https://gcc.gnu.org/g:10d76b7f1e5b63ad6d2b92940c39007913ced037
commit r15-5185-g10d76b7f1e5b63ad6d2b92940c39007913ced037
Author: Jeff Law <j...@ventanamicro.com>
Date: Tue Nov 12 17:12:49 2024 -0700
Reapply "[PATCH v2] RISC-V: zero_extend(not) -> xor optimization [PR112398]"
This reverts commit de3b277247ce98d189f121155b75f490725a42f6.
Diff:
---
gcc/simplify-rtx.cc | 22 ++++++++++++++++++++++
gcc/testsuite/gcc.target/riscv/pr112398.c | 14 ++++++++++++++
2 files changed, 36 insertions(+)
diff --git a/gcc/simplify-rtx.cc b/gcc/simplify-rtx.cc
index 893c5f6e1ae0..d05efac20dc8 100644
--- a/gcc/simplify-rtx.cc
+++ b/gcc/simplify-rtx.cc
@@ -1842,6 +1842,28 @@ simplify_context::simplify_unary_operation_1 (rtx_code
code, machine_mode mode,
& ~GET_MODE_MASK (op_mode)) == 0)
return SUBREG_REG (op);
+ /* Trying to optimize:
+ (zero_extend:M (subreg:N (not:M (X:M)))) ->
+ (xor:M (zero_extend:M (subreg:N (X:M)), mask))
+ where the mask is GET_MODE_MASK (N).
+ For the cases when X:M doesn't have any non-zero bits
+ outside of mode N, (zero_extend:M (subreg:N (X:M))
+ will be simplified to just (X:M)
+ and whole optimization will be -> (xor:M (X:M, mask)). */
+ if (SUBREG_P (op)
+ && GET_CODE (XEXP (op, 0)) == NOT
+ && GET_MODE (XEXP (op, 0)) == mode
+ && subreg_lowpart_p (op)
+ && GET_MODE_SIZE (GET_MODE (op)).is_constant ()
+ && (nonzero_bits (XEXP (XEXP (op, 0), 0), mode)
+ & ~GET_MODE_MASK (mode)) == 0)
+ {
+ const uint64_t mask = GET_MODE_MASK (GET_MODE (op));
+ return simplify_gen_binary (XOR, mode,
+ XEXP (XEXP (op, 0), 0),
+ gen_int_mode (mask, mode));
+ }
+
#if defined(POINTERS_EXTEND_UNSIGNED)
/* As we do not know which address space the pointer is referring to,
we can do this only if the target does not support different pointer
diff --git a/gcc/testsuite/gcc.target/riscv/pr112398.c
b/gcc/testsuite/gcc.target/riscv/pr112398.c
new file mode 100644
index 000000000000..624a665b76c9
--- /dev/null
+++ b/gcc/testsuite/gcc.target/riscv/pr112398.c
@@ -0,0 +1,14 @@
+/* { dg-do compile } */
+/* { dg-options "-march=rv64gc -mabi=lp64d" } */
+/* { dg-skip-if "" { *-*-* } { "-O0" "-Og" } } */
+
+#include <stdint.h>
+
+uint8_t neg_u8 (const uint8_t src)
+{
+ return ~src;
+}
+
+/* { dg-final { scan-assembler-times "xori\t" 1 } } */
+/* { dg-final { scan-assembler-not "not\t" } } */
+/* { dg-final { scan-assembler-not "andi\t" } } */
