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fold-const.c (extract_muldiv, [...]): Reverse operation if C is negative. 

* fold-const.c (extract_muldiv, case {MIN,MAX}_EXPR): Reverse
	operation if C is negative.
	(extract_muldiv, case SAVE_EXPR): Supresss if arg has side effects.
	(extract_muldiv, case {PLUS,MINUS}_EXPR): Don't apply distributive
	law for some divisions if constant is negative and change other
	divisions to the opposite rounding.

From-SVN: r30714
This commit is contained in:
Richard Kenner 1999-11-29 22:56:39 +00:00 committed by Richard Kenner
parent ce64861eed
commit 59adecfa8c
2 changed files with 54 additions and 19 deletions
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7
gcc/ChangeLog
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@ -1,5 +1,12 @@
Mon Nov 29 16:56:42 1999 Richard Kenner <kenner@vlsi1.ultra.nyu.edu>
* fold-const.c (extract_muldiv, case {MIN,MAX}_EXPR): Reverse
operation if C is negative.
(extract_muldiv, case SAVE_EXPR): Supresss if arg has side effects.
(extract_muldiv, case {PLUS,MINUS}_EXPR): Don't apply distributive
law for some divisions if constant is negative and change other
divisions to the opposite rounding.
* expr.c (store_constructor_field): If bit position is not multiple
of alignment of TARGET's mode, use BLKmode.

66
gcc/fold-const.c
View File

@ -4299,8 +4299,8 @@ extract_muldiv (t, c, code, wide_type)
case CONVERT_EXPR: case NON_LVALUE_EXPR: case NOP_EXPR:
/* Pass the constant down and see if we can make a simplification. If
we can, replace this expression with a conversion of that result to
our type. */
we can, replace this expression with the inner simplification for
possible later conversion to our or some other type. */
if (0 != (t1 = extract_muldiv (op0, convert (TREE_TYPE (op0), c), code,
code == MULT_EXPR ? ctype : NULL_TREE)))
return t1;
@ -4315,8 +4315,13 @@ extract_muldiv (t, c, code, wide_type)
/* MIN (a, b) / 5 -> MIN (a / 5, b / 5) */
if ((t1 = extract_muldiv (op0, c, code, wide_type)) != 0
&& (t2 = extract_muldiv (op1, c, code, wide_type)) != 0)
return fold (build (tcode, ctype, convert (ctype, t1),
convert (ctype, t2)));
{
if (tree_int_cst_sgn (c) < 0)
tcode = (tcode == MIN_EXPR ? MAX_EXPR : MIN_EXPR);
return fold (build (tcode, ctype, convert (ctype, t1),
convert (ctype, t2)));
}
break;
case WITH_RECORD_EXPR:
@ -4326,9 +4331,12 @@ extract_muldiv (t, c, code, wide_type)
break;
case SAVE_EXPR:
/* If this has not been evaluated, we can see if we can do
something inside it and make a new one. */
if (SAVE_EXPR_RTL (t) == 0
/* If this has not been evaluated and the operand has no side effects,
we can see if we can do something inside it and make a new one.
Note that this test is overly conservative since we can do this
if the only reason it had side effects is that it was another
similar SAVE_EXPR, but that isn't worth bothering with. */
if (SAVE_EXPR_RTL (t) == 0 && ! TREE_SIDE_EFFECTS (TREE_OPERAND (t, 0))
&& 0 != (t1 = extract_muldiv (TREE_OPERAND (t, 0), c, code,
wide_type)))
return save_expr (t1);
@ -4362,26 +4370,46 @@ extract_muldiv (t, c, code, wide_type)
else if (TREE_CODE (op1) != INTEGER_CST)
break;
/* If this was a subtraction, negate OP1 and set it to be an addition.
This simplifies the logic below. */
if (tcode == MINUS_EXPR)
tcode = PLUS_EXPR, op1 = negate_expr (op1);
/* If either OP1 or C are negative, this optimization is not safe for
some of the division and remainder types while for others we need
to change the code. */
if (tree_int_cst_sgn (op1) < 0 || tree_int_cst_sgn (c) < 0)
{
if (code == CEIL_DIV_EXPR)
code = FLOOR_DIV_EXPR;
else if (code == CEIL_MOD_EXPR)
code = FLOOR_MOD_EXPR;
else if (code == FLOOR_DIV_EXPR)
code = CEIL_DIV_EXPR;
else if (code == FLOOR_MOD_EXPR)
code = CEIL_MOD_EXPR;
else if (code != MULT_EXPR)
break;
}
/* Now do the operation and verify it doesn't overflow. */
op1 = const_binop (code, convert (ctype, op1), convert (ctype, c), 0);
if (op1 == 0 || TREE_OVERFLOW (op1))
break;
/* If we were able to eliminate our operation from the first side,
apply our operation to the second side and reform the PLUS or
MINUS. */
if (t1 != 0 && (TREE_CODE (t1) != code || code == MULT_EXPR)
&& 0 != (t2 = const_binop (code, convert (ctype, op1),
convert (ctype, c), 0))
&& ! TREE_OVERFLOW (t2))
return fold (build (tcode, ctype, convert (ctype, t1), t2));
apply our operation to the second side and reform the PLUS. */
if (t1 != 0 && (TREE_CODE (t1) != code || code == MULT_EXPR))
return fold (build (tcode, ctype, convert (ctype, t1), op1));
/* The last case is if we are a multiply. In that case, we can
apply the distributive law to commute the multiply and addition
if the multiplication of the constants doesn't overflow. */
if (code == MULT_EXPR
&& 0 != (t1 = const_binop (code, convert (ctype, op1),
convert (ctype, c), 0))
&& ! TREE_OVERFLOW (t1))
if (code == MULT_EXPR)
return fold (build (tcode, ctype, fold (build (code, ctype,
convert (ctype, op0),
convert (ctype, c))),
t1));
op1));
break;