On 11/28/22 08:38, Maciej W. Rozycki wrote:
On Mon, 28 Nov 2022, Jeff Law wrote:
LGTM, but with a nit, I don't get set.w but get an andi like below, so
maybe we should also scan-assembler-not andi? feel free to commit that
directly with that fix
```asm
sleu:
sgtu a0,a0,a1 # 9 [c=4 l=4] *sgtu_disi
xori a0,a0,1 # 10 [c=4 l=4] *xorsi3_internal/1
andi a0,a0,1 # 16 [c=4 l=4] anddi3/1
ret # 25 [c=0 l=4] simple_return
```
Interesting. I can do that, but can you please share the compilation
options, given or defaulted (from `--with...' configuration options), this
happens with?
I have noticed it went nowhere. Can you please check what compilation
options lead to this discrepancy so that we can have the fix included in
GCC 13? I'd like to understand what's going on here.
FWIW, I don't see the redundant sign extension with this testcase at -O2 on
the trunk. Is it possible the patch has been made redundant over the last few
months?
Maybe at -O2, but the test cases continue to fail in my configuration for
other optimisation levels:
FAIL: gcc.target/riscv/sge.c -O1 scan-assembler-not sext\\.w
FAIL: gcc.target/riscv/sge.c -Og -g scan-assembler-not sext\\.w
FAIL: gcc.target/riscv/sgeu.c -O1 scan-assembler-not sext\\.w
FAIL: gcc.target/riscv/sgeu.c -Og -g scan-assembler-not sext\\.w
FAIL: gcc.target/riscv/sle.c -O1 scan-assembler-not sext\\.w
FAIL: gcc.target/riscv/sle.c -Og -g scan-assembler-not sext\\.w
FAIL: gcc.target/riscv/sleu.c -O1 scan-assembler-not sext\\.w
FAIL: gcc.target/riscv/sleu.c -Og -g scan-assembler-not sext\\.w
I may have been running an rv32 toolchain... So I'll start over and
ensure that I'm running rv64 :-)
With the trunk, I get code like Kito (AND with 0x1 mask)
The key difference is Roger's patch:
commit c23a9c87cc62bd177fd0d4db6ad34b34e1b9a31f
Author: Roger Sayle <ro...@nextmovesoftware.com>
Date: Wed Aug 3 08:55:35 2022 +0100
Some additional zero-extension related optimizations in simplify-rtx.
This patch implements some additional zero-extension and sign-extension
related optimizations in simplify-rtx.cc. The original motivation
comes
from PR rtl-optimization/71775, where in comment #2 Andrew Pinksi sees:
Failed to match this instruction:
(set (reg:DI 88 [ _1 ])
(sign_extend:DI (subreg:SI (ctz:DI (reg/v:DI 86 [ x ])) 0)))
[ ... ]
With that patch the sign extension is removed and instead we generate
the AND with 0x1.
Old, from combine dump:
Successfully matched this instruction:
(set (reg/i:DI 10 a0)
! (sign_extend:DI (reg:SI 78)))
New, from combine dump:
(set (reg/i:DI 10 a0)
! (and:DI (subreg:DI (reg:SI 78) 0)
! (const_int 1 [0x1])))
Note the date on Roger's patch, roughly the same time as yours. I
suspect Kito had tested the truck with Roger's patch.
Your patch is probably still useful. I think Kito's only concern was to
make sure we don't have the ANDI instruction in addition to not having
the SEXT instruction. So still approved for trunk, just update the
testcases to make sure we don't have the ANDI too.
jeff
