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fold-const.c (fold): Reassociate (+ (+ (* a b) c) (* d e)) as (+ (+ (* a b) (* d e)) c).

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* fold-const.c (fold): Reassociate (+ (+ (* a b) c) (* d e))
        as (+ (+ (* a b) (* d e)) c).  Factor a common power-of-two
        multiplicand out of (+ (* a b) (* c d)).

From-SVN: r28829
This commit is contained in:
Richard Henderson 1999-08-24 15:37:34 -07:00 • committed by Richard Henderson
parent f2a1bc0267
commit abe4f192b7
2 changed files with 67 additions and 0 deletions
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6
gcc/ChangeLog
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@ -1,3 +1,9 @@
Tue Aug 24 15:37:03 1999 Richard Henderson <rth@cygnus.com>
* fold-const.c (fold): Reassociate (+ (+ (* a b) c) (* d e))
as (+ (+ (* a b) (* d e)) c). Factor a common power-of-two
multiplicand out of (+ (* a b) (* c d)).
Tue Aug 24 11:46:10 1999 Bob Manson <manson@cygnus.com>
Richard Henderson <rth@cygnus.com>

61
gcc/fold-const.c
View file

@ -4757,6 +4757,37 @@ fold (expr)
goto bit_ior;
}
/* Reassociate (plus (plus (mult) (foo)) (mult)) as
(plus (plus (mult) (mult)) (foo)) so that we can
take advantage of the factoring cases below. */
if ((TREE_CODE (arg0) == PLUS_EXPR
&& TREE_CODE (arg1) == MULT_EXPR)
|| (TREE_CODE (arg1) == PLUS_EXPR
&& TREE_CODE (arg0) == MULT_EXPR))
{
tree parg0, parg1, parg, marg;
if (TREE_CODE (arg0) == PLUS_EXPR)
parg = arg0, marg = arg1;
else
parg = arg1, marg = arg0;
parg0 = TREE_OPERAND (parg, 0);
parg1 = TREE_OPERAND (parg, 1);
STRIP_NOPS (parg0);
STRIP_NOPS (parg1);
if (TREE_CODE (parg0) == MULT_EXPR
&& TREE_CODE (parg1) != MULT_EXPR)
return fold (build (PLUS_EXPR, type,
fold (build (PLUS_EXPR, type, parg0, marg)),
parg1));
if (TREE_CODE (parg0) != MULT_EXPR
&& TREE_CODE (parg1) == MULT_EXPR)
return fold (build (PLUS_EXPR, type,
fold (build (PLUS_EXPR, type, parg1, marg)),
parg0));
}
if (TREE_CODE (arg0) == MULT_EXPR && TREE_CODE (arg1) == MULT_EXPR)
{
tree arg00, arg01, arg10, arg11;
@ -4782,6 +4813,36 @@ fold (expr)
else if (operand_equal_p (arg01, arg10, 0))
same = arg01, alt0 = arg00, alt1 = arg11;
/* No identical multiplicands; see if we can find a common
power-of-two factor in non-power-of-two multiplies. This
can help in multi-dimensional array access. */
else if (TREE_CODE (arg01) == INTEGER_CST
&& TREE_CODE (arg11) == INTEGER_CST
&& TREE_INT_CST_HIGH (arg01) == 0
&& TREE_INT_CST_HIGH (arg11) == 0)
{
HOST_WIDE_INT int01, int11, tmp;
int01 = TREE_INT_CST_LOW (arg01);
int11 = TREE_INT_CST_LOW (arg11);
/* Move min of absolute values to int11. */
if ((int01 >= 0 ? int01 : -int01)
< (int11 >= 0 ? int11 : -int11))
{
tmp = int01, int01 = int11, int11 = tmp;
alt0 = arg00, arg00 = arg10, arg10 = alt0;
alt0 = arg01, arg01 = arg11, arg11 = alt0;
}
if (exact_log2 (int11) > 0 && int01 % int11 == 0)
{
alt0 = fold (build (MULT_EXPR, type, arg00,
build_int_2 (int01 / int11, 0)));
alt1 = arg10;
same = arg11;
}
}
if (same)
return fold (build (MULT_EXPR, type,
fold (build (PLUS_EXPR, type, alt0, alt1)),