在 2026/5/2 下午10:49, Xi Ruoyao 写道:
Copy the a ^ b ^ (a | c) => (a &~ c) ^ b optimization from RISC-V zbb
(r17-241) as we have the andn instruction in LA64 and LA32S.
I have a doubt—is this derivation formula written incorrectly?
if a = 0, b = 0, c = 1
a ^ b ^ (a | c) = 0 ^ 0 ^ (0 | 1) = 1
(a & ~c) ^ b = (0 & ~1 ) & 0 = 0
PR rtl-optimization/96692
gcc/
* config/loongarch/loongarch.md (define_split): New splitters
turning a ^ b ^ (a | c) => (a &~ c) ^ b.
gcc/testsuite/
* gcc.target/loongarch/pr96692.c: New test.
---
Bootstrapped and regtested on loongarch64-linux-gnu. Ok for trunk?
gcc/config/loongarch/loongarch.md | 23 ++++++++++++++++++++
gcc/testsuite/gcc.target/loongarch/pr96692.c | 11 ++++++++++
2 files changed, 34 insertions(+)
create mode 100644 gcc/testsuite/gcc.target/loongarch/pr96692.c
diff --git a/gcc/config/loongarch/loongarch.md
b/gcc/config/loongarch/loongarch.md
index 1fea712f668..f3c08b521dd 100644
--- a/gcc/config/loongarch/loongarch.md
+++ b/gcc/config/loongarch/loongarch.md
@@ -1829,6 +1829,29 @@ (define_insn "*<optab>nsi_internal"
"<insn>n\t%0,%2,%1"
[(set_attr "type" "logical")
(set_attr "mode" "SI")])
+
+(define_split
+ [(set (match_operand:X 0 "register_operand")
+ (xor:X (xor:X (ior:X (match_operand:X 1 "register_operand")
+ (match_operand:X 2 "register_operand"))
+ (match_dup 1))
+ (match_operand:X 3 "register_operand")))
+ (clobber (match_operand:X 4 "register_operand"))]
+ "TARGET_64BIT || TARGET_32BIT_S"
+ [(set (match_dup 4) (and:X (not:X (match_dup 1)) (match_dup 2)))
+ (set (match_dup 0) (xor:X (match_dup 4) (match_dup 3)))])
+
+(define_split
+ [(set (match_operand:X 0 "register_operand")
+ (xor:X (xor:X (ior:X (match_operand:X 1 "register_operand")
+ (match_operand:X 2 "register_operand"))
+ (match_dup 2))
+ (match_operand:X 3 "register_operand")))
+ (clobber (match_operand:X 4 "register_operand"))]
+ "TARGET_64BIT || TARGET_32BIT_S"
+ [(set (match_dup 4) (and:X (not:X (match_dup 2)) (match_dup 1)))
+ (set (match_dup 0) (xor:X (match_dup 4) (match_dup 3)))])
+
;;
;; ....................
diff --git a/gcc/testsuite/gcc.target/loongarch/pr96692.c
b/gcc/testsuite/gcc.target/loongarch/pr96692.c
new file mode 100644
index 00000000000..1c2011af264
--- /dev/null
+++ b/gcc/testsuite/gcc.target/loongarch/pr96692.c
@@ -0,0 +1,11 @@
+/* { dg-do compile } */
+/* { dg-options "-march=loongarch64 -O" { target lp64 } } */
+/* { dg-options "-march=la32v1.0 -O" { target ilp32 } } */
+
+int f(int a, int b, int c)
+{
+ return (a ^ b) ^ (a | c);
+}
+
+/* { dg-final { scan-assembler-times "xor\t" 1 } } */
+/* { dg-final { scan-assembler-times "andn\t" 1 } } */
