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[COMMITTED] PR tree-optimization/109546 - Do not fold ADDR_EXPR conditions leading to builtin_unreachable early.

Message ID 5da330c4-2918-10df-b315-17307067d2bf@redhat.com
State New
Headers show
Series [COMMITTED] PR tree-optimization/109546 - Do not fold ADDR_EXPR conditions leading to builtin_unreachable early. | expand

Commit Message

Andrew MacLeod April 21, 2023, 8:34 p.m. UTC 
We cant represent ADDR_EXPR in ranges, so when we are processing 
builtin_unreachable() we should not be removing comparisons that utilize 
ADDR_EXPR during the early phases, or we lose some important information.

It was just an oversight that we think its a comparison to a 
representable constant.

Bootstrapped on x86_64-pc-linux-gnu with no regressions.  pushed.

This would also be suitable for the next GCC13 release when the branch 
is open.

Andrew
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Patch

commit 0afefd11e25a05dd4f8a8624e8fb046d9c85686a
Author: Andrew MacLeod <amacleod@redhat.com>
Date:   Fri Apr 21 15:03:43 2023 -0400

    Do not fold ADDR_EXPR conditions leading to builtin_unreachable early.
    
    Ranges can not represent &var globally yet, so we cannot fold these
    expressions early or we lose the __builtin_unreachable information.
    
            PR tree-optimization/109546
            gcc/
            * tree-vrp.cc (remove_unreachable::remove_and_update_globals): Do
            not fold conditions with ADDR_EXPR early.
    
            gcc/testsuite/
            * gcc.dg/pr109546.c: New.

diff --git a/gcc/testsuite/gcc.dg/pr109546.c b/gcc/testsuite/gcc.dg/pr109546.c
new file mode 100644
index 00000000000..ba8af0f31fa
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr109546.c
@@ -0,0 +1,24 @@ 
+/* { dg-do compile } */
+/* { dg-options "-O3 -fdump-tree-optimized" } */
+
+void foo(void);
+static int a, c;
+static int *b = &a;
+static int **d = &b;
+void assert_fail() __attribute__((__noreturn__));
+int main() {
+  int *e = *d;
+  if (e == &a || e == &c);
+  else {
+    __builtin_unreachable();
+  assert_fail();
+  }
+  if (e == &a || e == &c);
+  else
+    foo();
+}
+
+/* { dg-final { scan-tree-dump-not "assert_fail" "optimized" } } */
+/* { dg-final { scan-tree-dump-not "foo" "optimized" } } */
+
+
diff --git a/gcc/tree-vrp.cc b/gcc/tree-vrp.cc
index f4d484526c7..9b870640e23 100644
--- a/gcc/tree-vrp.cc
+++ b/gcc/tree-vrp.cc
@@ -150,7 +150,9 @@  remove_unreachable::remove_and_update_globals (bool final_p)
       // If this is already a constant condition, don't look either
       if (!lhs_p && !rhs_p)
 	continue;
-
+      // Do not remove addresses early. ie if (x == &y)
+      if (!final_p && lhs_p && TREE_CODE (gimple_cond_rhs (s)) == ADDR_EXPR)
+	continue;
       bool dominate_exit_p = true;
       FOR_EACH_GORI_EXPORT_NAME (m_ranger.gori (), e->src, name)
 	{