[Bug target/88013] can't vectorize rgb to grayscale conversion code
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88013 Andrew Pinski changed: What|Removed |Added Severity|normal |enhancement
[Bug target/88013] can't vectorize rgb to grayscale conversion code
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88013 --- Comment #9 from krux --- (In reply to ktkachov from comment #7) > I tried current trunk (future GCC 9) > GCC 9 learned to avoid excessive widening during vectorisation, which is > what accounts for the large number of instructions you see. Confirmed, the loop is now as described in comment #5 with trunk gcc. Still with vshr+vmovn as mentioned by Ramana. But by the way, the tail is completely unrolled, 15x the following, seems quite excessive to me: ldrbip, [r1, #1]@ zero_extendqisi2 movsr6, #151 ldrblr, [r1]@ zero_extendqisi2 movsr5, #77 ldrbr7, [r1, #2]@ zero_extendqisi2 movsr4, #28 smulbb ip, ip, r6 smlabb lr, r5, lr, ip add ip, r3, #1 smlabb r7, r4, r7, lr cmp ip, r2 asr r7, r7, #8 strbr7, [r0] bge .L1 assert(n >= 16) helps a bit, but n % 16 == 0 doesn't.
[Bug target/88013] can't vectorize rgb to grayscale conversion code
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88013 Ramana Radhakrishnan changed: What|Removed |Added Status|UNCONFIRMED |NEW Last reconfirmed||2018-12-14 CC||ramana at gcc dot gnu.org Ever confirmed|0 |1 --- Comment #8 from Ramana Radhakrishnan --- > vshr.u16q9, q9, #8 > vshr.u16q8, q8, #8 > vmovn.i16 d20, q9 > vmovn.i16 d21, q8 Isn't that "just" a missing combine pattern to get us vshrn in both backends ? Ramana
[Bug target/88013] can't vectorize rgb to grayscale conversion code
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88013 --- Comment #7 from ktkachov at gcc dot gnu.org --- I tried current trunk (future GCC 9) GCC 9 learned to avoid excessive widening during vectorisation, which is what accounts for the large number of instructions you see.
[Bug target/88013] can't vectorize rgb to grayscale conversion code
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88013
--- Comment #6 from krux ---
-mfloat-abi=hard was missing indeed. It's a pity there's no warning like when
trying to use the intrinsics.
Still I see a lot more instructions, maybe that got fixed after v7.2?
https://godbolt.org/z/OWzgXi
vld3.8 {d16, d18, d20}, [r3]
add ip, r3, #24
add lr, lr, #1
add r3, r3, #48
cmp lr, r5
vld3.8 {d17, d19, d21}, [ip]
vmovl.u8 q5, d16
vmovl.u8 q15, d18
vmovl.u8 q11, d17
vmovl.u8 q4, d19
vmovl.u8 q0, d20
vmovl.u8 q1, d21
vmull.s16 q6, d10, d28
vmull.s16 q3, d22, d28
vmull.s16 q2, d30, d26
vmull.s16 q11, d23, d29
vmull.s16 q15, d31, d27
vmull.s16 q5, d11, d29
vmull.s16 q9, d8, d26
vmull.s16 q8, d9, d27
vadd.i32 q2, q6, q2
vadd.i32 q10, q5, q15
vadd.i32 q9, q3, q9
vmull.s16 q15, d0, d24
vadd.i32 q8, q11, q8
vmull.s16 q3, d2, d24
vmull.s16 q0, d1, d25
vmull.s16 q1, d3, d25
vadd.i32 q11, q2, q15
vadd.i32 q9, q9, q3
vadd.i32 q10, q10, q0
vadd.i32 q8, q8, q1
vshr.s32 q11, q11, #8
vshr.s32 q9, q9, #8
vshr.s32 q10, q10, #8
vshr.s32 q8, q8, #8
vmovn.i32 d30, q11
vmovn.i32 d31, q10
vmovn.i32 d20, q9
vmovn.i32 d21, q8
vmovn.i16 d16, q15
vmovn.i16 d17, q10
vst1.8 {q8}, [r4]
[Bug target/88013] can't vectorize rgb to grayscale conversion code
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88013
ktkachov at gcc dot gnu.org changed:
What|Removed |Added
CC||ktkachov at gcc dot gnu.org
--- Comment #5 from ktkachov at gcc dot gnu.org ---
I see vectorisation for arm (and aarch64 FWIW):
-O3 -march=armv8-a -mfpu=neon-fp-armv8 -mfloat-abi=hard
gives the loop:
.L4:
mov r3, lr
add lr, lr, #48
vld3.8 {d16, d18, d20}, [r3]!
vld3.8 {d17, d19, d21}, [r3]
vmull.u8 q12, d16, d30
vmull.u8 q1, d18, d28
vmull.u8 q2, d19, d29
vmull.u8 q11, d17, d31
vmull.u8 q3, d20, d26
vadd.i16q12, q12, q1
vmull.u8 q10, d21, d27
vadd.i16q8, q11, q2
vadd.i16q9, q12, q3
vadd.i16q8, q8, q10
vshr.u16q9, q9, #8
vshr.u16q8, q8, #8
vmovn.i16 d20, q9
vmovn.i16 d21, q8
vst1.8 {q10}, [ip]!
cmp ip, r4
bne .L4
Though of course it's not as tight as the assembly given in the link
[Bug target/88013] can't vectorize rgb to grayscale conversion code
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88013 --- Comment #4 from krux --- On x64 indeed both compilers generate a huge amount of code. https://godbolt.org/z/TH7mqn
[Bug target/88013] can't vectorize rgb to grayscale conversion code
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88013 --- Comment #3 from krux --- A few NEON instructions are sufficient: https://web.archive.org/web/20170227190422/http://hilbert-space.de/?p=22 clang seems to generate similar code, see the godbolt links.
