https://llvm.org/bugs/show_bug.cgi?id=25509
Bug ID: 25509
Summary: [LIR] Misses simple memset case
Product: libraries
Version: trunk
Hardware: PC
OS: Windows NT
Status: NEW
Severity: normal
Priority: P
Component: Loop Optimizer
Assignee: unassignedb...@nondot.org
Reporter: mcros...@codeaurora.org
CC: llvm-bugs@lists.llvm.org
Classification: Unclassified
LLVM is unable to generate a memset from the below test:
void test(int *arr) {
for (int i = 0; i < 1024; ++i) {
arr[i] = 0;
arr[i+1024] = 0;
}
}
As of r252817 clang produces:
test: // @test
// BB#0: // %entry
mov x8, xzr
movi v0.2d, #0000000000000000
.LBB0_1: // %vector.body
// =>This Inner Loop Header: Depth=1
add x9, x0, x8
add x8, x8, #16 // =16
str q0, [x9]
str q0, [x9, #4096]
cmp x8, #1, lsl #12 // =4096
b.ne .LBB0_1
// BB#2: // %for.cond.cleanup
ret
GCC is able to generate 2 memsets (one per arr access). If I'm not mistaken
this can be transformed into a single memset (i.e., memset(arr, 0, 2048)).
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