https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91198
Bug ID: 91198
Summary: GCC not generating AVX-512 compress/expand
instructions
Product: gcc
Version: 10.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: moritz.kreutzer at siemens dot com
Target Milestone: ---
We have a simple loop to select values based on a condition from one array and
store the selected values contiguously in a second array:
https://godbolt.org/z/T7UXXD
================================
float const threshold = 0.5;
int o = 0;
for (int i = 0; i < size; ++i) {
if (input[i] < threshold) {
output[o] = input[i];
o++;
}
}
================================
It seems like GCC is not able to generate AVX-512 assembly using vcompressps
instructions for this code. The same holds true for the orthogonal pattern
(expansion using vexpandps). Is this a missed optimization in GCC or is there
another issue in the example code which prevents vectorization?
