1), "=m"(t2) : : );
+  t = t1;
+  return t2;
+}
+
+/* Check to make sure DCE does not remove the inline-asm as it writes to t2. */
+/* We used to DCE this inline-asm when removing the store to t. */
+/* { dg-final { scan-assembler "shouldshowupstill" } } */
+/* { dg-final { scan-tree-dump-times "shouldshowupstill" 1 "optimized" } } */

diff --git a/gcc/tree-ssa-dce.cc b/gcc/tree-ssa-dce.cc
index b2fe9f4f55e2e63e0c41d2aff58b89c4b12d98ba..1f1ec2c87108693d3c42e5c36653afd90f42dc43 100644 (file)
--- a/gcc/tree-ssa-dce.cc
+++ b/gcc/tree-ssa-dce.cc
@@ -2108,9 +2108,9 @@ simple_dce_from_worklist (bitmap worklist)
 
       /* The defining statement needs to be defining only this name.
         ASM is the only statement that can define more than one
-        (non-virtual) name. */
+        name. */
       if (is_a<gasm *>(t)
-         && !single_ssa_def_operand (t, SSA_OP_DEF))
+         && !single_ssa_def_operand (t, SSA_OP_ALL_DEFS))
        continue;
 
       /* Don't remove statements that are needed for non-call
@@ -2140,6 +2140,7 @@ simple_dce_from_worklist (bitmap worklist)
        remove_phi_node (&gsi, true);
       else
        {
+         unlink_stmt_vdef (t);
          gsi_remove (&gsi, true);
          release_defs (t);
        }