https://bugs.llvm.org/show_bug.cgi?id=45863
Bug ID: 45863
Summary: __restrict on struct member has no effect
Product: clang
Version: trunk
Hardware: PC
OS: All
Status: NEW
Severity: enhancement
Priority: P
Component: C++
Assignee: unassignedclangb...@nondot.org
Reporter: dshar...@google.com
CC: blitzrak...@gmail.com, dgre...@apple.com,
erik.pilking...@gmail.com, llvm-bugs@lists.llvm.org,
richard-l...@metafoo.co.uk
The following code demonstrates the issue:
const int N = 8;
void add1(const float* __restrict a, const float* __restrict b, float*
__restrict c) {
for (int i = 0; i < N; i++) {
c[i] = a[i] + b[i];
}
}
struct A {
float * __restrict x;
};
void add2(const A& a, const A& b, A& c) {
for (int i = 0; i < N; i++) {
c.x[i] = a.x[i] + b.x[i];
}
}
When compiling this with clang -S -O2 -march=native, I see a vectorized loop
for add1, but not for add2. When I look at the generated LLVM assembly, there's
no indication that the noalias attribute was applied to any of the pointers.
Adding __restrict to the function argument references does not help either (but
I wouldn't expect it to).
As far as I can tell, this is supposed to work to indicate that none of the x
pointers in add2 alias, at least in C.
I just tried this on a recently updated trunk Clang+LLVM and see the same
behavior (commit 57fb56b30e8).
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