[llvm] [AMDGPU] In instruction selector, allow copy from physical reg to s1 (PR #96157)

[Jun Wang via llvm-commits]

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@@ -138,6 +138,10 @@ bool AMDGPUInstructionSelector::selectCOPY(MachineInstr &I) const {
       return RBI.constrainGenericRegister(DstReg, *RC, *MRI);
     }
 
+    // Allow copy from physical register other than SCC to s1.
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jwanggit86 wrote:

This is inside an IF stmt that calls `isVCC` on the dst reg. But `isVCC` may be true for other regs than VCC?

https://github.com/llvm/llvm-project/pull/96157