https://gcc.gnu.org/g:3c0f3b74bf6011b12fe12821ba6e1079309d9445
commit r16-1290-g3c0f3b74bf6011b12fe12821ba6e1079309d9445
Author: Vineet Gupta <vine...@rivosinc.com>
Date: Sun Jun 8 14:55:01 2025 -0700
RISC-V: frm/mode-switch: Reduce FRM restores on DYN transition [PR119164]
FRM mode switching state machine has DYN as default state which it also
fallsback to after transitioning to other states such as DYN_CALL.
Currently TARGET_MODE_EMIT generates a FRM restore on any transition to
DYN leading to spurious/extraneous FRM restores.
Only do this if an interim static Rounding Mode was observed in the state
machine.
Fixes the extraneous FRM read/write in PR119164 (and also PR119832 w/o need
for TARGET_MODE_CONFLUENCE). Also reduces the number of FRM writes in
SPEC2017 -Ofast -mrv64gcv build significantly.
Before After
------------- -------------
frrm fsrmi fsrm frrm fsrmi frrm
perlbench_r 42 0 4 17 0 1
cpugcc_r 167 0 17 11 0 0
bwaves_r 16 0 1 16 0 1
mcf_r 11 0 0 11 0 0
cactusBSSN_r 76 0 27 19 0 1
namd_r 119 0 63 14 0 1
parest_r 168 0 114 24 0 1
povray_r 123 1 17 26 1 6
lbm_r 6 0 0 6 0 0
omnetpp_r 17 0 1 17 0 1
wrf_r 2287 13 1956 1268 13 1603
cpuxalan_r 17 0 1 17 0 1
ldecod_r 11 0 0 11 0 0
x264_r 14 0 1 11 0 0
blender_r 724 12 182 61 12 42
cam4_r 324 13 169 45 13 20
deepsjeng_r 11 0 0 11 0 0
imagick_r 265 16 34 132 16 25
leela_r 12 0 0 12 0 0
nab_r 13 0 1 13 0 1
exchange2_r 16 0 1 16 0 1
fotonik3d_r 20 0 11 19 0 1
roms_r 33 0 23 21 0 1
xz_r 6 0 0 6 0 0
--------------- --------------
4498 55 2623 1804 55 1707
--------------- --------------
7176 3566
--------------- --------------
PR target/119164
gcc/ChangeLog:
* config/riscv/riscv.cc (riscv_emit_frm_mode_set): check
STATIC_FRM_P for transition to DYN.
gcc/testsuite/ChangeLog:
* gcc.target/riscv/rvv/base/pr119164.c: New test.
Signed-off-by: Vineet Gupta <vine...@rivosinc.com>
Diff:
---
gcc/config/riscv/riscv.cc | 2 +-
gcc/testsuite/gcc.target/riscv/rvv/base/pr119164.c | 22 ++++++++++++++++++++++
2 files changed, 23 insertions(+), 1 deletion(-)
diff --git a/gcc/config/riscv/riscv.cc b/gcc/config/riscv/riscv.cc
index a1bb51af2be4..1e56ee5dcb63 100644
--- a/gcc/config/riscv/riscv.cc
+++ b/gcc/config/riscv/riscv.cc
@@ -12277,7 +12277,7 @@ riscv_emit_frm_mode_set (int mode, int prev_mode)
&& prev_mode != riscv_vector::FRM_DYN
&& prev_mode != riscv_vector::FRM_DYN_CALL)
/* Restore frm value when switch to DYN mode. */
- || (mode == riscv_vector::FRM_DYN
+ || (STATIC_FRM_P (cfun) && mode == riscv_vector::FRM_DYN
&& prev_mode != riscv_vector::FRM_DYN_CALL);
if (restore_p)
diff --git a/gcc/testsuite/gcc.target/riscv/rvv/base/pr119164.c
b/gcc/testsuite/gcc.target/riscv/rvv/base/pr119164.c
new file mode 100644
index 000000000000..a39a7f177f05
--- /dev/null
+++ b/gcc/testsuite/gcc.target/riscv/rvv/base/pr119164.c
@@ -0,0 +1,22 @@
+/* Reduced from SPEC2017 blender: node_texture_util.c.
+ The conditional function call was tripping mode switching state machine */
+
+/* { dg-do compile } */
+/* { dg-options " -Ofast -march=rv64gcv_zvl256b -ftree-vectorize
-mrvv-vector-bits=zvl" } */
+
+void *a;
+float *b;
+short c;
+void d();
+void e() {
+ if (a)
+ d();
+ if (c) {
+ b[0] = b[0] * 0.5f + 0.5f;
+ b[1] = b[1] * 0.5f + 0.5f;
+ }
+}
+
+/* { dg-final { scan-assembler-not {frrm\s+[axs][0-9]+} } } */
+/* { dg-final { scan-assembler-not {fsrmi\s+[01234]} } } */
+/* { dg-final { scan-assembler-not {fsrm\s+[axs][0-9]+} } } */
