Clang crash with -mcpu=grace -O3 -msve-vector-bits=128: error in backend: Cannot scalarize scalable vector loads

[ktkachov]

The following reduced testcase:

int a, d;
extern short b[];
long c;
void e(bool f[]) {
#pragma clang loop vectorize_predicate(enable)
  for (signed char g = 1; g < (char)d; g += 3) {
    a = f[g] ? c : 0;
    b[g] = 0;
  }
}

crashes for me with -mcpu=grace -O3 -msve-vector-bits=128:
error in backend: Cannot scalarize scalable vector loads

[fhahn]

https://clang.godbolt.org/z/cKa3v7P5K

[llvmbot]

@llvm/issue-subscribers-backend-aarch64

Author: Kyrill Tkachov (ktkachov)

The following reduced testcase: ``` int a, d; extern short b[]; long c; void e(bool f[]) { #pragma clang loop vectorize_predicate(enable) for (signed char g = 1; g < (char)d; g += 3) { a = f[g] ? c : 0; b[g] = 0; } } ``` crashes for me with -mcpu=grace -O3 -msve-vector-bits=128: error in backend: Cannot scalarize scalable vector loads

[davemgreen]

It looks like an extract of a bitcast is expanded via the stack (which itself doesn't need sve-vector-bits) https://clang.godbolt.org/z/j81czfxjc