AMDGPU: Fixes for regbankselecting copies of i1 physregs to sgprs (#159283)

If the source register of a copy was a physical sgpr copied to an
s1 value, this would assert.

Author: arsenm

llvm/lib/Target/AMDGPU/AMDGPURegisterBankInfo.cpp

@@ -3845,21 +3845,27 @@ AMDGPURegisterBankInfo::getInstrMapping(const MachineInstr &MI) const {
     // want the most straightforward mapping, so just directly handle this.
     const RegisterBank *DstBank = getRegBank(DstReg, MRI, *TRI);
     const RegisterBank *SrcBank = getRegBank(SrcReg, MRI, *TRI);
-    assert(SrcBank && "src bank should have been assigned already");
 
     // For COPY between a physical reg and an s1, there is no type associated so
     // we need to take the virtual register's type as a hint on how to interpret
     // s1 values.
+    unsigned Size;
     if (!SrcReg.isVirtual() && !DstBank &&
-        MRI.getType(DstReg) == LLT::scalar(1))
+        MRI.getType(DstReg) == LLT::scalar(1)) {
       DstBank = &AMDGPU::VCCRegBank;
-    else if (!DstReg.isVirtual() && MRI.getType(SrcReg) == LLT::scalar(1))
+      Size = 1;
+    } else if (!DstReg.isVirtual() && MRI.getType(SrcReg) == LLT::scalar(1)) {
       DstBank = &AMDGPU::VCCRegBank;
+      Size = 1;
+    } else {
+      Size = getSizeInBits(DstReg, MRI, *TRI);
+    }
 
     if (!DstBank)
       DstBank = SrcBank;
+    else if (!SrcBank)
+      SrcBank = DstBank;
 
-    unsigned Size = getSizeInBits(DstReg, MRI, *TRI);
     if (MI.getOpcode() != AMDGPU::G_FREEZE &&
         cannotCopy(*DstBank, *SrcBank, TypeSize::getFixed(Size)))
       return getInvalidInstructionMapping();