[PATCH] Fix PR 110874: infinite loop in gimple_bitwise_inverted_equal_p with fre

[Andrew Pinski via Gcc-patches]

So I didn't expect valueization to cause calling gimple_nop_convert
to iterate between 2 different SSA names causing an infinite loop
in gimple_bitwise_inverted_equal_p.
So we should cause a bound on gimple_bitwise_inverted_equal_p calling
gimple_nop_convert and only look through one rather than always.

OK? Bootstrapped and tested on x86_64-linux-gnu with no regressions.

gcc/ChangeLog:

        PR tree-optimization/110874
        * gimple-match-head.cc (gimple_bitwise_inverted_equal_p):
        Add new argument, again with default value of true.
        Don't try gimple_nop_convert if again is false.
        Update call to gimple_bitwise_inverted_equal_p for
        new argument.

gcc/testsuite/ChangeLog:

        PR tree-optimization/110874
        * gcc.c-torture/compile/pr110874-a.c: New test.
---
 gcc/gimple-match-head.cc                        | 14 +++++++++-----
 .../gcc.c-torture/compile/pr110874-a.c          | 17 +++++++++++++++++
 2 files changed, 26 insertions(+), 5 deletions(-)
 create mode 100644 gcc/testsuite/gcc.c-torture/compile/pr110874-a.c

diff --git a/gcc/gimple-match-head.cc b/gcc/gimple-match-head.cc
index b1e96304d7c..e91aaab86dd 100644
--- a/gcc/gimple-match-head.cc
+++ b/gcc/gimple-match-head.cc
@@ -273,7 +273,7 @@ gimple_bitwise_equal_p (tree expr1, tree expr2, tree 
(*valueize) (tree))
 /* Helper function for bitwise_equal_p macro.  */
 
 static inline bool
-gimple_bitwise_inverted_equal_p (tree expr1, tree expr2, tree (*valueize) 
(tree))
+gimple_bitwise_inverted_equal_p (tree expr1, tree expr2, tree (*valueize) 
(tree), bool again = true)
 {
   if (expr1 == expr2)
     return false;
@@ -285,12 +285,16 @@ gimple_bitwise_inverted_equal_p (tree expr1, tree expr2, 
tree (*valueize) (tree)
     return false;
 
   tree other;
-  if (gimple_nop_convert (expr1, &other, valueize)
-      && gimple_bitwise_inverted_equal_p (other, expr2, valueize))
+  if (again
+      && gimple_nop_convert (expr1, &other, valueize)
+      && other != expr1
+      && gimple_bitwise_inverted_equal_p (other, expr2, valueize, false))
     return true;
 
-  if (gimple_nop_convert (expr2, &other, valueize)
-      && gimple_bitwise_inverted_equal_p (expr1, other, valueize))
+  if (again
+      && gimple_nop_convert (expr2, &other, valueize)
+      && other != expr2
+      && gimple_bitwise_inverted_equal_p (expr1, other, valueize, false))
     return true;
 
   if (TREE_CODE (expr1) != SSA_NAME
diff --git a/gcc/testsuite/gcc.c-torture/compile/pr110874-a.c 
b/gcc/testsuite/gcc.c-torture/compile/pr110874-a.c
new file mode 100644
index 00000000000..b314410a892
--- /dev/null
+++ b/gcc/testsuite/gcc.c-torture/compile/pr110874-a.c
@@ -0,0 +1,17 @@
+struct S1 {
+  unsigned f0;
+};
+static int g_161;
+void func_109(unsigned g_227, unsigned t) {
+  struct S1 l_178;
+  int l_160 = 0x1FAE99D5L;
+  int *l_230[] = {&l_160};
+  if (l_160) {
+    for (l_178.f0 = -7; l_178.f0;) {
+      ++g_227;
+      break;
+    }
+    (g_161) = g_227;
+  }
+  (g_161) &= t;
+}
-- 
2.31.1