Hello,
this patch only handles the simple case where the constant is 0, I'll keep
the PR open for the more general case. Note that if we split
flag_trapping_math into no|weak|strict, the test here would be !=strict,
since we only remove trapping operations.
Passes bootstrap+testsuite on x86_64-linux-gnu.
2013-05-27 Marc Glisse <marc.gli...@inria.fr>
PR tree-optimization/57371
gcc/
* fold-const.c (fold_comparison): Fold comparison of a FLOAT_EXPR
with 0.
gcc/testsuite/
* gcc.dg/pr57371-1.c: New testcase.
* gcc.dg/pr57371-2.c: Likewise.
* gcc.dg/pr57371-3.c: Likewise.
--
Marc GlisseIndex: fold-const.c
===================================================================
--- fold-const.c (revision 199323)
+++ fold-const.c (working copy)
@@ -9362,20 +9362,38 @@ fold_comparison (location_t loc, enum tr
}
/* Fold comparisons against infinity. */
if (REAL_VALUE_ISINF (cst)
&& MODE_HAS_INFINITIES (TYPE_MODE (TREE_TYPE (arg1))))
{
tem = fold_inf_compare (loc, code, type, arg0, arg1);
if (tem != NULL_TREE)
return tem;
}
+
+ /* (double)i CMP 0 is just i CMP 0. See PR 57371 for how this
+ can be extended to non-zero constants. */
+ if (TREE_CODE (arg0) == FLOAT_EXPR && real_zerop (arg1))
+ {
+ tree inner = TREE_OPERAND (arg0, 0);
+ tree itype = TREE_TYPE (inner);
+ tree ftype = TREE_TYPE (arg0);
+ /* If ftype cannot represent exactly all values of itype,
+ we may have an inexact exception. If the conversion from
+ itype to ftype may overflow (unsigned __int128 to float),
+ we may have an overflow exception. */
+ if (!flag_trapping_math
+ || (unsigned) significand_size (TYPE_MODE (ftype))
+ >= element_precision (itype) - !TYPE_UNSIGNED (itype))
+ return fold_build2_loc (loc, code, type, inner,
+ build_zero_cst (itype));
+ }
}
/* If this is a comparison of a real constant with a PLUS_EXPR
or a MINUS_EXPR of a real constant, we can convert it into a
comparison with a revised real constant as long as no overflow
occurs when unsafe_math_optimizations are enabled. */
if (flag_unsafe_math_optimizations
&& TREE_CODE (arg1) == REAL_CST
&& (TREE_CODE (arg0) == PLUS_EXPR
|| TREE_CODE (arg0) == MINUS_EXPR)
Index: testsuite/gcc.dg/pr57371-3.c
===================================================================
--- testsuite/gcc.dg/pr57371-3.c (revision 0)
+++ testsuite/gcc.dg/pr57371-3.c (revision 0)
@@ -0,0 +1,11 @@
+/* { dg-do compile } */
+/* { dg-options "-O -fdump-tree-optimized -ftrapping-math" } */
+
+int f (unsigned long long x)
+{
+ float y = x;
+ return y <= 0;
+}
+
+/* { dg-final { scan-tree-dump "float" "optimized" } } */
+/* { dg-final { cleanup-tree-dump "optimized" } } */
Property changes on: testsuite/gcc.dg/pr57371-3.c
___________________________________________________________________
Added: svn:keywords
+ Author Date Id Revision URL
Added: svn:eol-style
+ native
Index: testsuite/gcc.dg/pr57371-1.c
===================================================================
--- testsuite/gcc.dg/pr57371-1.c (revision 0)
+++ testsuite/gcc.dg/pr57371-1.c (revision 0)
@@ -0,0 +1,11 @@
+/* { dg-do compile } */
+/* { dg-options "-O -fdump-tree-optimized -ftrapping-math" } */
+
+int f (char x)
+{
+ long double y = x;
+ return y <= 0;
+}
+
+/* { dg-final { scan-tree-dump-not "double" "optimized" } } */
+/* { dg-final { cleanup-tree-dump "optimized" } } */
Property changes on: testsuite/gcc.dg/pr57371-1.c
___________________________________________________________________
Added: svn:keywords
+ Author Date Id Revision URL
Added: svn:eol-style
+ native
Index: testsuite/gcc.dg/pr57371-2.c
===================================================================
--- testsuite/gcc.dg/pr57371-2.c (revision 0)
+++ testsuite/gcc.dg/pr57371-2.c (revision 0)
@@ -0,0 +1,11 @@
+/* { dg-do compile } */
+/* { dg-options "-O -fdump-tree-optimized -fno-trapping-math" } */
+
+int f (unsigned long long x)
+{
+ float y = x;
+ return y <= 0;
+}
+
+/* { dg-final { scan-tree-dump-not "float" "optimized" } } */
+/* { dg-final { cleanup-tree-dump "optimized" } } */
Property changes on: testsuite/gcc.dg/pr57371-2.c
___________________________________________________________________
Added: svn:eol-style
+ native
Added: svn:keywords
+ Author Date Id Revision URL
