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* [gcc r14-2731] RISC-V: optim const DF +0.0 store to mem [PR/110748]
@ 2023-07-22 21:45 Vineet Gupta
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From: Vineet Gupta @ 2023-07-22 21:45 UTC (permalink / raw)
To: gcc-cvs
https://gcc.gnu.org/g:ecfa870ff29d979bd2c3d411643b551f2b6915b0
commit r14-2731-gecfa870ff29d979bd2c3d411643b551f2b6915b0
Author: Vineet Gupta <vineetg@rivosinc.com>
Date: Thu Jul 20 11:15:37 2023 -0700
RISC-V: optim const DF +0.0 store to mem [PR/110748]
Fixes: ef85d150b5963 ("RISC-V: Enable TARGET_SUPPORTS_WIDE_INT")
DF +0.0 is bitwise all zeros so int x0 store to mem can be used to optimize it.
void zd(double *) { *d = 0.0; }
currently:
| fmv.d.x fa5,zero
| fsd fa5,0(a0)
| ret
With patch
| sd zero,0(a0)
| ret
The fix updates predicate const_0_operand() so reg_or_0_operand () now
includes const_double, enabling movdf expander -> riscv_legitimize_move ()
to generate below vs. an intermediate set (reg:DF) const_double:DF
| (insn 6 3 0 2 (set (mem:DF (reg/v/f:DI 134 [ d ])
| (const_double:DF 0.0 [0x0.0p+0]))
This change also enables such insns to be recog() by later passes.
The md pattern "*movdf_hardfloat_rv64" despite already supporting the
needed constraints {"m","G"} mem/const 0.0 was failing to match because
the additional condition check reg_or_0_operand() was failing due to
missing const_double.
This failure to recog() was triggering an ICE when testing the in-flight
f-m-o patches and is how all of this started, but then was deemed to be
an independent optimization of it's own [1].
[1] https://gcc.gnu.org/pipermail/gcc-patches/2023-July/624857.html
Its worthwhile to note all the set peices were already there and working
up until my own commit mentioned at top regressed the whole thing.
Ran thru full multilib testsuite and no surprises. There was 1 false
failure due to random string "lw" appearing in lto build assembler output,
which is also fixed here.
gcc/ChangeLog:
PR target/110748
* config/riscv/predicates.md (const_0_operand): Add back
const_double.
gcc/testsuite/ChangeLog:
* gcc.target/riscv/pr110748-1.c: New Test.
* gcc.target/riscv/xtheadfmv-fmv.c: Add '\t' around test
patterns to avoid random string matches.
Signed-off-by: Vineet Gupta <vineetg@rivosinc.com>
Diff:
---
gcc/config/riscv/predicates.md | 2 +-
gcc/testsuite/gcc.target/riscv/pr110748-1.c | 10 ++++++++++
gcc/testsuite/gcc.target/riscv/xtheadfmv-fmv.c | 8 ++++----
3 files changed, 15 insertions(+), 5 deletions(-)
diff --git a/gcc/config/riscv/predicates.md b/gcc/config/riscv/predicates.md
index 5a22c77f0cd..9db28c2def7 100644
--- a/gcc/config/riscv/predicates.md
+++ b/gcc/config/riscv/predicates.md
@@ -58,7 +58,7 @@
(match_test "INTVAL (op) + 1 != 0")))
(define_predicate "const_0_operand"
- (and (match_code "const_int,const_wide_int,const_vector")
+ (and (match_code "const_int,const_wide_int,const_double,const_vector")
(match_test "op == CONST0_RTX (GET_MODE (op))")))
(define_predicate "const_1_operand"
diff --git a/gcc/testsuite/gcc.target/riscv/pr110748-1.c b/gcc/testsuite/gcc.target/riscv/pr110748-1.c
new file mode 100644
index 00000000000..2f5bc08aae7
--- /dev/null
+++ b/gcc/testsuite/gcc.target/riscv/pr110748-1.c
@@ -0,0 +1,10 @@
+/* { dg-do compile } */
+/* { dg-require-effective-target hard_float } */
+/* { dg-options "-march=rv64g -mabi=lp64d -O2" } */
+
+
+void zd(double *d) { *d = 0.0; }
+void zf(float *f) { *f = 0.0; }
+
+/* { dg-final { scan-assembler-not "\tfmv\\.d\\.x\t" } } */
+/* { dg-final { scan-assembler-not "\tfmv\\.s\\.x\t" } } */
diff --git a/gcc/testsuite/gcc.target/riscv/xtheadfmv-fmv.c b/gcc/testsuite/gcc.target/riscv/xtheadfmv-fmv.c
index 1036044291e..89eb48bed1b 100644
--- a/gcc/testsuite/gcc.target/riscv/xtheadfmv-fmv.c
+++ b/gcc/testsuite/gcc.target/riscv/xtheadfmv-fmv.c
@@ -18,7 +18,7 @@ d2ll (double d)
/* { dg-final { scan-assembler "th.fmv.hw.x" } } */
/* { dg-final { scan-assembler "fmv.x.w" } } */
/* { dg-final { scan-assembler "th.fmv.x.hw" } } */
-/* { dg-final { scan-assembler-not "sw" } } */
-/* { dg-final { scan-assembler-not "fld" } } */
-/* { dg-final { scan-assembler-not "fsd" } } */
-/* { dg-final { scan-assembler-not "lw" } } */
+/* { dg-final { scan-assembler-not "\tsw\t" } } */
+/* { dg-final { scan-assembler-not "\tfld\t" } } */
+/* { dg-final { scan-assembler-not "\tfsd\t" } } */
+/* { dg-final { scan-assembler-not "\tlw\t" } } */
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