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(fold_rtx, case PLUS): When seeing if negative of constant is around, 

make sure not dealing with largest negative.

From-SVN: r13953
This commit is contained in:
Richard Kenner 1997-04-21 16:30:16 -04:00
parent 9ee3c68737
commit 5d595063ff
1 changed files with 10 additions and 4 deletions
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14
gcc/cse.c
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@ -5581,11 +5581,17 @@ fold_rtx (x, insn)
/* If second operand is a register equivalent to a negative
CONST_INT, see if we can find a register equivalent to the
positive constant. Make a MINUS if so. Don't do this for
a negative constant since we might then alternate between
a non-negative constant since we might then alternate between
chosing positive and negative constants. Having the positive
constant previously-used is the more common case. */
if (const_arg1 && GET_CODE (const_arg1) == CONST_INT
&& INTVAL (const_arg1) < 0 && GET_CODE (folded_arg1) == REG)
constant previously-used is the more common case. Be sure
the resulting constant is non-negative; if const_arg1 were
the smallest negative number this would overflow: depending
on the mode, this would either just be the same value (and
hence not save anything) or be incorrect. */
if (const_arg1 != 0 && GET_CODE (const_arg1) == CONST_INT
&& INTVAL (const_arg1) < 0
&& - INTVAL (const_arg1) >= 0
&& GET_CODE (folded_arg1) == REG)
{
rtx new_const = GEN_INT (- INTVAL (const_arg1));
struct table_elt *p