https://gcc.gnu.org/g:8be088a0f395047189e139d4c791cfc2275898b9
commit 8be088a0f395047189e139d4c791cfc2275898b9
Author: Jeff Law <j...@ventanamicro.com>
Date: Mon May 13 07:14:08 2024 -0600
[to-be-committed,RISC-V] Improve single inverted bit extraction - v3
So this patch fixes a minor code generation inefficiency that (IIRC) the
RAU team discovered a while ago in spec.
If we want the inverted value of a single bit we can use bext to extract
the bit, then seq to invert the value (if viewed as a 0/1 truth value).
The RTL is fairly convoluted, but it's basically a right shift to get
the bit into position, bitwise-not then masking off all but the low bit.
So it's a 3->2 combine, hidden by the fact that and-not is a
define_insn_and_split, so it actually looks like a 2->2 combine.
We've run this through Ventana's internal CI (which includes
zba_zbb_zbs) and I've run it in my own tester (rv64gc, rv32gcv). I'll
wait for the upstream CI to finish with positive results before pushing.
gcc/
* config/riscv/bitmanip.md (bextseqzdisi): New patterns.
gcc/testsuite/
* gcc.target/riscv/zbs-bext-2.c: New test.
* gcc.target/riscv/zbs-bext.c: Fix one of the possible expectes
sequences.
(cherry picked from commit 0c585c8d0dd85601a8d116ada99126a48c8ce9fd)
Diff:
---
gcc/config/riscv/.riscv.cc.swo | Bin 0 -> 417792 bytes
gcc/config/riscv/bitmanip.md | 43 ++++++++++++++++++++++++++++
gcc/config/riscv/j | 0
gcc/testsuite/gcc.target/riscv/zbs-bext-2.c | 19 ++++++++++++
gcc/testsuite/gcc.target/riscv/zbs-bext.c | 2 +-
5 files changed, 63 insertions(+), 1 deletion(-)
diff --git a/gcc/config/riscv/.riscv.cc.swo b/gcc/config/riscv/.riscv.cc.swo
new file mode 100644
index 000000000000..77ed37353bee
Binary files /dev/null and b/gcc/config/riscv/.riscv.cc.swo differ
diff --git a/gcc/config/riscv/bitmanip.md b/gcc/config/riscv/bitmanip.md
index d76a72d30e02..724511b6df3b 100644
--- a/gcc/config/riscv/bitmanip.md
+++ b/gcc/config/riscv/bitmanip.md
@@ -711,6 +711,49 @@
"bext\t%0,%1,%2"
[(set_attr "type" "bitmanip")])
+;; This is a bext followed by a seqz. Normally this would be a 3->2 split
+;; But the and-not pattern with a constant operand is a define_insn_and_split,
+;; so this looks like a 2->2 split, which combine rejects. So implement it
+;; as a define_insn_and_split as well.
+(define_insn_and_split "*bextseqzdisi"
+ [(set (match_operand:DI 0 "register_operand" "=r")
+ (and:DI
+ (not:DI
+ (subreg:DI
+ (lshiftrt:SI
+ (match_operand:SI 1 "register_operand" "r")
+ (match_operand:QI 2 "register_operand" "r")) 0))
+ (const_int 1)))]
+ "TARGET_64BIT && TARGET_ZBS"
+ "#"
+ "&& 1"
+ [(set (match_dup 0)
+ (zero_extract:DI (match_dup 1)
+ (const_int 1)
+ (zero_extend:DI (match_dup 2))))
+ (set (match_dup 0) (eq:DI (match_dup 0) (const_int 0)))]
+ "operands[1] = gen_lowpart (word_mode, operands[1]);"
+ [(set_attr "type" "bitmanip")])
+
+(define_insn_and_split "*bextseqzdisi"
+ [(set (match_operand:X 0 "register_operand" "=r")
+ (and:X
+ (not:X
+ (lshiftrt:X
+ (match_operand:X 1 "register_operand" "r")
+ (match_operand:QI 2 "register_operand" "r")))
+ (const_int 1)))]
+ "TARGET_ZBS"
+ "#"
+ "&& 1"
+ [(set (match_dup 0)
+ (zero_extract:X (match_dup 1)
+ (const_int 1)
+ (zero_extend:X (match_dup 2))))
+ (set (match_dup 0) (eq:X (match_dup 0) (const_int 0)))]
+ "operands[1] = gen_lowpart (word_mode, operands[1]);"
+ [(set_attr "type" "bitmanip")])
+
;; When performing `(a & (1UL << bitno)) ? 0 : -1` the combiner
;; usually has the `bitno` typed as X-mode (i.e. no further
;; zero-extension is performed around the bitno).
diff --git a/gcc/config/riscv/j b/gcc/config/riscv/j
new file mode 100644
index 000000000000..e69de29bb2d1
diff --git a/gcc/testsuite/gcc.target/riscv/zbs-bext-2.c
b/gcc/testsuite/gcc.target/riscv/zbs-bext-2.c
new file mode 100644
index 000000000000..79f120b22863
--- /dev/null
+++ b/gcc/testsuite/gcc.target/riscv/zbs-bext-2.c
@@ -0,0 +1,19 @@
+/* { dg-do compile } */
+/* { dg-options "-march=rv64gc_zbs -mabi=lp64" } */
+/* { dg-skip-if "" { *-*-* } { "-O0" "-Og" } } */
+
+
+_Bool match(const int ch, int fMap) {
+ return ((fMap & (1<<(ch))) == 0);
+}
+
+_Bool match2(const int ch, int fMap) {
+ return ((fMap & (1UL<<(ch))) == 0);
+}
+
+
+/* { dg-final { scan-assembler-times "bext\t" 2 } } */
+/* { dg-final { scan-assembler-times "seqz\t|xori\t" 2 } } */
+/* { dg-final { scan-assembler-not "sraw\t" } } */
+/* { dg-final { scan-assembler-not "not\t" } } */
+/* { dg-final { scan-assembler-not "andi\t" } } */
diff --git a/gcc/testsuite/gcc.target/riscv/zbs-bext.c
b/gcc/testsuite/gcc.target/riscv/zbs-bext.c
index ff75dad65285..0db97f5ab596 100644
--- a/gcc/testsuite/gcc.target/riscv/zbs-bext.c
+++ b/gcc/testsuite/gcc.target/riscv/zbs-bext.c
@@ -38,7 +38,7 @@ long bext64_4(long a, char bitno)
/* { dg-final { scan-assembler-times "bexti\t" 1 } } */
/* { dg-final { scan-assembler-times "bext\t" 5 } } */
-/* { dg-final { scan-assembler-times "xori\t|snez\t" 1 } } */
+/* { dg-final { scan-assembler-times "xori\t|seqz\t" 1 } } */
/* { dg-final { scan-assembler-times "addi\t" 1 } } */
/* { dg-final { scan-assembler-times "neg\t" 1 } } */
/* { dg-final { scan-assembler-not {\mandi} } } */
