[gcc r12-7050] Adjust LSHIFT_EXPR handling of multiple_of_p
Richard Biener
rguenth@gcc.gnu.org
Fri Feb 4 11:54:52 GMT 2022
https://gcc.gnu.org/g:24c72fb0eedfe7c67f9b15aa31b474a999cc4723
commit r12-7050-g24c72fb0eedfe7c67f9b15aa31b474a999cc4723
Author: Richard Biener <rguenther@suse.de>
Date: Mon Jan 24 15:26:46 2022 +0100
Adjust LSHIFT_EXPR handling of multiple_of_p
This removes the odd check of size_type_node when handling left-shifts
as multiplications of 1 << N and instead uses the type as specified.
It also moves left-shift handling next to multiplications where it
semantically belongs.
2022-01-24 Richard Biener <rguenther@suse.de>
* fold-const.cc (multiple_of_p): Re-write and move LSHIFT_EXPR
handling.
Diff:
---
gcc/fold-const.cc | 33 ++++++++++++++++-----------------
1 file changed, 16 insertions(+), 17 deletions(-)
diff --git a/gcc/fold-const.cc b/gcc/fold-const.cc
index 8fc01cdfb77..12732d39c79 100644
--- a/gcc/fold-const.cc
+++ b/gcc/fold-const.cc
@@ -14079,7 +14079,7 @@ int
multiple_of_p (tree type, const_tree top, const_tree bottom)
{
gimple *stmt;
- tree t1, op1, op2;
+ tree op1, op2;
if (operand_equal_p (top, bottom, 0))
return 1;
@@ -14125,6 +14125,21 @@ multiple_of_p (tree type, const_tree top, const_tree bottom)
return (multiple_of_p (type, TREE_OPERAND (top, 1), bottom)
|| multiple_of_p (type, TREE_OPERAND (top, 0), bottom));
+ case LSHIFT_EXPR:
+ /* Handle X << CST as X * (1 << CST) and only process the constant. */
+ if (TREE_CODE (TREE_OPERAND (top, 1)) == INTEGER_CST)
+ {
+ op1 = TREE_OPERAND (top, 1);
+ if (wi::to_widest (op1) < TYPE_PRECISION (type))
+ {
+ wide_int mul_op
+ = wi::one (TYPE_PRECISION (type)) << wi::to_wide (op1);
+ return multiple_of_p (type,
+ wide_int_to_tree (type, mul_op), bottom);
+ }
+ }
+ return 0;
+
case MINUS_EXPR:
/* It is impossible to prove if op0 - op1 is multiple of bottom
precisely, so be conservative here checking if both op0 and op1
@@ -14144,22 +14159,6 @@ multiple_of_p (tree type, const_tree top, const_tree bottom)
return (multiple_of_p (type, op1, bottom)
&& multiple_of_p (type, TREE_OPERAND (top, 0), bottom));
- case LSHIFT_EXPR:
- if (TREE_CODE (TREE_OPERAND (top, 1)) == INTEGER_CST)
- {
- op1 = TREE_OPERAND (top, 1);
- /* const_binop may not detect overflow correctly,
- so check for it explicitly here. */
- if (wi::gtu_p (TYPE_PRECISION (TREE_TYPE (size_one_node)),
- wi::to_wide (op1))
- && (t1 = fold_convert (type,
- const_binop (LSHIFT_EXPR, size_one_node,
- op1))) != 0
- && !TREE_OVERFLOW (t1))
- return multiple_of_p (type, t1, bottom);
- }
- return 0;
-
CASE_CONVERT:
/* Can't handle conversions from non-integral or wider integral type. */
if ((TREE_CODE (TREE_TYPE (TREE_OPERAND (top, 0))) != INTEGER_TYPE)
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