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.
Backported after 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 <amacl...@redhat.com>
(cherry picked from commit 6a5cb782d1486b378d70857c8efae558da0eb2cc)
---
.../gcc.c-torture/compile/dce-inline-asm-1.c | 15 +++++++++++++++
.../gcc.c-torture/compile/dce-inline-asm-2.c | 16 ++++++++++++++++
gcc/testsuite/gcc.dg/tree-ssa/pr108684-1.c | 18 ++++++++++++++++++
gcc/tree-ssa-dce.cc | 5 +++--
4 files changed, 52 insertions(+), 2 deletions(-)
create mode 100644 gcc/testsuite/gcc.c-torture/compile/dce-inline-asm-1.c
create mode 100644 gcc/testsuite/gcc.c-torture/compile/dce-inline-asm-2.c
create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/pr108684-1.c
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 00000000000..a9f02e44bd7
--- /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 00000000000..a41b16e4bd0
--- /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
index 00000000000..3ba206f765e
--- /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 4b7b664867d..4fa830dffd3 100644
--- a/gcc/tree-ssa-dce.cc
+++ b/gcc/tree-ssa-dce.cc
@@ -2062,9 +2062,9 @@ 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
@@ -2094,6 +2094,7 @@ simple_dce_from_worklist (bitmap worklist)
remove_phi_node (&gsi, true);
else
{
+ unlink_stmt_vdef (t);
gsi_remove (&gsi, true);
release_defs (t);
}
--
2.17.1
