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[ranger] x == -0.0 does not mean we can replace x with -0.0

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On the true side of x == -0.0, we can't just blindly value propagate
the -0.0 into every use of x because x could be +0.0.

With this change, we only allow the transformation if
!HONOR_SIGNED_ZEROS or if the range is known not to contain 0.

gcc/ChangeLog:

	* range-op-float.cc (foperator_equal::op1_range): Do not blindly
	copy op2 range when honoring signed zeros.
This commit is contained in:
Aldy Hernandez 2022-08-26 16:55:52 +02:00
parent 79db991ece
commit d085901e0e
1 changed files with 15 additions and 2 deletions
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17
gcc/range-op-float.cc
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@ -252,8 +252,21 @@ foperator_equal::op1_range (frange &r, tree type,
switch (get_bool_state (r, lhs, type))
{
case BRS_TRUE:
// If it's true, the result is the same as OP2.
r = op2;
if (HONOR_SIGNED_ZEROS (type)
&& op2.contains_p (build_zero_cst (type)))
{
// With signed zeros, x == -0.0 does not mean we can replace
// x with -0.0, because x may be either +0.0 or -0.0.
r.set_varying (type);
}
else
{
// If it's true, the result is the same as OP2.
//
// If the range does not actually contain zeros, this should
// always be OK.
r = op2;
}
// The TRUE side of op1 == op2 implies op1 is !NAN.
r.set_nan (fp_prop::NO);
break;