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re PR rtl-optimization/28634 (rounding problem with -fdelayed-branch on hppa/mips)

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gcc/
	PR rtl-optimization/28634
	* reorg.c (fill_slots_from_thread): Do not assume A + X - X == A
	for floating-point modes unless flag_unsafe_math_optimizations.

gcc/testsuite/
	PR rtl-optimization/28634
	* gcc.c-torture/execute/ieee/pr28634.c: New test.

From-SVN: r116124
This commit is contained in:
Richard Sandiford 2006-08-14 11:55:52 +00:00 committed by Richard Sandiford
parent 62eed976f5
commit 2b3969faee
4 changed files with 28 additions and 0 deletions
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6
gcc/ChangeLog
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@ -1,3 +1,9 @@
2006-08-14 Richard Sandiford <richard@codesourcery.com>
PR rtl-optimization/28634
* reorg.c (fill_slots_from_thread): Do not assume A + X - X == A
for floating-point modes unless flag_unsafe_math_optimizations.
2006-08-13 Alexandre Oliva <aoliva@redhat.com>
Andrew Pinski <pinskia@physics.uc.edu>

2
gcc/reorg.c
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@ -2817,6 +2817,8 @@ fill_slots_from_thread (rtx insn, rtx condition, rtx thread,
dest = SET_DEST (pat), src = SET_SRC (pat);
if ((GET_CODE (src) == PLUS || GET_CODE (src) == MINUS)
&& rtx_equal_p (XEXP (src, 0), dest)
&& (!FLOAT_MODE_P (GET_MODE (src))
|| flag_unsafe_math_optimizations)
&& ! reg_overlap_mentioned_p (dest, XEXP (src, 1))
&& ! side_effects_p (pat))
{

5
gcc/testsuite/ChangeLog
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@ -1,3 +1,8 @@
2006-08-14 Richard Sandiford <richard@codesourcery.com>
PR rtl-optimization/28634
* gcc.c-torture/execute/ieee/pr28634.c: New test.
2006-08-13 Alexandre Oliva <aoliva@redhat.com>
PR c/27184

15
gcc/testsuite/gcc.c-torture/execute/ieee/pr28634.c Normal file
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@ -0,0 +1,15 @@
/* PR rtl-optimization/28634. On targets with delayed branches,
dbr_schedule could do the next iteration's addition in the
branch delay slot, then subtract the value again if the branch
wasn't taken. This can lead to rounding errors. */
double x = -0x1.0p53;
double y = 1;
int
main (void)
{
while (y > 0)
y += x;
if (y != x + 1)
abort ();
exit (0);
}