https://llvm.org/bugs/show_bug.cgi?id=26167
Bug ID: 26167
Summary: Loop vectorizer fails to maximize the use of
__builtin_assume()
Product: tools
Version: 3.7
Hardware: All
OS: All
Status: NEW
Severity: normal
Priority: P
Component: opt
Assignee: unassignedb...@nondot.org
Reporter: mar...@synopsys.com
CC: llvm-bugs@lists.llvm.org
Classification: Unclassified
I've been able to get the loop vectorizer to understand that the number of
iterations is positive, but I can't get it to understand it's both positive and
will iterate an even number of times. A scalar loop is produced for each of the
following test cases.
void vcpy1(short* restrict d, const char* restrict l, const char* restrict r,
int N) {
__builtin_assume( (N > 1) && (N%2 == 0) );
#pragma clang loop vectorize(enable) vectorize_width(2)
for (int j=0;j<N;j++)
d[j] = l[j] + r[j];
}
void vcpy2(short* restrict d, const char* restrict l, const char* restrict r,
int N) {
__builtin_assume( (N > 1) && ((N&1) == 0) );
#pragma clang loop vectorize(enable) vectorize_width(2)
for (int j=0;j<N;j++)
d[j] = l[j] + r[j];
}
void vcpy3(short* restrict d, const char* restrict l, const char* restrict r,
int N) {
__builtin_assume(N > 1);
__builtin_assume(N%2 == 0);
#pragma clang loop vectorize(enable) vectorize_width(2)
for (int j=0;j<N;j++)
d[j] = l[j] + r[j];
}
void vcpy4(short* restrict d, const char* restrict l, const char* restrict r,
int N) {
__builtin_assume(N > 1);
__builtin_assume((N&1) == 0);
#pragma clang loop vectorize(enable) vectorize_width(2)
for (int j=0;j<N;j++)
d[j] = l[j] + r[j];
}
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