https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63175
--- Comment #16 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to Richard Biener from comment #15)
> Btw, first of all unaligned stores are not supported according to the targets
> vectorization hook, thus you'd need to peel the loop to make the store
> aligned
> which for some reason doesn't happen.
Quite obvious - the loop iterates 8 times but the vectorization factor is 8
as well, so if we peel off a iteration to align the destination the vectorized
loop will never enter.
Why is the loop bound to i != 16 / sizeof *s?
> But when peeled you certainly will see
> byte/short/word stores at least.
Like when I increase the iteration count I get for copy_short_0_1:
.L.copy_Type_0_1:
addis 6,2,.LANCHOR0@toc@ha
addis 7,2,.LANCHOR1@toc@ha
addi 6,6,.LANCHOR0@toc@l
addi 7,7,.LANCHOR1@toc@l
li 8,7
addi 9,6,2
mr 10,7
mtctr 8
.p2align 4,,15
.L2:
addi 10,10,2
lhz 8,-2(10)
addi 9,9,2
sth 8,-2(9)
bdnz .L2
addi 8,7,14
addi 7,7,29
neg 5,8
lvx 1,0,8
lvx 0,0,7
li 7,16
lvsr 13,0,5
addi 8,10,14
addi 9,9,14
addi 10,10,16
vperm 0,1,0,13
stvx 0,6,7
.p2align 4,,15
.L3:
lhzu 7,2(8)
cmpld 7,10,8
sthu 7,2(9)
bne+ 7,.L3
blr
the cost model should probably reject this, but it does not:
t.c:36:1: note: Cost model analysis:
Vector inside of loop cost: 3
Vector prologue cost: 17
Vector epilogue cost: 2
Scalar iteration cost: 2
Scalar outside cost: 0
Vector outside cost: 19
prologue iterations: 7
epilogue iterations: 1
Calculated minimum iters for profitability: 10
