[PATCH] Fix cprop ICE with conditional asserts becoming non-conditional (PR rtl-optimization/79386)

[Jakub Jelinek]

Hi!

The recent r244993 change where bypass_conditional_jumps is called only
after splitting blocks for unconditional traps can result in ICEs during
bypass_conditional_jumps, because on the (unreachable, to be removed later)
new basic blocks created by that splitting we don't have cprop per-bb data
structures like cprop_avout computed (nor space for them allocated).
bypass_conditional_jumps already uses bypass_last_basic_block variable
to avoid touching basic blocks created during that function, so this
patch just extends that to also the basic blocks created for splitting
after unconditional traps.

Bootstrapped/regtested on {x86_64,i686,powerpc64{,le}}-linux, ok for trunk?

2017-02-06  Jakub Jelinek  <ja...@redhat.com>

        PR rtl-optimization/79386
        * cprop.c (bypass_conditional_jumps): Initialize
        bypass_last_basic_block already before splitting bbs after
        unconditional traps...
        (bypass_conditional_jumps): ... rather than here.

        * gcc.c-torture/compile/pr79386.c: New test.

--- gcc/cprop.c.jj      2017-01-30 09:31:48.000000000 +0100
+++ gcc/cprop.c 2017-02-06 14:37:07.157093577 +0100
@@ -1697,7 +1697,6 @@ bypass_conditional_jumps (void)
   if (ENTRY_BLOCK_PTR_FOR_FN (cfun)->next_bb == EXIT_BLOCK_PTR_FOR_FN (cfun))
     return 0;
 
-  bypass_last_basic_block = last_basic_block_for_fn (cfun);
   mark_dfs_back_edges ();
 
   changed = 0;
@@ -1863,6 +1862,11 @@ one_cprop_pass (void)
              }
        }
 
+      /* Make sure bypass_conditional_jumps will ignore not just its new
+        basic blocks, but also the ones after unconditional traps (those are
+        unreachable and will be eventually removed as such).  */
+      bypass_last_basic_block = last_basic_block_for_fn (cfun);
+
       while (!uncond_traps.is_empty ())
        {
          rtx_insn *insn = uncond_traps.pop ();
--- gcc/testsuite/gcc.c-torture/compile/pr79386.c.jj    2017-02-06 
14:43:31.932063697 +0100
+++ gcc/testsuite/gcc.c-torture/compile/pr79386.c       2017-02-06 
14:43:19.000000000 +0100
@@ -0,0 +1,46 @@
+/* PR rtl-optimization/79386 */
+
+int a, b;
+
+int
+foo (int x)
+{
+  int c;
+  int *d, *e;
+
+  if (b == 0)
+    {
+      c = 0;
+      e = &b;
+      d = &b;
+    }
+  else
+    {
+      int f;
+
+      c = 1;
+      for (f = 0; f < 9; ++f)
+       c *= 3;
+      e = (int *) (__UINTPTR_TYPE__) c;
+      d = &x;
+    }
+  *e = c < 3;
+  if (*e != 0)
+    {
+      int g;
+
+      b += (a != 0) ? a : 1;
+      if (g != 0 || x != 0)
+       *d = 0;
+      if (b >= 0)
+       {
+         if (g != 0)
+           g = x;
+         if (*d / g != 0)
+           for (;;)
+             ;
+       }
+    }
+
+  return b * (a != 0 && *d != 0);
+}

        Jakub