[gcc r12-5400] Fix tree-optimization/103314 : Limit folding of (type) X op CST where type is a nop convert to gimpl

[gcc r12-5400] Fix tree-optimization/103314 : Limit folding of (type) X op CST where type is a nop convert to gimpl

[Andrew Pinski]

https://gcc.gnu.org/g:ea2954df43d4162af23a20c84f4c5485463977ac

commit r12-5400-gea2954df43d4162af23a20c84f4c5485463977ac
Author: Andrew Pinski <apinski@marvell.com>
Date:   Fri Nov 19 01:42:41 2021 +0000

    Fix tree-optimization/103314 : Limit folding of (type) X op CST where type is a nop convert to gimple
    
    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:
---
 gcc/match.pd                                     | 6 +++++-
 gcc/testsuite/gcc.c-torture/compile/pr103314-1.c | 6 ++++++
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/gcc/match.pd b/gcc/match.pd
index 4042b535b85..e5985defe6f 100644
--- 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
index 00000000000..f4a63130421
--- /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;
+}