[llvm] [AMDGPU] Add MachineVerifier check to detect illegal copies from vector register to SGPR (PR #105494)

[Christudasan Devadasan via llvm-commits]

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@@ -4600,15 +4600,37 @@ static bool isSubRegOf(const SIRegisterInfo &TRI,
          SubReg.getReg() == SuperVec.getReg();
 }
 
+// Verify the illegal copy from vector register to SGPR for generic opcode COPY
+bool SIInstrInfo::verifyCopy(const MachineInstr &MI,
+                             const MachineRegisterInfo &MRI,
+                             StringRef &ErrInfo) const {
+  Register DstReg = MI.getOperand(0).getReg();
+  Register SrcReg = MI.getOperand(1).getReg();
+  // This is a check for copy from vector register to SGPR
+  if (RI.isVectorRegister(MRI, SrcReg) && RI.isSGPRReg(MRI, DstReg)) {
+    ErrInfo = "illegal copy from vector register to SGPR";
+    return false;
+  }
+  return true;
+}
+
 bool SIInstrInfo::verifyInstruction(const MachineInstr &MI,
                                     StringRef &ErrInfo) const {
   uint16_t Opcode = MI.getOpcode();
-  if (SIInstrInfo::isGenericOpcode(MI.getOpcode()))
-    return true;
-
   const MachineFunction *MF = MI.getParent()->getParent();
   const MachineRegisterInfo &MRI = MF->getRegInfo();
 
+  // FIXME: At this point the COPY verify is done only for non-ssa forms.
+  // Find a better property to recognize the point where instruction selection
+  // is just done.
+  // We can only enforce this check after SIFixSGPRCopies pass.
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cdevadas wrote:

The last sentence is incomplete. May be, something like the following:
We can only enforce this check after SIFixSGPRCopies so that the illegal copies are legalized and thereafter we don't expect a pass inserting similar copies.

https://github.com/llvm/llvm-project/pull/105494