The patch optimizes code generation for comparisons of the form
X & C1 == C2 by converting them to (X | ~C1) == (C2 | ~C1).
C1 is a constant that requires li and addi to be loaded,
while ~C1 requires a single lui instruction.
As the values of C1 and C2 are not visible within
the equality expression, a plus pattern is matched instead.
2024-12-16 Oliver Kozul <[email protected]>
PR target/114087
gcc/ChangeLog:
* config/riscv/riscv.md (*lui_constraint<ANYI:mode>_and_to_or): New
pattern
gcc/testsuite/ChangeLog:
* gcc.target/riscv/pr114087-1.c: New test.
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---
gcc/config/riscv/riscv.md | 28 +++++++++++++++++++++
gcc/testsuite/gcc.target/riscv/pr114087-1.c | 16 ++++++++++++
2 files changed, 44 insertions(+)
create mode 100644 gcc/testsuite/gcc.target/riscv/pr114087-1.c
diff --git a/gcc/config/riscv/riscv.md b/gcc/config/riscv/riscv.md
index 3a4cd1d93a0..75b0947e597 100644
--- a/gcc/config/riscv/riscv.md
+++ b/gcc/config/riscv/riscv.md
@@ -858,6 +858,34 @@
[(set_attr "type" "arith")
(set_attr "mode" "SI")])
+;; Transform (X & C1) + C2 into (X | ~C1) - (-C2 | ~C1)
+;; Where C1 is not a LUI operand, but ~C1 is a LUI operand
+
+(define_insn_and_split "*lui_constraint<ANYI:mode>_and_to_or"
+ [(set (match_operand:ANYI 0 "register_operand" "=r")
+ (plus:ANYI (and:ANYI (match_operand:ANYI 1 "register_operand" "r")
+ (match_operand 2 "const_int_operand"))
+ (match_operand 3 "const_int_operand")))
+ (clobber (match_scratch:X 4 "=&r"))]
+ "LUI_OPERAND (~INTVAL (operands[2]))
+ && ((INTVAL (operands[2]) & (-INTVAL (operands[3])))
+ == (-INTVAL (operands[3])))
+ && riscv_const_insns (operands[3], false)
+ && (riscv_const_insns
+ (GEN_INT (~INTVAL (operands[2]) | -INTVAL (operands[3])), false)
+ <= riscv_const_insns (operands[3], false))"
+ "#"
+ "&& reload_completed"
+ [(set (match_dup 4) (match_dup 5))
+ (set (match_dup 0) (ior:X (match_dup 1) (match_dup 4)))
+ (set (match_dup 4) (match_dup 6))
+ (set (match_dup 0) (minus:X (match_dup 0) (match_dup 4)))]
+ {
+ operands[5] = GEN_INT (~INTVAL (operands[2]));
+ operands[6] = GEN_INT ((~INTVAL (operands[2])) | (-INTVAL (operands[3])));
+ }
+ [(set_attr "type" "arith")])
+
;;
;; ....................
;;
diff --git a/gcc/testsuite/gcc.target/riscv/pr114087-1.c
b/gcc/testsuite/gcc.target/riscv/pr114087-1.c
new file mode 100644
index 00000000000..9df02db6d5d
--- /dev/null
+++ b/gcc/testsuite/gcc.target/riscv/pr114087-1.c
@@ -0,0 +1,16 @@
+/* { dg-do compile } */
+/* { dg-require-effective-target rv64 } */
+/* { dg-skip-if "" { *-*-* } { "-O0" "-O1" "-Og" } } */
+/* { dg-options "-march=rv64gc -mabi=lp64d" } */
+
+#include <stdbool.h>
+#include <stdint.h>
+
+static uint32_t mask1 = 0x55555FFF;
+static uint32_t val1 = 0x14501DEF;
+
+bool pred1a(uint32_t x) {
+ return ((x & mask1) == val1);
+}
+
+/* { dg-final { scan-assembler {or\s*[a-x0-9]+,\s*[a-x0-9]+,\s*[a-x0-9]+} } }
*/
--
2.43.0
