Fix tree-optimization/103314 : Limit folding of (type) X op CST where type is a nop...

There is some re-association code in fold_binary which conflicts with
this optimization due keeping around some "constants" which are not
INTEGER_CST (1 << -1) so we end up in an infinite loop because of that.
So we need to limit this case to GIMPLE level only.

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

	PR tree-optimization/103314

gcc/ChangeLog:

	* match.pd ((type) X op CST): Restrict the equal
	TYPE_PRECISION case to GIMPLE only.

gcc/testsuite/ChangeLog:

	* gcc.c-torture/compile/pr103314-1.c: New test.

diff --git a/gcc/match.pd b/gcc/match.pd
index 4042b535b857373aab08cdb32774fe4422bf2caa..e5985defe6f7e326dc18610a5f719d41f7063608 100644 (file)
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -1619,7 +1619,11 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
              after hoisting the conversion the operation will be narrower.
              It is also a good if the conversion is a nop as moves the
              conversion to one side; allowing for combining of the conversions.  */
-          TYPE_PRECISION (TREE_TYPE (@0)) <= TYPE_PRECISION (type)
+          TYPE_PRECISION (TREE_TYPE (@0)) < TYPE_PRECISION (type)
+          /* The conversion check for being a nop can only be done at the gimple
+             level as fold_binary has some re-association code which can conflict
+             with this if there is a "constant" which is not a full INTEGER_CST.  */
+          || (GIMPLE && TYPE_PRECISION (TREE_TYPE (@0)) == TYPE_PRECISION (type))
           /* It's also a good idea if the conversion is to a non-integer
              mode.  */
           || GET_MODE_CLASS (TYPE_MODE (type)) != MODE_INT

diff --git a/gcc/testsuite/gcc.c-torture/compile/pr103314-1.c b/gcc/testsuite/gcc.c-torture/compile/pr103314-1.c
new file mode 100644 (file)
index 0000000..f4a6313
--- /dev/null
+++ b/gcc/testsuite/gcc.c-torture/compile/pr103314-1.c
@@ -0,0 +1,6 @@
+/* { dg-options "" } */
+int main() {
+  int t = 1;
+  unsigned c = 0, d1 = t ? 1 ^ c ^ 1 >> (-1) : 0; /* { dg-warning "is negative"  } */
+  return d1;
+}