AMDGPU: Permit more frame index operands in verifier (llvm#101691)

Treat FI operands more like a register. When it gets materialized,
we will typically need to introduce a scavenged register anyway.
Add baseline tests for folding frame indexes into add/or.

Author: arsenm

llvm/lib/Target/AMDGPU/SIInstrInfo.cpp

@@ -4665,6 +4665,10 @@ static bool shouldReadExec(const MachineInstr &MI) {
   return true;
 }
 
+static bool isRegOrFI(const MachineOperand &MO) {
+  return MO.isReg() || MO.isFI();
+}
+
 static bool isSubRegOf(const SIRegisterInfo &TRI,
                        const MachineOperand &SuperVec,
                        const MachineOperand &SubReg) {
@@ -4999,7 +5003,7 @@ bool SIInstrInfo::verifyInstruction(const MachineInstr &MI,
             ++ConstantBusCount;
             SGPRsUsed.push_back(SGPRUsed);
           }
-        } else {
+        } else if (!MO.isFI()) { // Treat FI like a register.
           if (!UsesLiteral) {
             ++ConstantBusCount;
             UsesLiteral = true;
@@ -5092,7 +5096,7 @@ bool SIInstrInfo::verifyInstruction(const MachineInstr &MI,
     const MachineOperand &Src0 = MI.getOperand(Src0Idx);
     const MachineOperand &Src1 = MI.getOperand(Src1Idx);
 
-    if (!Src0.isReg() && !Src1.isReg() &&
+    if (!isRegOrFI(Src0) && !isRegOrFI(Src1) &&
         !isInlineConstant(Src0, Desc.operands()[Src0Idx]) &&
         !isInlineConstant(Src1, Desc.operands()[Src1Idx]) &&
         !Src0.isIdenticalTo(Src1)) {