PATCH] Fix PR 31531: A microoptimization of isnegative of signed integer

[Hurugalawadi, Naveen]

Hi,

Please find attached the patch that performs optimization on unsigned values.

Original fold-const part implemented in match.pd.

Please review the patch and let us know if it's OK?

Regression Tested on X86_64 with no regressions.

Thanks,
Naveen

ChangeLog:
* match.pd (cmp (convert (bit_not @0)) INTEGER_CST@1): New Simplifier.

Testsuite/ChangeLog:
* gcc.dg/pr31531.c : New testcase.
diff --git a/gcc/match.pd b/gcc/match.pd
index 6c8ebd5..42f772b 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -1452,6 +1452,17 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
        && (TYPE_SIZE (TREE_TYPE (@0)) == TYPE_SIZE (TREE_TYPE (@1))))
    (view_convert @1)))
 
+/* Fold ((CAST)~X) op C as ((CAST)X) op' ~C, where op' is the
+   swapped comparison.  */
+(for cmp (tcc_comparison)
+     scmp (swapped_tcc_comparison)
+ (simplify
+  (cmp (convert (bit_not @0)) INTEGER_CST@1)
+  (if (TYPE_PRECISION (type) == TYPE_PRECISION (TREE_TYPE (@0))
+       && TYPE_PRECISION (TREE_TYPE (@0)) == TYPE_PRECISION (TREE_TYPE (@1)))
+   (with { tree cst = fold_convert (TREE_TYPE (@0), @1); }
+    (scmp @0 (bit_not { cst; }))))))
+
 /* Re-association barriers around constants and other re-association
    barriers can be removed.  */
 (simplify
diff --git a/gcc/testsuite/gcc.dg/pr31531.c b/gcc/testsuite/gcc.dg/pr31531.c
new file mode 100644
index 0000000..d687c91
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr31531.c
@@ -0,0 +1,12 @@
+/* { dg-do compile } */
+/* { dg-options "-fdump-tree-gimple" } */
+int isnegative_optimized_4 (unsigned int X)
+{
+  int result;
+  if ((~X) >> 31)
+    result = 0;
+  else
+    result = 1;
+  return result;
+}
+/* { dg-final { scan-tree-dump-times "0 != 0" 1 "gimple" } } */