llvm-project

8a9921f5 - [AArch64] Use INDEX for constant Neon step vectors (#113424)

[AArch64] Use INDEX for constant Neon step vectors (#113424) When compiling for an SVE target we can use INDEX to generate constant fixed-length step vectors, e.g.: ``` uint32x4_t foo() { return (uint32x4_t){0, 1, 2, 3}; } ``` Currently: ``` foo(): adrp x8, .LCPI1_0 ldr q0, [x8, :lo12:.LCPI1_0] ret ``` With INDEX: ``` foo(): index z0.s, #0, #1 ret ``` The logic for this was already in `LowerBUILD_VECTOR`, though it was hidden under a check for `!Subtarget->isNeonAvailable()`. This patch refactors this to enable the corresponding code path unconditionally for constant step vectors (as long as we can use SVE for them).