https://bugs.llvm.org/show_bug.cgi?id=42411
Bug ID: 42411
Summary: Suboptimal code after vectorization of not unrolled
loop with 8 iterations
Product: libraries
Version: trunk
Hardware: PC
OS: Linux
Status: NEW
Severity: enhancement
Priority: P
Component: Loop Optimizer
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected]
Found in PR42410.
void foo (int *__restrict arr1, int *__restrict arr2)
{
for (int i = 0; i < 8; i++)
arr1[i] += arr2[i];
}
Clang -O3 -march=skylake -fno-unroll-loops
foo(int*, int*): # @foo(int*, int*)
xor eax, eax
.LBB0_1: # =>This Inner Loop Header: Depth=1
vmovdqu ymm0, ymmword ptr [rdi + 4*rax]
vpaddd ymm0, ymm0, ymmword ptr [rsi + 4*rax]
vmovdqu ymmword ptr [rdi + 4*rax], ymm0
add rax, 8
cmp rax, 8
jne .LBB0_1
vzeroupper
ret
GCC / ICC produces with same flags:
foo(int*, int*):
vmovdqu ymm0, YMMWORD PTR [rdi] #6.5
vpaddd ymm1, ymm0, YMMWORD PTR [rsi] #6.5
vmovdqu YMMWORD PTR [rdi], ymm1 #6.5
vzeroupper #7.1
ret
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