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fold-const.c (split_tree): Add MINUS_LITP parameter; separate added literals from substracted literals.

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* fold-const.c (split_tree): Add MINUS_LITP parameter; separate
        added literals from substracted literals.
        (associate_trees): Don't convert MINUS_EXPR into PLUS_EXPR.
        (fold) [associate]: Preserve MINUS_EXPR if needed.

	* gcc.c-torture/execute/20020423-1.c: New.

From-SVN: r52695
This commit is contained in:
Eric Botcazou 2002-04-23 16:31:07 -07:00 • committed by Richard Henderson
parent 952bca8474
commit cff2779594
3 changed files with 122 additions and 32 deletions
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24
gcc/ChangeLog
View file

@ -1,3 +1,11 @@
2002-04-23 Eric Botcazou <ebotcazou@multimania.com>
PR c/5430
* fold-const.c (split_tree): Add MINUS_LITP parameter; separate
added literals from substracted literals.
(associate_trees): Don't convert MINUS_EXPR into PLUS_EXPR.
(fold) [associate]: Preserve MINUS_EXPR if needed.
2002-04-23 Zack Weinberg <zack@codesourcery.com>
* doc/install.texi: Clarify which versions of alpha*-dec-osf*
@ -35,9 +43,9 @@ Tue Apr 23 14:24:25 CEST 2002 Jan Hubicka <jh@suse.cz>
2002-04-23 Aldy Hernandez <aldyh@redhat.com>
* config/rs6000/altivec.h (vec_step): Remove extraneous
parentheses.
(vec_ctu): Cast return.
* config/rs6000/altivec.h (vec_step): Remove extraneous
parentheses.
(vec_ctu): Cast return.
2002-04-23 Alan Modra <amodra@bigpond.net.au>
@ -69,11 +77,11 @@ Tue Apr 23 14:24:25 CEST 2002 Jan Hubicka <jh@suse.cz>
2002-04-22 Aldy Hernandez <aldyh@redhat.com>
* config/rs6000/rs6000.md ("*movv4si_internal"): Change 'm'
constraint to 'o' for m=r and r=m alternatives.
("*movv8hi_internal1"): Same.
("*movv16qi_internal1"): Same.
("*movv4sf_internal1"): Same.
* config/rs6000/rs6000.md ("*movv4si_internal"): Change 'm'
constraint to 'o' for m=r and r=m alternatives.
("*movv8hi_internal1"): Same.
("*movv16qi_internal1"): Same.
("*movv4sf_internal1"): Same.
2002-04-22 Janis Johnson <janis187@us.ibm.com>

