[PATCH] Fix ldist memset discovery with -0.0 (PR tree-optimization/72824)
Jakub Jelinek
jakub@redhat.com
Mon Aug 8 18:57:00 GMT 2016
Hi!
Only +0.0 stores can be optimized into memset, -0.0 can't, so if we are
honoring signed zeros, we should make sure the constant is positive.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
2016-08-08 Jakub Jelinek <jakub@redhat.com>
PR tree-optimization/72824
* tree-loop-distribution.c (const_with_all_bytes_same): If honoring
signed zeros, verify real_zerop is not negative.
* gcc.c-torture/execute/ieee/pr72824.c: New test.
--- gcc/tree-loop-distribution.c.jj 2016-07-16 10:41:04.000000000 +0200
+++ gcc/tree-loop-distribution.c 2016-08-07 13:55:19.704681784 +0200
@@ -750,12 +750,40 @@ const_with_all_bytes_same (tree val)
int i, len;
if (integer_zerop (val)
- || real_zerop (val)
|| (TREE_CODE (val) == CONSTRUCTOR
&& !TREE_CLOBBER_P (val)
&& CONSTRUCTOR_NELTS (val) == 0))
return 0;
+ if (real_zerop (val))
+ {
+ if (!HONOR_SIGNED_ZEROS (val))
+ return 0;
+ /* If honoring signed zeros, only return 0 for +0.0, not for -0.0. */
+ switch (TREE_CODE (val))
+ {
+ case REAL_CST:
+ if (!real_isneg (TREE_REAL_CST_PTR (val)))
+ return 0;
+ break;
+ case COMPLEX_CST:
+ if (!const_with_all_bytes_same (TREE_REALPART (val))
+ && !const_with_all_bytes_same (TREE_IMAGPART (val)))
+ return 0;
+ break;
+ case VECTOR_CST:
+ unsigned int j;
+ for (j = 0; j < VECTOR_CST_NELTS (val); ++j)
+ if (const_with_all_bytes_same (val))
+ break;
+ if (j == VECTOR_CST_NELTS (val))
+ return 0;
+ break;
+ default:
+ break;
+ }
+ }
+
if (CHAR_BIT != 8 || BITS_PER_UNIT != 8)
return -1;
--- gcc/testsuite/gcc.c-torture/execute/ieee/pr72824.c.jj 2016-08-07 13:19:42.443863775 +0200
+++ gcc/testsuite/gcc.c-torture/execute/ieee/pr72824.c 2016-08-07 13:19:35.034958218 +0200
@@ -0,0 +1,19 @@
+/* PR tree-optimization/72824 */
+
+static inline void
+foo (float *x, float value)
+{
+ int i;
+ for (i = 0; i < 32; ++i)
+ x[i] = value;
+}
+
+int
+main ()
+{
+ float x[32];
+ foo (x, -0.f);
+ if (__builtin_copysignf (1.0, x[3]) != -1.0f)
+ __builtin_abort ();
+ return 0;
+}
Jakub
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