[llvm] [LICM] Hoisting writeonly calls (PR #143799)

[Jiachen Wang via llvm-commits]

WanderingAura wrote:

It looks like a writeonly function is getting hoisting in CodeGen/AMDGPU/loop_exit_with_xor.ll and I'm not sure if it's incorrect behaviour.
https://github.com/llvm/llvm-project/blob/267b859fc60acda510027bd6139c54d660c6fb21/llvm/test/CodeGen/AMDGPU/loop_exit_with_xor.ll#L59-L93

The call @llvm.amdgcn.raw.ptr.buffer.store.f32(float poison, ptr addrspace(8) poison, i32 0, i32 poison, i32 0) seems to be getting hoisted. Does anyone know if this is legal behaviour?

Below is the failed CI logs:
```
2025-06-16T08:20:15.7502444Z Check file: /home/gha/actions-runner/_work/llvm-project/llvm-project/llvm/test/CodeGen/AMDGPU/loop_exit_with_xor.ll
2025-06-16T08:20:15.7503881Z 
2025-06-16T08:20:15.7504165Z -dump-input=help explains the following input dump.
2025-06-16T08:20:15.7504657Z 
2025-06-16T08:20:15.7504821Z Input was:
2025-06-16T08:20:15.7505247Z <<<<<<
2025-06-16T08:20:15.7505624Z          .
2025-06-16T08:20:15.7506041Z          .
2025-06-16T08:20:15.7506423Z          .
2025-06-16T08:20:15.7506833Z         57:  .type doesnt_need_and, at function 
2025-06-16T08:20:15.7507493Z         58: doesnt_need_and: ; @doesnt_need_and 
2025-06-16T08:20:15.7508167Z         59: ; %bb.0: ; %entry 
2025-06-16T08:20:15.7509005Z         60:  s_waitcnt vmcnt(0) expcnt(0) lgkmcnt(0) 
2025-06-16T08:20:15.7509683Z         61:  buffer_store_dword v0, off, s[4:7], s4 
2025-06-16T08:20:15.7510378Z         62:  s_mov_b32 s6, 0 
2025-06-16T08:20:15.7511008Z next:67      !~~~~~~~~~~~~~~  error: match on wrong line
2025-06-16T08:20:15.7511636Z         63:  s_mov_b64 s[4:5], 0 
2025-06-16T08:20:15.7512474Z         64: .LBB1_1: ; %loop 
2025-06-16T08:20:15.7513130Z         65:  ; =>This Inner Loop Header: Depth=1 
2025-06-16T08:20:15.7513783Z         66:  s_add_i32 s6, s6, 1 
2025-06-16T08:20:15.7514405Z         67:  v_cmp_le_u32_e32 vcc, s6, v0 
2025-06-16T08:20:15.7515002Z          .
2025-06-16T08:20:15.7515394Z          .
2025-06-16T08:20:15.7515781Z          .
2025-06-16T08:20:15.7516173Z >>>>>>
```



https://github.com/llvm/llvm-project/pull/143799