97
gcc/fold-const.c
View file

@ -62,7 +62,7 @@ static void decode PARAMS ((HOST_WIDE_INT *,
HOST_WIDE_INT *));
static tree negate_expr PARAMS ((tree));
static tree split_tree PARAMS ((tree, enum tree_code, tree *, tree *,
int));
tree *, int));
static tree associate_trees PARAMS ((tree, tree, enum tree_code, tree));
static tree int_const_binop PARAMS ((enum tree_code, tree, tree, int));
static tree const_binop PARAMS ((enum tree_code, tree, tree, int));
@ -876,13 +876,16 @@ negate_expr (t)
combined with CODE to make IN. "constant" means an expression with
TREE_CONSTANT but that isn't an actual constant. CODE must be a
commutative arithmetic operation. Store the constant part into *CONP,
the literal in &LITP and return the variable part. If a part isn't
the literal in *LITP and return the variable part. If a part isn't
present, set it to null. If the tree does not decompose in this way,
return the entire tree as the variable part and the other parts as null.
If CODE is PLUS_EXPR we also split trees that use MINUS_EXPR. In that
case, we negate an operand that was subtracted. If NEGATE_P is true, we
are negating all of IN.
case, we negate an operand that was subtracted. Except if it is a
literal for which we use *MINUS_LITP instead.
If NEGATE_P is true, we are negating all of IN, again except a literal
for which we use *MINUS_LITP instead.
If IN is itself a literal or constant, return it as appropriate.
@ -890,16 +893,17 @@ negate_expr (t)
same type as IN, but they will have the same signedness and mode. */
static tree
split_tree (in, code, conp, litp, negate_p)
split_tree (in, code, conp, litp, minus_litp, negate_p)
tree in;
enum tree_code code;
tree *conp, *litp;
tree *conp, *litp, *minus_litp;
int negate_p;
{
tree var = 0;
*conp = 0;
*litp = 0;
*minus_litp = 0;
/* Strip any conversions that don't change the machine mode or signedness. */
STRIP_SIGN_NOPS (in);
@ -941,9 +945,12 @@ split_tree (in, code, conp, litp, negate_p)
var = op1, neg_var_p = neg1_p;
/* Now do any needed negations. */
if (neg_litp_p) *litp = negate_expr (*litp);
if (neg_conp_p) *conp = negate_expr (*conp);
if (neg_var_p) var = negate_expr (var);
if (neg_litp_p)
*minus_litp = *litp, *litp = 0;
if (neg_conp_p)
*conp = negate_expr (*conp);
if (neg_var_p)
var = negate_expr (var);
}
else if (TREE_CONSTANT (in))
*conp = in;
@ -952,9 +959,12 @@ split_tree (in, code, conp, litp, negate_p)
if (negate_p)
{
var = negate_expr (var);
if (*litp)
*minus_litp = *litp, *litp = 0;
else if (*minus_litp)
*litp = *minus_litp, *minus_litp = 0;
*conp = negate_expr (*conp);
*litp = negate_expr (*litp);
var = negate_expr (var);
}
return var;
@ -962,9 +972,7 @@ split_tree (in, code, conp, litp, negate_p)
/* Re-associate trees split by the above function. T1 and T2 are either
expressions to associate or null. Return the new expression, if any. If
we build an operation, do it in TYPE and with CODE, except if CODE is a
MINUS_EXPR, in which case we use PLUS_EXPR since split_tree will already
have taken care of the negations. */
we build an operation, do it in TYPE and with CODE. */
static tree
associate_trees (t1, t2, code, type)
@ -977,9 +985,6 @@ associate_trees (t1, t2, code, type)
else if (t2 == 0)
return t1;
if (code == MINUS_EXPR)
code = PLUS_EXPR;
/* If either input is CODE, a PLUS_EXPR, or a MINUS_EXPR, don't
try to fold this since we will have infinite recursion. But do
deal with any NEGATE_EXPRs. */
@ -3805,8 +3810,8 @@ optimize_minmax_comparison (t)
other operations already in T. WIDE_TYPE, if non-null, is a type that
should be used for the computation if wider than our type.
For example, if we are dividing (X * 8) + (Y + 16) by 4, we can return
(X * 2) + (Y + 4). We must, however, be assured that either the original
For example, if we are dividing (X * 8) + (Y * 16) by 4, we can return
(X * 2) + (Y * 4). We must, however, be assured that either the original
expression would not overflow or that overflow is undefined for the type
in the language in question.
@ -5078,24 +5083,68 @@ fold (expr)
&& (! FLOAT_TYPE_P (type)
|| (flag_unsafe_math_optimizations && code == MULT_EXPR)))
{
tree var0, con0, lit0, var1, con1, lit1;
tree var0, con0, lit0, minus_lit0;
tree var1, con1, lit1, minus_lit1;
/* Split both trees into variables, constants, and literals. Then
associate each group together, the constants with literals,
then the result with variables. This increases the chances of
literals being recombined later and of generating relocatable
expressions for the sum of a constant and literal. */
var0 = split_tree (arg0, code, &con0, &lit0, 0);
var1 = split_tree (arg1, code, &con1, &lit1, code == MINUS_EXPR);
var0 = split_tree (arg0, code, &con0, &lit0, &minus_lit0, 0);
var1 = split_tree (arg1, code, &con1, &lit1, &minus_lit1,
code == MINUS_EXPR);
/* Only do something if we found more than two objects. Otherwise,
nothing has changed and we risk infinite recursion. */
if (2 < ((var0 != 0) + (var1 != 0) + (con0 != 0) + (con1 != 0)
+ (lit0 != 0) + (lit1 != 0)))
if (2 < ((var0 != 0) + (var1 != 0)
+ (con0 != 0) + (con1 != 0)
+ (lit0 != 0) + (lit1 != 0)
+ (minus_lit0 != 0) + (minus_lit1 != 0)))
{
/* Recombine MINUS_EXPR operands by using PLUS_EXPR. */
if (code == MINUS_EXPR)
code = PLUS_EXPR;
var0 = associate_trees (var0, var1, code, type);
con0 = associate_trees (con0, con1, code, type);
lit0 = associate_trees (lit0, lit1, code, type);
minus_lit0 = associate_trees (minus_lit0, minus_lit1, code, type);
/* Preserve the MINUS_EXPR if the negative part of the literal is
greater than the positive part. Otherwise, the multiplicative
folding code (i.e extract_muldiv) may be fooled in case
unsigned constants are substracted, like in the following
example: ((X*2 + 4) - 8U)/2. */
if (minus_lit0 && lit0)
{
if (tree_int_cst_lt (lit0, minus_lit0))
{
minus_lit0 = associate_trees (minus_lit0, lit0,
MINUS_EXPR, type);
lit0 = 0;
}
else
{
lit0 = associate_trees (lit0, minus_lit0,
MINUS_EXPR, type);
minus_lit0 = 0;
}
}
if (minus_lit0)
{
if (con0 == 0)
return convert (type, associate_trees (var0, minus_lit0,
MINUS_EXPR, type));
else
{
con0 = associate_trees (con0, minus_lit0,
MINUS_EXPR, type);
return convert (type, associate_trees (var0, con0,
PLUS_EXPR, type));
}
}
con0 = associate_trees (con0, lit0, code, type);
return convert (type, associate_trees (var0, con0, code, type));
}

33
gcc/testsuite/gcc.c-torture/execute/20020423-1.c Normal file
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@ -0,0 +1,33 @@
/* PR c/5430 */
/* Verify that the multiplicative folding code is not fooled
by the mix between signed variables and unsigned constants. */
extern void abort (void);
extern void exit (int);
int main (void)
{
int my_int = 924;
unsigned int result;
result = ((my_int*2 + 4) - 8U) / 2;
if (result != 922U)
abort();
result = ((my_int*2 - 4U) + 2) / 2;
if (result != 923U)
abort();
result = (((my_int + 2) * 2) - 8U - 4) / 2;
if (result != 920U)
abort();
result = (((my_int + 2) * 2) - (8U + 4)) / 2;
if (result != 920U)
abort();
result = ((my_int*4 + 2U) - 4U) / 2;
if (result != 1847U)
abort();
exit(0);
}