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fold-const.c (fold): Transform (c1 - x) cmp c2...

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* fold-const.c (fold):  Transform (c1 - x) cmp c2, where cmp is a
	comparison operation and c1/c2 are floating point constants into
	x swap(cmp) (c1 - c2).

	* gcc.dg/20030414-2.c: New test case.

From-SVN: r65584
This commit is contained in:
Roger Sayle 2003-04-14 20:16:58 +00:00 committed by Roger Sayle
parent 22fc0e9ffe
commit 15d4fd9863
4 changed files with 62 additions and 1 deletions
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8
gcc/ChangeLog
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@ -1,3 +1,9 @@
2003-04-14 Roger Sayle <roger@eyesopen.com>
* fold-const.c (fold): Transform (c1 - x) cmp c2, where cmp is a
comparison operation and c1/c2 are floating point constants into
x swap(cmp) (c1 - c2).
2003-04-14 Vladimir Makarov <vmakarov@redhat.com>
* genautomata.c (output_translate_vect): Fix a typo in loop
@ -1376,7 +1382,7 @@ Thu Apr 3 00:18:49 CEST 2003 Jan Hubicka <jh@suse.cz>
2003-04-01 Roger Sayle <roger@eyesopen.com>
PR fortran/9974
* gcse.c (reg_killed_on_egde): New function to test whether the
* gcse.c (reg_killed_on_edge): New function to test whether the
given reg is overwritten by any instruction queued on an edge.
(bypass_block): Ignore substitutions killed on incoming edges.
Don't bypass outgoing edges that have queued instructions.

13
gcc/fold-const.c
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@ -6484,6 +6484,19 @@ fold (expr)
&& ! TREE_CONSTANT_OVERFLOW (tem))
return fold (build (code, type, TREE_OPERAND (arg0, 0), tem));
/* Likewise, we can simplify a comparison of a real constant with
a MINUS_EXPR whose first operand is also a real constant, i.e.
(c1 - x) < c2 becomes x > c1-c2. */
if (flag_unsafe_math_optimizations
&& TREE_CODE (arg1) == REAL_CST
&& TREE_CODE (arg0) == MINUS_EXPR
&& TREE_CODE (TREE_OPERAND (arg0, 0)) == REAL_CST
&& 0 != (tem = const_binop (MINUS_EXPR, TREE_OPERAND (arg0, 0),
arg1, 0))
&& ! TREE_CONSTANT_OVERFLOW (tem))
return fold (build (swap_tree_comparison (code), type,
TREE_OPERAND (arg0, 1), tem));
/* Fold comparisons against built-in math functions. */
if (TREE_CODE (arg1) == REAL_CST
&& flag_unsafe_math_optimizations

4
gcc/testsuite/ChangeLog
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@ -1,3 +1,7 @@
2003-04-14 Roger Sayle <roger@eyesopen.com>
* gcc.dg/20030414-2.c: New test case.
2003-04-14 Hans-Peter Nilsson <hp@axis.com>
PR target/10377

38
gcc/testsuite/gcc.dg/20030414-2.c Normal file
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@ -0,0 +1,38 @@
/* Copyright (C) 2003 Free Software Foundation.
Check that constant folding (c1 - x) op c2 into x swap(op) c1-c2
doesn't break anything.
Written by Roger Sayle, 27th March 2003. */
/* { dg-do run } */
/* { dg-options "-O2 -ffast-math" } */
extern void abort (void);
int foo(double x)
{
return (10.0 - x) > 3.0;
}
int bar (double x)
{
return (10.0 - x) == 5.0;
}
int main()
{
if (foo (8.0))
abort ();
if (! foo (6.0))
abort ();
if (bar (1.0))
abort ();
if (! bar (5.0))
abort ();
return 0;
}