https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63503
--- Comment #10 from Wilco <wdijkstr at arm dot com> ---
The loops shown are not the correct inner loops for those options - with
-ffast-math they are vectorized. LLVM unrolls 2x but GCC doesn't. So the
question is why GCC doesn't unroll vectorized loops like LLVM?
GCC:
.L24:
ldr q3, [x13, x5]
add x6, x6, 1
ldr q2, [x16, x5]
cmp x6, x12
add x5, x5, 16
fmla v1.2d, v3.2d, v2.2d
bcc .L24
LLVM:
.LBB2_12:
ldur q2, [x8, #-16]
ldr q3, [x8], #32
ldur q4, [x21, #-16]
ldr q5, [x21], #32
fmla v1.2d, v2.2d, v4.2d
fmla v0.2d, v3.2d, v5.2d
sub x30, x30, #4 // =4
cbnz x30, .LBB2_12
