[PATCH] Fix RTL DCE ICE (PR rtl-optimization/90082)

[Jakub Jelinek]

Hi!

Recently I've added an assert that if !can_alter_cfg DCE (fast DCE in that
case) doesn't actually alter the cfg.  The following testcase shows
something where it still does.  Even when a (const or pure) call doesn't
throw, it could have EDGE_ABNORMAL{,_CALL} edges added to setjmp etc.
The following patch makes sure we don't DCE such calls either if we can't
alter the cfg.

Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

2019-04-16  Jakub Jelinek  <ja...@redhat.com>

        PR rtl-optimization/90082
        * dce.c (can_delete_call): New function.
        (deletable_insn_p, mark_insn): Use it.

        * gcc.dg/pr90082.c: New test.

--- gcc/dce.c.jj        2019-04-12 18:19:47.134165696 +0200
+++ gcc/dce.c   2019-04-15 12:17:40.746266503 +0200
@@ -87,6 +87,32 @@ deletable_insn_p_1 (rtx body)
     }
 }
 
+/* Don't delete calls that may throw if we cannot do so.  */
+
+static bool
+can_delete_call (rtx_insn *insn)
+{
+  if (cfun->can_delete_dead_exceptions && can_alter_cfg)
+    return true;
+  if (!insn_nothrow_p (insn))
+    return false;
+  if (can_alter_cfg)
+    return true;
+  /* If we can't alter cfg, even when the call can't throw exceptions, it
+     might have EDGE_ABNORMAL_CALL edges and so we shouldn't delete such
+     calls.  */
+  gcc_assert (CALL_P (insn));
+  if (BLOCK_FOR_INSN (insn) && BB_END (BLOCK_FOR_INSN (insn)) == insn)
+    {
+      edge e;
+      edge_iterator ei;
+
+      FOR_EACH_EDGE (e, ei, BLOCK_FOR_INSN (insn)->succs)
+       if ((e->flags & EDGE_ABNORMAL_CALL) != 0)
+         return false;
+    }
+  return true;
+}
 
 /* Return true if INSN is a normal instruction that can be deleted by
    the DCE pass.  */
@@ -111,8 +137,7 @@ deletable_insn_p (rtx_insn *insn, bool f
       && (RTL_CONST_OR_PURE_CALL_P (insn)
          && !RTL_LOOPING_CONST_OR_PURE_CALL_P (insn))
       /* Don't delete calls that may throw if we cannot do so.  */
-      && ((cfun->can_delete_dead_exceptions && can_alter_cfg)
-         || insn_nothrow_p (insn)))
+      && can_delete_call (insn))
     return find_call_stack_args (as_a <rtx_call_insn *> (insn), false,
                                 fast, arg_stores);
 
@@ -206,8 +231,7 @@ mark_insn (rtx_insn *insn, bool fast)
          && !SIBLING_CALL_P (insn)
          && (RTL_CONST_OR_PURE_CALL_P (insn)
              && !RTL_LOOPING_CONST_OR_PURE_CALL_P (insn))
-         && ((cfun->can_delete_dead_exceptions && can_alter_cfg)
-             || insn_nothrow_p (insn)))
+         && can_delete_call (insn))
        find_call_stack_args (as_a <rtx_call_insn *> (insn), true, fast, NULL);
     }
 }
--- gcc/testsuite/gcc.dg/pr90082.c.jj   2019-04-15 12:22:01.662053468 +0200
+++ gcc/testsuite/gcc.dg/pr90082.c      2019-04-15 12:22:41.638407968 +0200
@@ -0,0 +1,13 @@
+/* PR rtl-optimization/90082 */
+/* { dg-do compile } */
+/* { dg-options "-O1 -fnon-call-exceptions -ftrapv" } */
+
+void *buf[5];
+
+void
+foo (int a)
+{
+  if (__builtin_setjmp (buf) == 0)
+    __asm__ ("" : : "n" (a * 2));      /* { dg-error "impossible constraint in 
'asm'" } */
+                                       /* { dg-warning "asm operand 0 probably 
doesn't match constraints" "" { target *-*-* } .-1 } */
+}

        Jakub