https://gcc.gnu.org/g:e7d5b9aa021f6fc32810670b18ffabe543262775
commit r15-3548-ge7d5b9aa021f6fc32810670b18ffabe543262775
Author: Richard Biener <rguent...@suse.de>
Date: Wed Aug 28 14:06:48 2024 +0200
tree-optimization/116514 - handle pointer difference in bit-CCP
When evaluating the difference of two aligned pointers in CCP we
fail to handle the EXACT_DIV_EXPR by the element size that occurs.
The testcase then also exercises modulo to test alignment but
modulo by a power-of-two isn't handled either.
PR tree-optimization/116514
* tree-ssa-ccp.cc (bit_value_binop): Handle EXACT_DIV_EXPR
like TRUNC_DIV_EXPR. Handle exact division of a signed value
by a power-of-two like a shift. Handle unsigned division by
a power-of-two like a shift.
Handle unsigned TRUNC_MOD_EXPR by power-of-two, handle signed
TRUNC_MOD_EXPR by power-of-two if the result is zero.
* gcc.dg/tree-ssa/ssa-ccp-44.c: New testcase.
Diff:
---
gcc/testsuite/gcc.dg/tree-ssa/ssa-ccp-44.c | 13 +++++++++++++
gcc/tree-ssa-ccp.cc | 27 ++++++++++++++++++++++++++-
2 files changed, 39 insertions(+), 1 deletion(-)
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/ssa-ccp-44.c
b/gcc/testsuite/gcc.dg/tree-ssa/ssa-ccp-44.c
new file mode 100644
index 000000000000..f1f09bfb1170
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/ssa-ccp-44.c
@@ -0,0 +1,13 @@
+/* { dg-do compile } */
+/* { dg-options "-O -fdump-tree-ccp1" } */
+
+int
+test(int* a, int* b)
+{
+ __INTPTR_TYPE__ delta = (int*)__builtin_assume_aligned(b, 32)
+ - (int*)__builtin_assume_aligned(a, 32);
+ __INTPTR_TYPE__ x = delta % 8;
+ return (x == 0);
+}
+
+/* { dg-final { scan-tree-dump "return 1;" "ccp1" } } */
diff --git a/gcc/tree-ssa-ccp.cc b/gcc/tree-ssa-ccp.cc
index 47b2ce9441e5..a5f6ef5f5ddd 100644
--- a/gcc/tree-ssa-ccp.cc
+++ b/gcc/tree-ssa-ccp.cc
@@ -1921,6 +1921,27 @@ bit_value_binop (enum tree_code code, signop sgn, int
width,
{
widest_int r1max = r1val | r1mask;
widest_int r2max = r2val | r2mask;
+ if (r2mask == 0)
+ {
+ widest_int shift = wi::exact_log2 (r2val);
+ if (shift != -1)
+ {
+ // Handle modulo by a power of 2 as a bitwise and.
+ widest_int tem_val, tem_mask;
+ bit_value_binop (BIT_AND_EXPR, sgn, width, &tem_val, &tem_mask,
+ r1type_sgn, r1type_precision, r1val, r1mask,
+ r2type_sgn, r2type_precision,
+ r2val - 1, r2mask);
+ if (sgn == UNSIGNED
+ || !wi::neg_p (r1max)
+ || (tem_mask == 0 && tem_val == 0))
+ {
+ *val = tem_val;
+ *mask = tem_mask;
+ return;
+ }
+ }
+ }
if (sgn == UNSIGNED
|| (!wi::neg_p (r1max) && !wi::neg_p (r2max)))
{
@@ -1949,11 +1970,15 @@ bit_value_binop (enum tree_code code, signop sgn, int
width,
}
break;
+ case EXACT_DIV_EXPR:
case TRUNC_DIV_EXPR:
{
widest_int r1max = r1val | r1mask;
widest_int r2max = r2val | r2mask;
- if (r2mask == 0 && !wi::neg_p (r1max))
+ if (r2mask == 0
+ && (code == EXACT_DIV_EXPR
+ || sgn == UNSIGNED
+ || !wi::neg_p (r1max)))
{
widest_int shift = wi::exact_log2 (r2val);
if (shift != -1)
