When recording store for RTL dead store elimination, check if the source
register is set only once to a constant. If yes, record the constant
as the store source. It eliminates unrolled zero stores after memset 0
in a loop where a vector register is used as the zero store source.
gcc/
PR rtl-optimization/105638
* dse.cc (record_store): Use the constant source if the source
register is set only once.
gcc/testsuite/
PR rtl-optimization/105638
* g++.target/i386/pr105638.C: New test.
---
gcc/dse.cc | 19 ++++++++++
gcc/testsuite/g++.target/i386/pr105638.C | 44 ++++++++++++++++++++++++
2 files changed, 63 insertions(+)
create mode 100644 gcc/testsuite/g++.target/i386/pr105638.C
diff --git a/gcc/dse.cc b/gcc/dse.cc
index 30c11cee034..0433dd3d846 100644
--- a/gcc/dse.cc
+++ b/gcc/dse.cc
@@ -1508,6 +1508,25 @@ record_store (rtx body, bb_info_t bb_info)
if (tem && CONSTANT_P (tem))
const_rhs = tem;
+ else
+ {
+ /* If RHS is set only once to a constant, set CONST_RHS
+ to the constant. */
+ df_ref def = DF_REG_DEF_CHAIN (REGNO (rhs));
+ if (def != nullptr
+ && !DF_REF_IS_ARTIFICIAL (def)
+ && !DF_REF_NEXT_REG (def))
+ {
+ rtx_insn *def_insn = DF_REF_INSN (def);
+ rtx def_body = PATTERN (def_insn);
+ if (GET_CODE (def_body) == SET)
+ {
+ rtx def_src = SET_SRC (def_body);
+ if (CONSTANT_P (def_src))
+ const_rhs = def_src;
+ }
+ }
+ }
}
}
diff --git a/gcc/testsuite/g++.target/i386/pr105638.C
b/gcc/testsuite/g++.target/i386/pr105638.C
new file mode 100644
index 00000000000..ff40a459de1
--- /dev/null
+++ b/gcc/testsuite/g++.target/i386/pr105638.C
@@ -0,0 +1,44 @@
+/* { dg-do compile { target { ! ia32 } } } */
+/* { dg-options "-std=gnu++20 -O2 -march=skylake" } */
+/* { dg-final { scan-assembler-not "vpxor" } } */
+
+#include <stdint.h>
+#include <vector>
+#include <tr1/array>
+
+class FastBoard {
+public:
+ typedef std::pair<int, int> movescore_t;
+ typedef std::tr1::array<movescore_t, 24> scoredlist_t;
+
+protected:
+ std::vector<int> m_critical;
+
+ int m_boardsize;
+};
+
+class FastState {
+public:
+ FastBoard board;
+
+ int movenum;
+protected:
+ FastBoard::scoredlist_t scoredmoves;
+};
+
+class KoState : public FastState {
+private:
+ std::vector<uint64_t> ko_hash_history;
+ std::vector<uint64_t> hash_history;
+};
+
+class GameState : public KoState {
+public:
+ void foo ();
+private:
+ std::vector<KoState> game_history;
+};
+
+void GameState::foo() {
+ game_history.resize(movenum);
+}
--
2.36.1
