[DebugInfo] Update MachineInstr to help support variadic DBG_VALUE instructions

Following on from this RFC[0] from a while back, this is the first patch towards
implementing variadic debug values.

This patch specifically adds a set of functions to MachineInstr for performing
operations specific to debug values, and replacing uses of the more general
functions where appropriate. The most prevalent of these is replacing
getOperand(0) with getDebugOperand(0) for debug-value-specific code, as the
operands corresponding to values will no longer be at index 0, but index 2 and
upwards: getDebugOperand(x) == getOperand(x+2). Similar replacements have been
added for the other operands, along with some helper functions to replace
oft-repeated code and operate on a variable number of value operands.

[0] http://lists.llvm.org/pipermail/llvm-dev/2020-February/139376.html<Paste>

Differential Revision: https://reviews.llvm.org/D81852

1 files changed, 20 insertions, 18 deletions

diff --git a/llvm/lib/CodeGen/LiveDebugValues.cpp b/llvm/lib/CodeGen/LiveDebugValues.cpp
index c4b551e..b487ccb 100644
--- a/llvm/lib/CodeGen/LiveDebugValues.cpp
+++ b/llvm/lib/CodeGen/LiveDebugValues.cpp
@@ -174,7 +174,8 @@ static Register isDbgValueDescribedByReg(const MachineInstr &MI) {
   assert(MI.getNumOperands() == 4 && "malformed DBG_VALUE");
   // If location of variable is described using a register (directly
   // or indirectly), this register is always a first operand.
-  return MI.getOperand(0).isReg() ? MI.getOperand(0).getReg() : Register();
+  return MI.getDebugOperand(0).isReg() ? MI.getDebugOperand(0).getReg()
+                                       : Register();
 }
 
 /// If \p Op is a stack or frame register return true, otherwise return false.
@@ -334,15 +335,15 @@ private:
       if (int RegNo = isDbgValueDescribedByReg(MI)) {
         Kind = RegisterKind;
         Loc.RegNo = RegNo;
-      } else if (MI.getOperand(0).isImm()) {
+      } else if (MI.getDebugOperand(0).isImm()) {
         Kind = ImmediateKind;
-        Loc.Immediate = MI.getOperand(0).getImm();
-      } else if (MI.getOperand(0).isFPImm()) {
+        Loc.Immediate = MI.getDebugOperand(0).getImm();
+      } else if (MI.getDebugOperand(0).isFPImm()) {
         Kind = ImmediateKind;
-        Loc.FPImm = MI.getOperand(0).getFPImm();
-      } else if (MI.getOperand(0).isCImm()) {
+        Loc.FPImm = MI.getDebugOperand(0).getFPImm();
+      } else if (MI.getDebugOperand(0).isCImm()) {
         Kind = ImmediateKind;
-        Loc.CImm = MI.getOperand(0).getCImm();
+        Loc.CImm = MI.getDebugOperand(0).getCImm();
       }
 
       // We create the debug entry values from the factory functions rather than
@@ -430,8 +431,8 @@ private:
         // expression. The register location of such DBG_VALUE is always the one
         // from the entry DBG_VALUE, it does not matter if the entry value was
         // copied in to another register due to some optimizations.
-        return BuildMI(MF, DbgLoc, IID, Indirect, MI.getOperand(0).getReg(),
-                       Var, Expr);
+        return BuildMI(MF, DbgLoc, IID, Indirect,
+                       MI.getDebugOperand(0).getReg(), Var, Expr);
       case RegisterKind:
         // Register locations are like the source DBG_VALUE, but with the
         // register number from this VarLoc.
@@ -447,7 +448,7 @@ private:
         return BuildMI(MF, DbgLoc, IID, true, Base, Var, SpillExpr);
       }
       case ImmediateKind: {
-        MachineOperand MO = MI.getOperand(0);
+        MachineOperand MO = MI.getDebugOperand(0);
         return BuildMI(MF, DbgLoc, IID, Indirect, MO, Var, DIExpr);
       }
       case EntryValueBackupKind:
@@ -1020,7 +1021,7 @@ bool LiveDebugValues::removeEntryValue(const MachineInstr &MI,
   // the entry value any more. In addition, if the debug expression from the
   // DBG_VALUE is not empty, we can assume the parameter's value has changed
   // indicating that we should stop tracking its entry value as well.
-  if (!MI.getOperand(0).isReg() ||
+  if (!MI.getDebugOperand(0).isReg() ||
       MI.getDebugExpression()->getNumElements() != 0)
     return true;
 
