[all-commits] [llvm/llvm-project] 208edf: [RISCV] Fix assertion in lowerEXTRACT_SUBVECTOR

[Luke Lau via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 208edf7672cd2e84ae5da4df423adccd752ee1f1
      https://github.com/llvm/llvm-project/commit/208edf7672cd2e84ae5da4df423adccd752ee1f1
  Author: Luke Lau <luke at igalia.com>
  Date:   2024-02-13 (Tue, 13 Feb 2024)

  Changed paths:
    M llvm/lib/Target/RISCV/RISCVISelLowering.cpp
    M llvm/test/CodeGen/RISCV/rvv/fixed-vectors-extract-subvector.ll

  Log Message:
  -----------
  [RISCV] Fix assertion in lowerEXTRACT_SUBVECTOR

This fixes a crash when lowering an extract_subvector like:

t0:v1i64 = extract_subvector t1:v2i64, 1

Whilst we never need a vslidedown with M1 on scalable vector types, we might
need to do it for v1i64/v1f64, since the smallest container type for it is
nxv1i64/nxv1f64.

The lowering code is still correct for this case, but the assertion was too
strict. The actual invariant we're relying on is that ContainerSubVecVT's LMUL
<= M1, not < M1. Hence why we handled v2i32 fine, because its container type
was nxv1i32 and MF2.