[llvm] [AMDGPU] Do not bother adding reserved registers to liveins (PR #79436)

[Jay Foad via llvm-commits]

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@@ -6890,11 +6890,9 @@ bool AMDGPULegalizerInfo::legalizeWaveID(MachineInstr &MI,
     return false;
   LLT S32 = LLT::scalar(32);
   Register DstReg = MI.getOperand(0).getReg();
-  Register TTMP8 =
-      getFunctionLiveInPhysReg(B.getMF(), B.getTII(), AMDGPU::TTMP8,
-                               AMDGPU::SReg_32RegClass, B.getDebugLoc(), S32);
   auto LSB = B.buildConstant(S32, 25);
   auto Width = B.buildConstant(S32, 5);
+  auto TTMP8 = B.buildCopy(S32, Register(AMDGPU::TTMP8));
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jayfoad wrote:

This will build the copy here instead of in the entry block, and will create a new one for each use of the intrinsic. Is that OK?

https://github.com/llvm/llvm-project/pull/79436