[Bug target/88013] can't vectorize rgb to grayscale conversion code
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88013 Richard Biener changed: What|Removed |Added Keywords||missed-optimization Target||arm Blocks||53947 --- Comment #2 from Richard Biener --- On x86_64 we manage to vectorize this with quite absymal code (for core-avx2) with a vectorization factor of 32: .L4: vmovdqu (%rax), %ymm1 vmovdqu 64(%rax), %ymm4 addq$32, %rcx addq$96, %rax vmovdqu -64(%rax), %ymm5 vpshufb %ymm14, %ymm1, %ymm0 vpermq $78, %ymm0, %ymm2 vpshufb %ymm13, %ymm1, %ymm0 vpshufb %ymm12, %ymm5, %ymm3 vpor%ymm2, %ymm0, %ymm0 vpshufb %ymm11, %ymm4, %ymm2 vpor%ymm3, %ymm0, %ymm0 vpermq $78, %ymm2, %ymm3 vpshufb .LC5(%rip), %ymm4, %ymm2 vpshufb .LC4(%rip), %ymm0, %ymm0 vpor%ymm3, %ymm2, %ymm2 vpshufb .LC6(%rip), %ymm1, %ymm3 vpermq $78, %ymm3, %ymm15 vpor%ymm2, %ymm0, %ymm0 vpshufb .LC7(%rip), %ymm1, %ymm3 vpshufb .LC8(%rip), %ymm5, %ymm2 vpor%ymm15, %ymm3, %ymm3 vpshufb .LC11(%rip), %ymm4, %ymm15 vpshufb .LC14(%rip), %ymm5, %ymm5 vpor%ymm2, %ymm3, %ymm3 vpshufb .LC9(%rip), %ymm4, %ymm2 vpermq $78, %ymm2, %ymm2 vpshufb %ymm10, %ymm3, %ymm3 vpor%ymm2, %ymm15, %ymm2 vpor%ymm2, %ymm3, %ymm3 vpshufb .LC12(%rip), %ymm1, %ymm2 vpshufb .LC13(%rip), %ymm1, %ymm1 vpermq $78, %ymm2, %ymm2 vpor%ymm2, %ymm1, %ymm2 vpshufb .LC15(%rip), %ymm4, %ymm1 vpshufb .LC16(%rip), %ymm4, %ymm4 vpermq $78, %ymm1, %ymm1 vpor%ymm5, %ymm2, %ymm2 vpor%ymm1, %ymm4, %ymm4 vpshufb %ymm10, %ymm2, %ymm2 vpmovzxbw %xmm0, %ymm1 vpor%ymm4, %ymm2, %ymm2 vpmovzxbw %xmm3, %ymm4 vextracti128$0x1, %ymm0, %xmm0 vpmullw %ymm7, %ymm4, %ymm4 vpmullw %ymm8, %ymm1, %ymm1 vextracti128$0x1, %ymm3, %xmm3 vpmovzxbw %xmm0, %ymm0 vpmovzxbw %xmm3, %ymm3 vpmullw %ymm8, %ymm0, %ymm0 vpmullw %ymm7, %ymm3, %ymm3 vpaddw %ymm4, %ymm1, %ymm1 vpmovzxbw %xmm2, %ymm4 vextracti128$0x1, %ymm2, %xmm2 vpmovzxbw %xmm2, %ymm2 vpmullw %ymm6, %ymm4, %ymm4 vpmullw %ymm6, %ymm2, %ymm2 vpaddw %ymm3, %ymm0, %ymm0 vpaddw %ymm4, %ymm1, %ymm1 vpaddw %ymm2, %ymm0, %ymm0 vpsrlw $8, %ymm1, %ymm1 vpsrlw $8, %ymm0, %ymm0 vpand %ymm1, %ymm9, %ymm1 vpand %ymm0, %ymm9, %ymm0 vpackuswb %ymm0, %ymm1, %ymm0 vpermq $216, %ymm0, %ymm0 vmovdqu %ymm0, -32(%rcx) cmpq%r8, %rcx jne .L4 Maybe you can post what you think arm can do better here? Referenced Bugs: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53947 [Bug 53947] [meta-bug] vectorizer missed-optimizations
[Bug target/88013] can't vectorize rgb to grayscale conversion code
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88013 --- Comment #1 from krux --- Something like -march=armv8-a -mfpu=neon-fp-armv8 does not work either. https://godbolt.org/z/MpBQ0I
