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(expand_binop): Convert X - C to X + (-C). 

From-SVN: r2278
This commit is contained in:
Richard Kenner 1992-09-29 10:14:19 -04:00
parent 7f11183e26
commit 8aecce0a61
1 changed files with 9 additions and 13 deletions
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22
gcc/optabs.c
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@ -297,6 +297,15 @@ expand_binop (mode, binoptab, op0, op1, target, unsignedp, methods)
op1 = force_not_mem (op1);
}
/* If subtracting an integer constant, convert this into an addition of
the negated constant. */
if (binoptab == sub_optab && GET_CODE (op1) == CONST_INT)
{
op1 = negate_rtx (mode, op1);
binoptab = add_optab;
}
/* If we are inside an appropriately-short loop and one operand is an
expensive constant, force it into a register. */
if (CONSTANT_P (op0) && preserve_subexpressions_p ()
@ -307,19 +316,6 @@ expand_binop (mode, binoptab, op0, op1, target, unsignedp, methods)
&& rtx_cost (op1, binoptab->code) > 2)
op1 = force_reg (shift_op ? word_mode : mode, op1);
#if 0 /* Turned off because it seems to be a kludgy method. */
/* If subtracting integer from pointer, and the pointer has a special mode,
then change it to an add. We use the add insn of Pmode for combining
integers with pointers, and the sub insn to subtract two pointers. */
if (binoptab == sub_optab
&& GET_MODE (op0) == Pmode && GET_MODE (op1) != Pmode)
{
op1 = negate_rtx (GET_MODE(op1), op1);
binoptab = add_optab;
}
#endif /* 0 */
/* Record where to delete back to if we backtrack. */
last = get_last_insn ();