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expr.c (expand_expr): Do not apply distributive law in EXPAND_SUM case.

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* expr.c (expand_expr) [MULT_EXPR]: Do not apply distributive law
        in EXPAND_SUM case.  Use host_integerp/tree_low_cst.

From-SVN: r50033
This commit is contained in:
Richard Henderson 2002-02-25 21:46:15 -08:00 committed by Richard Henderson
parent 1bc59af523
commit 3b40e71b7b
2 changed files with 16 additions and 14 deletions
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5
gcc/ChangeLog
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@ -1,3 +1,8 @@
2002-02-25 Richard Henderson <rth@redhat.com>
* expr.c (expand_expr) [MULT_EXPR]: Do not apply distributive law
in EXPAND_SUM case. Use host_integerp/tree_low_cst.
2002-02-25 Jakub Jelinek <jakub@redhat.com>
PR target/5755

25
gcc/expr.c
View File

@ -7610,23 +7610,20 @@ expand_expr (exp, target, tmode, modifier)
indexed address, for machines that support that. */
if (modifier == EXPAND_SUM && mode == ptr_mode
&& TREE_CODE (TREE_OPERAND (exp, 1)) == INTEGER_CST
&& GET_MODE_BITSIZE (mode) <= HOST_BITS_PER_WIDE_INT)
&& host_integerp (TREE_OPERAND (exp, 1), 0))
{
op0 = expand_expr (TREE_OPERAND (exp, 0), subtarget, VOIDmode,
EXPAND_SUM);
/* Apply distributive law if OP0 is x+c. */
if (GET_CODE (op0) == PLUS
&& GET_CODE (XEXP (op0, 1)) == CONST_INT)
return
gen_rtx_PLUS
(mode,
gen_rtx_MULT
(mode, XEXP (op0, 0),
GEN_INT (TREE_INT_CST_LOW (TREE_OPERAND (exp, 1)))),
GEN_INT (TREE_INT_CST_LOW (TREE_OPERAND (exp, 1))
* INTVAL (XEXP (op0, 1))));
/* If we knew for certain that this is arithmetic for an array
reference, and we knew the bounds of the array, then we could
apply the distributive law across (PLUS X C) for constant C.
Without such knowledge, we risk overflowing the computation
when both X and C are large, but X+C isn't. */
/* ??? Could perhaps special-case EXP being unsigned and C being
positive. In that case we are certain that X+C is no smaller
than X and so the transformed expression will overflow iff the
original would have. */
if (GET_CODE (op0) != REG)
op0 = force_operand (op0, NULL_RTX);
@ -7635,7 +7632,7 @@ expand_expr (exp, target, tmode, modifier)
return
gen_rtx_MULT (mode, op0,
GEN_INT (TREE_INT_CST_LOW (TREE_OPERAND (exp, 1))));
GEN_INT (tree_low_cst (TREE_OPERAND (exp, 1), 0)));
}
if (! safe_from_p (subtarget, TREE_OPERAND (exp, 1), 1))