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re PR tree-optimization/31169 (Bootstrap comparison error at revision 122821)

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PR tree-optimization/31169 
        * tree-vrp.c (extract_range_from_binary_expr) <RSHIFT_EXPR>: Drop
        to varying if the range is outside [0,  prec-1].

From-SVN: r123405
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Richard Henderson 2007-04-01 11:17:38 -07:00 committed by Richard Henderson
parent a616b1da79
commit af33044f05
2 changed files with 24 additions and 11 deletions
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6
gcc/ChangeLog
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@ -1,3 +1,9 @@
2007-04-01 Richard Henderson <rth@redhat.com>
PR tree-optimization/31169
* tree-vrp.c (extract_range_from_binary_expr) <RSHIFT_EXPR>: Drop
to varying if the range is outside [0, prec-1].
2007-04-01 Richard Sandiford <richard@codesourcery.com>
PR target/31388

23
gcc/tree-vrp.c
View File

@ -1813,16 +1813,24 @@ extract_range_from_binary_expr (value_range_t *vr, tree expr)
return;
}
/* If we have a RSHIFT_EXPR with a possibly negative shift
count or an anti-range shift count drop to VR_VARYING.
We currently cannot handle the overflow cases correctly. */
if (code == RSHIFT_EXPR
&& (vr1.type == VR_ANTI_RANGE
|| !vrp_expr_computes_nonnegative (op1, &sop)))
/* If we have a RSHIFT_EXPR with any shift values outside [0..prec-1],
then drop to VR_VARYING. Outside of this range we get undefined
behaviour from the shift operation. We cannot even trust
SHIFT_COUNT_TRUNCATED at this stage, because that applies to rtl
shifts, and the operation at the tree level may be widened. */
if (code == RSHIFT_EXPR)
{
if (vr1.type == VR_ANTI_RANGE
|| !vrp_expr_computes_nonnegative (op1, &sop)
|| (operand_less_p
(build_int_cst (TREE_TYPE (vr1.max),
TYPE_PRECISION (TREE_TYPE (expr)) - 1),
vr1.max) != 0))
{
set_value_range_to_varying (vr);
return;
}
}
/* Multiplications and divisions are a bit tricky to handle,
depending on the mix of signs we have in the two ranges, we
@ -1838,8 +1846,7 @@ extract_range_from_binary_expr (value_range_t *vr, tree expr)
the new range. */
/* Divisions by zero result in a VARYING value. */
if ((code != MULT_EXPR
&& code != RSHIFT_EXPR)
else if (code != MULT_EXPR
&& (vr0.type == VR_ANTI_RANGE || range_includes_zero_p (&vr1)))
{
set_value_range_to_varying (vr);