On 6/15/2026 7:35 AM, Milan Tripkovic wrote:
This patch implement new pattern for match.pd that recognize the
sign-extension idiom (x & low_bits) - (x & sign_bit) and tests that covers it.
Pattern is based on conversation from bug report.
TRUNK riscv output:
sext8_hd:
andi a5,a0,127
andi a0,a0,128
sub a0,a5,a0
ret
sext16_hd:
slli a5,a0,49
li a4,32768
srli a5,a5,49
and a0,a0,a4
sub a0,a5,a0
ret
NEW riscv output:
sext8_hd:
slliw a0,a0,24
sraiw a0,a0,24
ret
sext16_hd:
slliw a0,a0,16
sraiw a0,a0,16
ret
And if the "B" extension is available those will collapse even further.
PR target/125405
gcc/ChangeLog:
* match.pd: New pattern added
gcc/testsuite/ChangeLog:
* gcc.dg/pr125405-bitint.c: New test.
* gcc.dg/tree-ssa/pr125405.c: New test.
* gcc.target/riscv/pr125405.c: New test.
I've pushed this to the trunk. FTR this bootstrapped and regression
tested on x86_64, riscv, aarch64 and probably a couple other targets in
my tester.
Jeff
