The Clang compiler, LLVM reports error "fatal error: error in backend: Invalid size request on a scalable vector." starting from version 17.0.1 with the following compiler options:

-march=armv9-a and higher (armv9.1-a, armv9.2-a, armv9.3-a and so on) and -mstrict-align and optimization flags like -Os, -O2

Notes when it works successfully:

• When Optimization flag: -O0, -O1, -O3, example https://gcc.godbolt.org/z/4ojzoz9jP
• Without -mstrict-align flag, example https://gcc.godbolt.org/z/7MbqGfoe8
• Without any optimization flags and specified -mstrict-align with -march=armv9-a, example https://gcc.godbolt.org/z/e7q1bv498
• When target architecture from armv8-a to armv8.9-a, example https://gcc.godbolt.org/z/q6eobPPPx
• When loop iteration count not power of 2, for example, array_size is 127 - https://gcc.godbolt.org/z/d7rKvdboG

armv8-a clang (trunk) - Failed

• https://gcc.godbolt.org/z/9r5Mva8oe

armv8-a clang 18.1.0 - Failed

• https://gcc.godbolt.org/z/747e3hd7h

armv8-a clang 17.0.1 - Failed

• https://gcc.godbolt.org/z/zMW4hWGhW

armv8-a clang 16.0.0 - No problem

• https://gcc.godbolt.org/z/nr9a9EhM5

Steps to reproduce the issue.

#include<stdint.h>#include<stdlib.h>uint64_t*InvalidSizeRequestOnScalableVector() { uint64_tvalue=30; uint64_tarray_size=128; uint64_t*array= (uint64_t*) malloc(sizeof(uint64_t) *array_size); for (unsigned longi=0; i<array_size; i++) { array[i] =value; } returnarray; }