Use Zbs when generating a sequence for
"if ((a & twobits) == singlebit) ..."
that can be expressed as
bexti + bexti + andn.
gcc/ChangeLog:
* config/riscv/bitmanip.md
(*branch<X:mode>_mask_twobits_equals_singlebit):
Handle "if ((a & T) == C)" using Zbs, when T has 2 bits set and C
has one of these tow bits set.
* config/riscv/predicates.md (const_twobits_not_arith_operand):
New predicate.
gcc/testsuite/ChangeLog:
* gcc.target/riscv/zbs-if_then_else-01.c: New test.
Signed-off-by: Philipp Tomsich <philipp.toms...@vrull.eu>
---
Changes in v2:
- Convert the FAIL into a gcc_assert.
- Merge the !SMALL_OPERAND check into a new predicate.
- Some of the predicates moved into the other patch of the series due to
the order the reviews were processed.
gcc/config/riscv/bitmanip.md | 42 +++++++++++++++++++
gcc/config/riscv/predicates.md | 5 +++
.../gcc.target/riscv/zbs-if_then_else-01.c | 20 +++++++++
3 files changed, 67 insertions(+)
create mode 100644 gcc/testsuite/gcc.target/riscv/zbs-if_then_else-01.c
diff --git a/gcc/config/riscv/bitmanip.md b/gcc/config/riscv/bitmanip.md
index d7c64270c00..be53aecbb13 100644
--- a/gcc/config/riscv/bitmanip.md
+++ b/gcc/config/riscv/bitmanip.md
@@ -517,3 +517,45 @@ (define_insn_and_split "*andi<mode>_extrabit"
operands[3] = GEN_INT (bits | topbit);
operands[4] = GEN_INT (~topbit);
})
+
+;; IF_THEN_ELSE: test for 2 bits of opposite polarity
+(define_insn_and_split "*branch<X:mode>_mask_twobits_equals_singlebit"
+ [(set (pc)
+ (if_then_else
+ (match_operator 1 "equality_operator"
+ [(and:X (match_operand:X 2 "register_operand" "r")
+ (match_operand:X 3 "const_twobits_not_arith_operand" "i"))
+ (match_operand:X 4 "single_bit_mask_operand" "i")])
+ (label_ref (match_operand 0 "" ""))
+ (pc)))
+ (clobber (match_scratch:X 5 "=&r"))
+ (clobber (match_scratch:X 6 "=&r"))]
+ "TARGET_ZBS && TARGET_ZBB"
+ "#"
+ "&& reload_completed"
+ [(set (match_dup 5) (zero_extract:X (match_dup 2)
+ (const_int 1)
+ (match_dup 8)))
+ (set (match_dup 6) (zero_extract:X (match_dup 2)
+ (const_int 1)
+ (match_dup 9)))
+ (set (match_dup 6) (and:X (not:X (match_dup 6)) (match_dup 5)))
+ (set (pc) (if_then_else (match_op_dup 1 [(match_dup 6) (const_int 0)])
+ (label_ref (match_dup 0))
+ (pc)))]
+{
+ unsigned HOST_WIDE_INT twobits_mask = UINTVAL (operands[3]);
+ unsigned HOST_WIDE_INT singlebit_mask = UINTVAL (operands[4]);
+
+ /* We should never see an unsatisfiable condition. */
+ gcc_assert (twobits_mask & singlebit_mask);
+
+ int setbit = ctz_hwi (singlebit_mask);
+ int clearbit = ctz_hwi (twobits_mask & ~singlebit_mask);
+
+ operands[1] = gen_rtx_fmt_ee (GET_CODE (operands[1]) == NE ? EQ : NE,
+ <X:MODE>mode, operands[6], GEN_INT(0));
+
+ operands[8] = GEN_INT (setbit);
+ operands[9] = GEN_INT (clearbit);
+})
diff --git a/gcc/config/riscv/predicates.md b/gcc/config/riscv/predicates.md
index 3300c0e36eb..9e2f7c9b6b3 100644
--- a/gcc/config/riscv/predicates.md
+++ b/gcc/config/riscv/predicates.md
@@ -296,6 +296,11 @@ (define_predicate "const_twobits_operand"
(and (match_code "const_int")
(match_test "popcount_hwi (UINTVAL (op)) == 2")))
+(define_predicate "const_twobits_not_arith_operand"
+ (and (match_code "const_int")
+ (and (not (match_operand 0 "arith_operand"))
+ (match_operand 0 "const_twobits_operand"))))
+
;; A CONST_INT operand that fits into the unsigned half of a
;; signed-immediate after the top bit has been cleared
(define_predicate "uimm_extra_bit_operand"
diff --git a/gcc/testsuite/gcc.target/riscv/zbs-if_then_else-01.c
b/gcc/testsuite/gcc.target/riscv/zbs-if_then_else-01.c
new file mode 100644
index 00000000000..d249a841ff9
--- /dev/null
+++ b/gcc/testsuite/gcc.target/riscv/zbs-if_then_else-01.c
@@ -0,0 +1,20 @@
+/* { dg-do compile } */
+/* { dg-options "-march=rv64gc_zbb_zbs -mabi=lp64" } */
+/* { dg-skip-if "" { *-*-* } { "-O0" "-Og" "-O1" } } */
+
+void g();
+
+void f1 (long a)
+{
+ if ((a & ((1ul << 33) | (1 << 4))) == (1ul << 33))
+ g();
+}
+
+void f2 (long a)
+{
+ if ((a & 0x12) == 0x10)
+ g();
+}
+
+/* { dg-final { scan-assembler-times "bexti\t" 2 } } */
+/* { dg-final { scan-assembler-times "andn\t" 1 } } */
--
2.34.1