@@ -1028,7 +1029,7 @@ bool LiveDebugValues::removeEntryValue(const MachineInstr &MI,
   // it means the parameter's value has not changed and we should be able to use
   // its entry value.
   bool TrySalvageEntryValue = false;
-  Register Reg = MI.getOperand(0).getReg();
+  Register Reg = MI.getDebugOperand(0).getReg();
   auto I = std::next(MI.getReverseIterator());
   const MachineOperand *SrcRegOp, *DestRegOp;
   if (I != MI.getParent()->rend()) {
@@ -1050,7 +1051,7 @@ bool LiveDebugValues::removeEntryValue(const MachineInstr &MI,
     for (uint64_t ID : OpenRanges.getEntryValueBackupVarLocs()) {
       const VarLoc &VL = VarLocIDs[LocIndex::fromRawInteger(ID)];
       if (VL.getEntryValueCopyBackupReg() == Reg &&
-          VL.MI.getOperand(0).getReg() == SrcRegOp->getReg())
+          VL.MI.getDebugOperand(0).getReg() == SrcRegOp->getReg())
         return false;
     }
   }
@@ -1088,8 +1089,8 @@ void LiveDebugValues::transferDebugValue(const MachineInstr &MI,
     }
   }
 
-  if (isDbgValueDescribedByReg(MI) || MI.getOperand(0).isImm() ||
-      MI.getOperand(0).isFPImm() || MI.getOperand(0).isCImm()) {
+  if (isDbgValueDescribedByReg(MI) || MI.getDebugOperand(0).isImm() ||
+      MI.getDebugOperand(0).isFPImm() || MI.getDebugOperand(0).isCImm()) {
     // Use normal VarLoc constructor for registers and immediates.
     VarLoc VL(MI, LS);
     // End all previous ranges of VL.Var.
@@ -1102,7 +1103,8 @@ void LiveDebugValues::transferDebugValue(const MachineInstr &MI,
     llvm_unreachable("DBG_VALUE with mem operand encountered after regalloc?");
   } else {
     // This must be an undefined location. If it has an open range, erase it.
-    assert(MI.getOperand(0).isReg() && MI.getOperand(0).getReg() == 0 &&
+    assert(MI.getDebugOperand(0).isReg() &&
+           MI.getDebugOperand(0).getReg() == 0 &&
            "Unexpected non-undef DBG_VALUE encountered");
     VarLoc VL(MI, LS);
     OpenRanges.erase(VL);
@@ -1738,14 +1740,14 @@ bool LiveDebugValues::isEntryValueCandidate(
   // Only consider parameters that are described using registers. Parameters
   // that are passed on the stack are not yet supported, so ignore debug
   // values that are described by the frame or stack pointer.
-  if (!isRegOtherThanSPAndFP(MI.getOperand(0), MI, TRI))
+  if (!isRegOtherThanSPAndFP(MI.getDebugOperand(0), MI, TRI))
     return false;
 
   // If a parameter's value has been propagated from the caller, then the
   // parameter's DBG_VALUE may be described using a register defined by some
   // instruction in the entry block, in which case we shouldn't create an
   // entry value.
-  if (DefinedRegs.count(MI.getOperand(0).getReg()))
+  if (DefinedRegs.count(MI.getDebugOperand(0).getReg()))
     return false;
 
   // TODO: Add support for parameters that have a pre-existing debug expressions