shrink-wrap: Don't put on incoming EDGE_CROSSING [PR98289]

As mentioned in the PR, shrink-wrapping disqualifies for prologue
placement basic blocks that have EDGE_CROSSING incoming edge.
I don't see why that is necessary, those edges seem to be redirected
just fine, both on x86_64 and powerpc64.  In the former case, they
are usually conditional jumps that patch_jump_insn can handle just fine,
after all, they were previously crossing and will be crossing after
the redirection too, just to a different label.  And in the powerpc64
case, it is a simple_jump instead that again seems to be handled by
patch_jump_insn just fine.
Sure, redirecting an edge that was previously not crossing to be crossing or
vice versa can fail, but that is not what shrink-wrapping needs.
Also tested in GCC 8 with this patch and don't see ICEs there either
(though, of course, I'm not suggesting we should backport this to release
branches).
The old ICEs could have been fixed by PR87475 fix or some other one
years ago.

2020-12-17  Jakub Jelinek  <jakub@redhat.com>

	PR rtl-optimization/98289
	* shrink-wrap.c (can_get_prologue): Don't punt on EDGE_CROSSING
	incoming edges.

	* gcc.target/i386/pr98289.c: New test.
	* gcc.dg/torture/pr98289.c: New test.

diff --git a/gcc/shrink-wrap.c b/gcc/shrink-wrap.c
index d70635e94a351d2926457e752dd288fec7c9b0e7..4bb63e9b5d838174e96888163339d5970935e5be 100644 (file)
--- a/gcc/shrink-wrap.c
+++ b/gcc/shrink-wrap.c
@@ -494,7 +494,7 @@ can_get_prologue (basic_block pro, HARD_REG_SET prologue_clobbered)
   edge e;
   edge_iterator ei;
   FOR_EACH_EDGE (e, ei, pro->preds)
-    if (e->flags & (EDGE_COMPLEX | EDGE_CROSSING)
+    if (e->flags & EDGE_COMPLEX
        && !dominated_by_p (CDI_DOMINATORS, e->src, pro))
       return false;
 

diff --git a/gcc/testsuite/gcc.dg/torture/pr98289.c b/gcc/testsuite/gcc.dg/torture/pr98289.c
new file mode 100644 (file)
index 0000000..07094a1
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr98289.c
@@ -0,0 +1,52 @@
+/* PR rtl-optimization/98289 */
+/* { dg-do compile { target freorder } } */
+/* { dg-options "-O2 -freorder-blocks-and-partition" } */
+
+int bar (void) __attribute__((cold));
+
+void
+foo (int x)
+{
+  if (x)
+    __builtin_abort ();
+}
+
+void
+baz (int x)
+{
+  if (__builtin_expect (x, 0))
+    {
+      bar ();
+      bar ();
+      bar ();
+    }
+}
+
+void
+qux (int x, int y, int z, int w)
+{
+  if (x || y || z || w)
+    __builtin_abort ();
+}
+
+int
+corge (int x, int y, int z, int w, int u)
+{
+  if (__builtin_expect (x, 0))
+    goto lab;
+  u++;
+  if (__builtin_expect (y, 0))
+    goto lab;
+  u *= 2;
+  if (__builtin_expect (z, 0))
+    goto lab;
+  u |= 42;
+  if (__builtin_expect (w, 0))
+    {
+      lab:;
+      bar ();
+      bar ();
+      if (bar () > 32) goto lab;
+    }
+  return u;
+}

diff --git a/gcc/testsuite/gcc.target/i386/pr98289.c b/gcc/testsuite/gcc.target/i386/pr98289.c
new file mode 100644 (file)
index 0000000..9c620d4
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr98289.c
@@ -0,0 +1,54 @@
+/* PR rtl-optimization/98289 */
+/* { dg-do compile { target { ! ia32 } } } */
+/* { dg-require-effective-target freorder } */
+/* { dg-options "-O2 -freorder-blocks-and-partition -fdump-rtl-pro_and_epilogue-details" } */
+/* { dg-final { scan-rtl-dump-times "Performing shrink-wrapping" 4 "pro_and_epilogue" } } */
+
+int bar (void) __attribute__((cold));
+
+void
+foo (int x)
+{
+  if (x)
+    __builtin_abort ();
+}
+
+void
+baz (int x)
+{
+  if (__builtin_expect (x, 0))
+    {
+      bar ();
+      bar ();
+      bar ();
+    }
+}
+
+void
+qux (int x, int y, int z, int w)
+{
+  if (x || y || z || w)
+    __builtin_abort ();
+}
+
+int
+corge (int x, int y, int z, int w, int u)
+{
+  if (__builtin_expect (x, 0))
+    goto lab;
+  u++;
+  if (__builtin_expect (y, 0))
+    goto lab;
+  u *= 2;
+  if (__builtin_expect (z, 0))
+    goto lab;
+  u |= 42;
+  if (__builtin_expect (w, 0))
+    {
+      lab:;
+      bar ();
+      bar ();
+      if (bar () > 32) goto lab;
+    }
+  return u;
+}