[CodeGen][MachineVerifier] Use TypeSize instead of unsigned for getRegSizeInBits

This patch changes getRegSizeInBits to return a TypeSize instead of an
unsigned in the case that a virtual register has a scalable LLT. In the
case that register is physical, a Fixed TypeSize is returned.

The MachineVerifier pass is updated to allow copies between fixed and
scalable operands as long as the Src size will fit into the Dest size.

This is a precommit which will be stacked on by a change to GISel to
generate COPYs with a scalable destination but a fixed size source.

Author: michaelmaitland

llvm/include/llvm/CodeGen/TargetRegisterInfo.h

@@ -283,8 +283,8 @@ class TargetRegisterInfo : public MCRegisterInfo {
   // DenseMapInfo<unsigned> uses -1u and -2u.
 
   /// Return the size in bits of a register from class RC.
-  unsigned getRegSizeInBits(const TargetRegisterClass &RC) const {
-    return getRegClassInfo(RC).RegSize;
+  TypeSize getRegSizeInBits(const TargetRegisterClass &RC) const {
+    return TypeSize::Fixed(getRegClassInfo(RC).RegSize);
   }
 
   /// Return the size in bytes of the stack slot allocated to hold a spilled
@@ -858,7 +858,7 @@ class TargetRegisterInfo : public MCRegisterInfo {
     const TargetRegisterClass *RC) const = 0;
 
   /// Returns size in bits of a phys/virtual/generic register.
-  unsigned getRegSizeInBits(Register Reg, const MachineRegisterInfo &MRI) const;
+  TypeSize getRegSizeInBits(Register Reg, const MachineRegisterInfo &MRI) const;
 
   /// Get the weight in units of pressure for this register unit.
   virtual unsigned getRegUnitWeight(unsigned RegUnit) const = 0;

llvm/lib/CodeGen/MachineVerifier.cpp

@@ -1937,16 +1937,17 @@ void MachineVerifier::visitMachineInstrBefore(const MachineInstr *MI) {
 
     // If we have only one valid type, this is likely a copy between a virtual
     // and physical register.
-    unsigned SrcSize = 0;
-    unsigned DstSize = 0;
+    TypeSize SrcSize = TRI->getRegSizeInBits(SrcReg, *MRI);
+    TypeSize DstSize = TRI->getRegSizeInBits(DstReg, *MRI);
+
     if (SrcReg.isPhysical() && DstTy.isValid()) {
       const TargetRegisterClass *SrcRC =
           TRI->getMinimalPhysRegClassLLT(SrcReg, DstTy);
       if (SrcRC)
         SrcSize = TRI->getRegSizeInBits(*SrcRC);
     }
 
-    if (SrcSize == 0)
+    if (SrcSize.isZero())
       SrcSize = TRI->getRegSizeInBits(SrcReg, *MRI);
 
     if (DstReg.isPhysical() && SrcTy.isValid()) {
@@ -1956,10 +1957,21 @@ void MachineVerifier::visitMachineInstrBefore(const MachineInstr *MI) {
         DstSize = TRI->getRegSizeInBits(*DstRC);
     }
 
-    if (DstSize == 0)
+    if (DstSize.isZero())
       DstSize = TRI->getRegSizeInBits(DstReg, *MRI);
 
-    if (SrcSize != 0 && DstSize != 0 && SrcSize != DstSize) {
+    // If the Dst is scalable and the Src is fixed, then the Dst can only hold
+    // the Src if the minimum size Dst can hold is at least as big as Src.
+    if (DstSize.isScalable() && !SrcSize.isScalable() &&
+        DstSize.getKnownMinValue() <= SrcSize.getFixedValue())
+      break;
+    // If the Src is scalable and the Dst is fixed, then Dest can only hold
+    // the Src is known to fit in Dest
+    if (SrcSize.isScalable() && !DstSize.isScalable() &&
+        TypeSize::isKnownLE(DstSize, SrcSize))
+      break;
+
+    if (SrcSize.isNonZero() && DstSize.isNonZero() && SrcSize != DstSize) {
       if (!DstOp.getSubReg() && !SrcOp.getSubReg()) {
         report("Copy Instruction is illegal with mismatching sizes", MI);
         errs() << "Def Size = " << DstSize << ", Src Size = " << SrcSize

llvm/lib/CodeGen/TargetRegisterInfo.cpp

@@ -499,7 +499,7 @@ bool TargetRegisterInfo::regmaskSubsetEqual(const uint32_t *mask0,
   return true;
 }
 
-unsigned
+TypeSize
 TargetRegisterInfo::getRegSizeInBits(Register Reg,
                                      const MachineRegisterInfo &MRI) const {
   const TargetRegisterClass *RC{};
@@ -508,16 +508,15 @@ TargetRegisterInfo::getRegSizeInBits(Register Reg,
     // Instead, we need to access a register class that contains Reg and
     // get the size of that register class.
     RC = getMinimalPhysRegClass(Reg);
-  } else {
-    LLT Ty = MRI.getType(Reg);
-    unsigned RegSize = Ty.isValid() ? Ty.getSizeInBits() : 0;
-    // If Reg is not a generic register, query the register class to
-    // get its size.
-    if (RegSize)
-      return RegSize;
-    // Since Reg is not a generic register, it must have a register class.
-    RC = MRI.getRegClass(Reg);
+    assert(RC && "Unable to deduce the register class");
+    return getRegSizeInBits(*RC);
   }
+  LLT Ty = MRI.getType(Reg);
+  if (Ty.isValid())
+    return Ty.getSizeInBits();
+
+  // Since Reg is not a generic register, it may have a register class.
+  RC = MRI.getRegClass(Reg);
   assert(RC && "Unable to deduce the register class");
   return getRegSizeInBits(*RC);
 }