<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/114482>114482</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [SPIR-V] Reg2Mem producing unwanted bitcast
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            new issue
      </td>
    </tr>

    <tr>
      <th>Assignees</th>
      <td>
      </td>
    </tr>

    <tr>
      <th>Reporter</th>
      <td>
          spall
      </td>
    </tr>
</table>

<pre>
    It seems enabling reg2mem here ( #111026  ) has introduced what looks like a bug, when doing SPIRV codegen.  What looks like an unnecessary bitcast is generated.  See %9: 
```llvm
    %1 = OpTypeFloat 32
    %2 = OpTypeFunction %1 %1
    %3 = OpTypeInt 32 0
    %4 = OpConstant %3 0
    %5 = OpConstant %1 0
    %6 = OpConstant %1 1
    %8 = OpFunction %1 None %2              ; -- Begin function saturate_float
    %7 = OpFunctionParameter %1
    %12 = OpLabel
    %9 = OpBitcast %3 %4
    %10 = OpExtInst %1 %11 FClamp %7 %5 %6
    OpReturnValue %10
 OpFunctionEnd
```
saturate-repro.ll : 
```llvm
; this was just taken from the
; llvm/CodeGen/SPIRV/hlsl-intrinsics/saturate.ll test cases.

define noundef float @saturate_float(float noundef %a) {
entry:
  %hlsl.saturate = call float @llvm.spv.saturate.f32(float %a)
  ret float %hlsl.saturate
}
```
To reproduce this issue:
-  build main branch llvm
 - cmake command used:
 ```
 cmake -G Ninja -DCMAKE_BUILD_TYPE=RelWithDebInfo -C <your-path>/llvm-project/clang/cmake/caches/HLSL.cmake -DLLVM_ENABLE_ASSERTIONS=On -DCMAKE_CXX_COMPILER=/usr/bin/clang++ -DCMAKE_C_COMPILER=/usr/bin/clang -DLLVM_USE_LINKER=lld ../llvm
 ```
- run test provided above. 
```
 llc -verify-machineinstrs -O0 -mtriple=spirv-unknown-unknown saturate-repro.ll -o -
```

note: this bitcast seemingly appears in all the CodeGen/SPIRV/hlsl-intrinsics tests.
note: Also see comment I left on #111026 
</pre>
<img width="1px" height="1px" alt="" src="http://email.email.llvm.org/o/eJyEVltv4joX_TXmZStR4hAKDzwAgfnQ0ItKpzPfE3KSTeKpY0e2Qw___si5lIFWZ6oqEXjtta_LG2YMLyTinMRLEicj1thS6bmpmRCjVOXn-daCQawMoGSp4LIAjQWtsIISNQKhUyA0CsMwoBMAQmdQMgNcWq3yJsMc3ktmQSj1ZkDwNwQGaVMQuoL3EiXkylHun7bPr5CpHAuUPsDPWxsJjZSYoTFMnyHlNmPGAjdQoETNLOY-wB5dPPGMRAsgQUKCBZkE3b8Qp6r7CsBFGYdAogQe65dzjRuhmIWIXgHon4BGZpYr2RvSOLyCRn9At9IxQXAFGPeAlZLGMmk7o2tM_AUmvMFMvsRcBzPtMdcxPyiJXVZXfyRagufBEgsu4ThYGGYbV9PD0RXmiv3uhv2JaVahRf25KuFQwR1LUVwdzfqTZd_HroY0Hl8TBD1s_Y_dSmMv1Q9hsxKsqvuI2uLReHKxfqyf0TZavjLRYMfVH15CX8v8Zki6j0P2nsZaK18I-M95ciW0JTfwzgz8bowFy95QwlGrCmyJF1RrQzcrleM3lIRu2qkndFMKIzynGC4NzwyhmyEG592isZAxg8bvudpnjkcuEaRqZI5HaFsFZBzcNI9Ou5MBR2jMnEjJ3bLjQWn1mUSLoXiExi4ef-Bpe5AxIS4uXCK-qU8fGP8Y0Q9PvYeBT6OFj4Mr5j6bu-TLNrwoaBvgLpGuwNyYBj8i9QDShoscKsYlpJrJrIQ_ZO5BVrE3hExVFZM5NAbzS5o3znqs9w0euPzNwEtW94vv68Pyx3aXHF7-_7QmUfKM4ie3ZYLpVh4VeCsg0eqsGu3VzJYkWhO6cQF4tVa_MbOEbjLBZOHejt69WVaia_D_dvud3ztNdrvX-8P6YbHcrQ-L_X79_LJ9fNiTKHmUH5Gsfv06rB7vn7a79TOJEkI3jdGEblIuL36WhC4vFn_DD55_7NeH3fbhewsUIgff7zP5ulge6EZ2Y1lrdeI55sBSdUL_ViW9vRAZeCfU_Hj2KpaVXCKXxmoD3mMAXmU1rwWSKDE11yevkW9SvcvhDZ8F6SnwvnTVPaWybk66qRl2hVtiXBbiDKyukWm3o8CNtS0R_qrJNt1BgAP_QhjleNsZQ2lhCwKPFtpLd1iJo3we5bNoxkY4D--iYBzGYzodlfNwEuAxyOl4NgnTFGczlmI4w8kMWR5nGY74nAZ0HAZRSGl8F0z9WR7F0ywexxOWxRRDMg6wYlz4rSCVLkatROZhOB5P6Ui4e9e0m51Sie-9gCh1i17P21FNm8I4RXOX3QeN5Va0PwlcNbxXEifwjAW9xwo6Rbqd3ch3Ji3mQ4VHjRbz0traOJnRDaGbgtuySf1MVcNAfVJIG5NTRB_0aU7_DQAA__8hmo3o">