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re PR tree-optimization/14796 ([tree-ssa] combine two shifts into one)

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2005-06-12  James A. Morrison  <phython@gcc.gnu.org>

        PR tree-optimization/14796
        * fold-const.c (fold_binary): Transform (A >> C) << C into
        one BIT_AND_EXPR.
        <shift>: Transform (A OP c1) OP c2 into A OP (c1 + c2).

From-SVN: r100853
This commit is contained in:
James A. Morrison 2005-06-12 08:03:23 +00:00
parent 4ae234b0a1
commit e3d025cb0d
5 changed files with 101 additions and 0 deletions
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7
gcc/ChangeLog
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@ -1,3 +1,10 @@
2005-06-12 James A. Morrison <phython@gcc.gnu.org>
PR tree-optimization/14796
* fold-const.c (fold_binary): Transform (A >> C) << C into
one BIT_AND_EXPR.
<shift>: Transform (A OP c1) OP c2 into A OP (c1 + c2).
2005-06-11 Geoffrey Keating <geoffk@apple.com>
* config/rs6000/predicates.md (reg_or_arith_cint_operand): Delete.

53
gcc/fold-const.c
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@ -8742,6 +8742,59 @@ fold_binary (enum tree_code code, tree type, tree op0, tree op1)
don't try to compute it in the compiler. */
if (TREE_CODE (arg1) == INTEGER_CST && tree_int_cst_sgn (arg1) < 0)
return NULL_TREE;
/* Turn (a OP c1) OP c2 into a OP (c1+c2). */
if (TREE_CODE (arg0) == code && host_integerp (arg1, false)
&& TREE_INT_CST_LOW (arg1) < TYPE_PRECISION (type)
&& host_integerp (TREE_OPERAND (arg0, 1), false)
&& TREE_INT_CST_LOW (TREE_OPERAND (arg0, 1)) < TYPE_PRECISION (type))
{
HOST_WIDE_INT low = (TREE_INT_CST_LOW (TREE_OPERAND (arg0, 1))
+ TREE_INT_CST_LOW (arg1));
/* Deal with a OP (c1 + c2) being undefined but (a OP c1) OP c2
being well defined. */
if (low >= TYPE_PRECISION (type))
{
if (code == LROTATE_EXPR || code == RROTATE_EXPR)
low = low % TYPE_PRECISION (type);
else if (TYPE_UNSIGNED (type) || code == LSHIFT_EXPR)
return build_int_cst (type, 0);
else
low = TYPE_PRECISION (type) - 1;
}
return fold_build2 (code, type, TREE_OPERAND (arg0, 0),
build_int_cst (type, low));
}
/* Transform (x >> c) << c into x & (-1<<c) */
if (code == LSHIFT_EXPR && TREE_CODE (arg0) == RSHIFT_EXPR
&& host_integerp (arg1, false)
&& TREE_INT_CST_LOW (arg1) < TYPE_PRECISION (type)
&& host_integerp (TREE_OPERAND (arg0, 1), false)
&& TREE_INT_CST_LOW (TREE_OPERAND (arg0, 1)) < TYPE_PRECISION (type))
{
HOST_WIDE_INT low0 = TREE_INT_CST_LOW (TREE_OPERAND (arg0, 1));
HOST_WIDE_INT low1 = TREE_INT_CST_LOW (arg1);
unsigned HOST_WIDE_INT low;
HOST_WIDE_INT high;
tree lshift;
tree arg00;
if (low0 == low1)
{
arg00 = fold_convert (type, TREE_OPERAND (arg0, 0));
lshift_double (-1, -1, low0 < low1 ? low0 : low1,
TYPE_PRECISION (type), &low, &high, 1);
lshift = build_int_cst_wide (type, low, high);
return fold_build2 (BIT_AND_EXPR, type, arg00, lshift);
}
}
/* Rewrite an LROTATE_EXPR by a constant into an
RROTATE_EXPR by a new constant. */
if (code == LROTATE_EXPR && TREE_CODE (arg1) == INTEGER_CST)

5
gcc/testsuite/ChangeLog
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@ -1,3 +1,8 @@
2005-06-12 James A. Morrison <phython@gcc.gnu.org>
* gcc.dg/pr14796-1.c: New.
* gcc.dg/pr14796-2.c: New.
2005-06-11 Steven G. Kargl <kargls@comcast.net>
PR fortran/17792

14
gcc/testsuite/gcc.dg/pr14796-1.c Normal file
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@ -0,0 +1,14 @@
/* { dg-do compile } */
/* { dg-options "-fdump-tree-gimple" } */
int f (int a) {
return (a << 3) << 6;
}
int g (int b) {
return (b >> 5) << 5;
}
/* { dg-final { scan-tree-dump "a << 9" "gimple" } } */
/* { dg-final { scan-tree-dump "b & -32" "gimple" } } */
/* { dg-final { cleanup-tree-dump "gimple" } } */

22
gcc/testsuite/gcc.dg/pr14796-2.c Normal file
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@ -0,0 +1,22 @@
/* { dg-do compile } */
/* { dg-options "-fdump-tree-gimple" } */
int f (int a) {
return (a << 31) << 6;
}
unsigned int g (unsigned int a) {
return (a >> 7) >> 25;
}
int h (int b) {
return (b >> 30) >> 30;
}
long long j (long long c) {
return (c >> 35) << 35;
}
/* { dg-final { scan-tree-dump-times "= 0" 2 "gimple" } } */
/* { dg-final { scan-tree-dump "b >> 31" "gimple" } } */
/* { dg-final { scan-tree-dump "c & -34359738368" "gimple" } } */
/* { dg-final { cleanup-tree-dump "gimple" } } */