ping
https://gcc.gnu.org/ml/gcc-patches/2018-08/msg00108.html
On 08/01/2018 04:07 PM, Sam Tebbs wrote:
Hi all,
This patch adds an optimisation that exploits the AArch64 BFXIL
instruction when or-ing the result of two bitwise and operations
with non-overlapping bitmasks
(e.g. (a & 0xFFFF0000) | (b & 0x0000FFFF)).
Example:
unsigned long long combine(unsigned long long a, unsigned long
long b) {
return (a & 0xffffffff00000000ll) | (b & 0x00000000ffffffffll);
}
void read(unsigned long long a, unsigned long long b, unsigned
long long *c) {
*c = combine(a, b);
}
When compiled with -O2, read would result in:
read:
and x5, x1, #0xffffffff
and x4, x0, #0xffffffff00000000
orr x4, x4, x5
str x4, [x2]
ret
But with this patch results in:
read:
mov x4, x0
bfxil x4, x1, 0, 32
str x4, [x2]
ret
Bootstrapped and regtested on aarch64-none-linux-gnu and
aarch64-none-elf with no regressions.
gcc/
2018-08-01 Sam Tebbs<[email protected]>
PR target/85628
* config/aarch64/aarch64.md (*aarch64_bfxil):
Define.
* config/aarch64/constraints.md (Ulc): Define
* config/aarch64/aarch64-protos.h
(aarch64_is_left_consecutive): Define.
* config/aarch64/aarch64.c (aarch64_is_left_consecutive):
New function.
gcc/testsuite
2018-08-01 Sam Tebbs<[email protected]>
PR target/85628
* gcc.target/aarch64/combine_bfxil.c: New file.
* gcc.target/aarch64/combine_bfxil_2.c: New file.
