https://gcc.gnu.org/g:7102620067eebfbfb895dccd5ddd26870178c83f
commit r15-6872-g7102620067eebfbfb895dccd5ddd26870178c83f
Author: Vineet Gupta <vine...@rivosinc.com>
Date: Sat Jan 11 11:13:19 2025 -0800
RISC-V: fix thinko in riscv_register_move_cost ()
This seeming benign mistake caused a massive SPEC2017 Cactu regression
(2.1 trillion insn to 2.5 trillion) wiping out all the gains from my
recent sched1 improvement. Thankfully the issue was trivial to fix even
if hard to isolate.
On BPI3:
Before bug
----------
| Performance counter stats for './cactusBSSN_r_base-1':
|
| 4,557,471.02 msec task-clock:u # 1.000 CPUs
utilized
| 1,245 context-switches:u # 0.273 /sec
| 1 cpu-migrations:u # 0.000 /sec
| 205,376 page-faults:u # 45.064 /sec
| 7,291,944,801,307 cycles:u # 1.600 GHz
| 2,134,835,735,951 instructions:u # 0.29 insn
per cycle
| 10,799,296,738 branches:u # 2.370 M/sec
| 15,308,966 branch-misses:u # 0.14% of
all branches
|
| 4557.710508078 seconds time elapsed
Bug
---
| Performance counter stats for './cactusBSSN_r_base-2':
|
| 4,801,813.79 msec task-clock:u # 1.000 CPUs
utilized
| 8,066 context-switches:u # 1.680 /sec
| 1 cpu-migrations:u # 0.000 /sec
| 203,836 page-faults:u # 42.450 /sec
| 7,682,826,638,790 cycles:u # 1.600 GHz
| 2,503,133,291,344 instructions:u # 0.33 insn
per cycle
^^^^^^^^^^^^^^^^^
| 10,799,287,796 branches:u # 2.249 M/sec
| 16,641,200 branch-misses:u # 0.15% of
all branches
|
| 4802.616638386 seconds time elapsed
|
Fix
---
| Performance counter stats for './cactusBSSN_r_base-3':
|
| 4,556,170.75 msec task-clock:u # 1.000 CPUs
utilized
| 1,739 context-switches:u # 0.382 /sec
| 0 cpu-migrations:u # 0.000 /sec
| 203,458 page-faults:u # 44.655 /sec
| 7,289,854,613,923 cycles:u # 1.600 GHz
| 2,134,854,070,916 instructions:u # 0.29 insn
per cycle
| 10,799,296,807 branches:u # 2.370 M/sec
| 15,403,357 branch-misses:u # 0.14% of
all branches
|
| 4556.445490123 seconds time elapsed
Fixes: 46888571d242 ("RISC-V: Add cr and cf constraint")
Signed-off-by: Vineet Gupta <vine...@rivosinc.com>
gcc/ChangeLog:
* config/riscv/riscv.cc (riscv_register_move_cost): Remove buggy
check.
Diff:
---
gcc/config/riscv/riscv.cc | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/gcc/config/riscv/riscv.cc b/gcc/config/riscv/riscv.cc
index 3b5712429e46..a03b35bb9cfd 100644
--- a/gcc/config/riscv/riscv.cc
+++ b/gcc/config/riscv/riscv.cc
@@ -9591,8 +9591,7 @@ riscv_register_move_cost (machine_mode mode,
bool from_is_gpr = from == GR_REGS || from == RVC_GR_REGS;
bool to_is_fpr = to == FP_REGS || to == RVC_FP_REGS;
bool to_is_gpr = to == GR_REGS || to == RVC_GR_REGS;
- if ((from_is_fpr && to == to_is_gpr) ||
- (from_is_gpr && to_is_fpr))
+ if ((from_is_fpr && to_is_gpr) || (from_is_gpr && to_is_fpr))
return tune_param->fmv_cost;
if (from == V_REGS)
