https://gcc.gnu.org/g:800b3977031dd4f14d09ced975276e09457dfff7
commit r16-25-g800b3977031dd4f14d09ced975276e09457dfff7
Author: Andrew Pinski <quic_apin...@quicinc.com>
Date: Mon Apr 7 17:06:17 2025 -0700
DSE: Support triming of some more memset [PR87901]
DSE has support for trimming memset (and memset like) statements.
In this case we have `MEM <unsigned char[17]> [(char * {ref-all})&z] = {};`
in
the IR and when we go to trim it, we call build_fold_addr_expr which leaves
around
a cast from one pointer type to another. This is due to build_fold_addr_expr
being generic but in gimple you don't need these casts.
PR tree-optimization/87901
gcc/ChangeLog:
* tree-ssa-dse.cc (maybe_trim_constructor_store): Strip over
useless type
conversions after taking the address of the MEM_REF.
gcc/testsuite/ChangeLog:
* gcc.dg/tree-ssa/ssa-dse-52.c: New test.
Signed-off-by: Andrew Pinski <quic_apin...@quicinc.com>
Diff:
---
gcc/testsuite/gcc.dg/tree-ssa/ssa-dse-52.c | 30 ++++++++++++++++++++++++++++++
gcc/tree-ssa-dse.cc | 2 ++
2 files changed, 32 insertions(+)
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/ssa-dse-52.c
b/gcc/testsuite/gcc.dg/tree-ssa/ssa-dse-52.c
new file mode 100644
index 000000000000..9e605ac8b1f5
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/ssa-dse-52.c
@@ -0,0 +1,30 @@
+/* { dg-options "-O2 -fdump-tree-dse-details -fno-tree-fre
-fdump-tree-optimized" } */
+
+/* PR tree-optimization/87901 */
+
+char z[32];
+void foo1(void)
+{
+ char z1[17];
+ char z2[24];
+ __builtin_memset (z1, 0, 17);
+ __builtin_memcpy (z, z1, 17);
+ __builtin_memset (z2, 0, 24);
+ __builtin_memcpy (z+8, z2, 24);
+}
+
+/* we should get:
+ MEM <unsigned char[8]> [(char * {ref-all})&z] = {};
+ MEM <unsigned char[24]> [(char * {ref-all})&z + 8B] = {};
+ after DSE; trimming the first memset to z (which was memcpy) to 8 bytes
+ from the original 17.
+ and not have a [17] in the IR after DSE.
+ The two memset to z1/z2 will also be removed.
+ */
+/* { dg-final { scan-tree-dump-not "\\\[17\\\]" "optimized" } } */
+/* { dg-final { scan-tree-dump "\\\[8\\\]" "dse1" } } */
+
+/* { dg-final { scan-tree-dump-times "Trimming statement " 1 "dse1" } } */
+/* { dg-final { scan-tree-dump-times "Deleted dead call:" 2 "dse1" } } */
+
+
diff --git a/gcc/tree-ssa-dse.cc b/gcc/tree-ssa-dse.cc
index bc632e384841..82ebc99686c4 100644
--- a/gcc/tree-ssa-dse.cc
+++ b/gcc/tree-ssa-dse.cc
@@ -588,6 +588,8 @@ maybe_trim_constructor_store (ao_ref *ref, sbitmap live,
gimple *stmt)
/* We want &lhs for the MEM_REF expression. */
tree lhs_addr = build_fold_addr_expr (gimple_assign_lhs (stmt));
+ STRIP_USELESS_TYPE_CONVERSION (lhs_addr);
+
if (! is_gimple_min_invariant (lhs_addr))
return;
