[llvm] [MachineVerifier] Query TargetInstrInfo for PHI nodes. (PR #110507)

[Nathan Gauër via llvm-commits]

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@@ -2278,6 +2278,32 @@ class TargetInstrInfo : public MCInstrInfo {
     llvm_unreachable("unknown number of operands necessary");
   }
 
+  // This this instruction a PHI node.
+  // This function should be favored over MI.isPHI() as it allows backends to
+  // define additional PHI instructions.
+  virtual bool isPhiInstr(const MachineInstr &MI) const {
+    return MI.getOpcode() == TargetOpcode::G_PHI ||
+           MI.getOpcode() == TargetOpcode::PHI;
+  }
+
+  // Returns the number of [Value, Src] pairs this phi instruction has.
+  // Only valid to call on a phi node.
+  virtual unsigned getNumPhiIncomingPair(const MachineInstr &MI) const {
+    assert(isPhiInstr(MI));
+    // G_PHI/PHI only have a single operand before the pairs. 2 Operands per
+    // pair.
+    return (MI.getNumOperands() - 1) / 2;
+  }
+
+  // Returns the |index|'th [Value, Src] pair of this phi instruction.
+  virtual std::pair<MachineOperand, MachineBasicBlock *>
+  getPhiIncomingPair(const MachineInstr &MI, unsigned index) const {
+    // Behavior for G_PHI/PHI instructions.
+    MachineOperand Operand = MI.getOperand(index * 2 + 1);
+    MachineBasicBlock *MBB = MI.getOperand(index * 2 + 2).getMBB();
+    return {Operand, MBB};
+  }
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Keenuts wrote:

> I meant tests that hit the error in test/MachineVerifier, not tests that you are trying to make not fail the verifier

Added a new MachineVerifer test: `llvm/test/MachineVerifier/verifier-phi-spirv.mir`

https://github.com/llvm/llvm-project/pull/110507