Replace PROLOG_LABEL with a new CFI_INSTRUCTION.

The old system was fairly convoluted:
* A temporary label was created.
* A single PROLOG_LABEL was created with it.
* A few MCCFIInstructions were created with the same label.

The semantics were that the cfi instructions were mapped to the PROLOG_LABEL
via the temporary label. The output position was that of the PROLOG_LABEL.
The temporary label itself was used only for doing the mapping.

The new CFI_INSTRUCTION has a 1:1 mapping to MCCFIInstructions and points to
one by holding an index into the CFI instructions of this function.

I did consider removing MMI.getFrameInstructions completelly and having
CFI_INSTRUCTION own a MCCFIInstruction, but MCCFIInstructions have non
trivial constructors and destructors and are somewhat big, so the this setup
is probably better.

The net result is that we don't create temporary labels that are never used.

llvm-svn: 203204

1 files changed, 9 insertions, 2 deletions

diff --git a/llvm/lib/CodeGen/MachineInstr.cpp b/llvm/lib/CodeGen/MachineInstr.cpp
index b8f8e703c69..4f0213299aa 100644
--- a/llvm/lib/CodeGen/MachineInstr.cpp
+++ b/llvm/lib/CodeGen/MachineInstr.cpp
@@ -203,6 +203,8 @@ bool MachineOperand::isIdenticalTo(const MachineOperand &Other) const {
     return getRegMask() == Other.getRegMask();
   case MachineOperand::MO_MCSymbol:
     return getMCSymbol() == Other.getMCSymbol();
+  case MachineOperand::MO_CFIIndex:
+    return getCFIIndex() == Other.getCFIIndex();
   case MachineOperand::MO_Metadata:
     return getMetadata() == Other.getMetadata();
   }
@@ -247,6 +249,8 @@ hash_code llvm::hash_value(const MachineOperand &MO) {
     return hash_combine(MO.getType(), MO.getTargetFlags(), MO.getMetadata());
   case MachineOperand::MO_MCSymbol:
     return hash_combine(MO.getType(), MO.getTargetFlags(), MO.getMCSymbol());
+  case MachineOperand::MO_CFIIndex:
+    return hash_combine(MO.getType(), MO.getTargetFlags(), MO.getCFIIndex());
   }
   llvm_unreachable("Invalid machine operand type");
 }
@@ -380,6 +384,9 @@ void MachineOperand::print(raw_ostream &OS, const TargetMachine *TM) const {
   case MachineOperand::MO_MCSymbol:
     OS << "<MCSym=" << *getMCSymbol() << '>';
     break;
+  case MachineOperand::MO_CFIIndex:
+    OS << "<call frame instruction>";
+    break;
   }
 
   if (unsigned TF = getTargetFlags())
@@ -1295,8 +1302,8 @@ bool MachineInstr::isSafeToMove(const TargetInstrInfo *TII,
     return false;
   }
 
-  if (isLabel() || isDebugValue() ||
-      isTerminator() || hasUnmodeledSideEffects())
+  if (isPosition() || isDebugValue() || isTerminator() ||
+      hasUnmodeledSideEffects())
     return false;
 
   // See if this instruction does a load.  If so, we have to guarantee that the