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, 8 insertions, 17 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
index 7e0b2f4af2e..50161c5af97 100644
--- a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
@@ -699,9 +699,7 @@ bool AsmPrinter::needsSEHMoves() {
     MF->getFunction()->needsUnwindTableEntry();
 }
 
-void AsmPrinter::emitPrologLabel(const MachineInstr &MI) {
-  const MCSymbol *Label = MI.getOperand(0).getMCSymbol();
-
+void AsmPrinter::emitCFIInstruction(const MachineInstr &MI) {
   ExceptionHandling::ExceptionsType ExceptionHandlingType =
       MAI->getExceptionHandlingType();
   if (ExceptionHandlingType != ExceptionHandling::DwarfCFI &&
@@ -716,16 +714,9 @@ void AsmPrinter::emitPrologLabel(const MachineInstr &MI) {
 
   const MachineModuleInfo &MMI = MF->getMMI();
   const std::vector<MCCFIInstruction> &Instrs = MMI.getFrameInstructions();
-  bool FoundOne = false;
-  (void)FoundOne;
-  for (std::vector<MCCFIInstruction>::const_iterator I = Instrs.begin(),
-         E = Instrs.end(); I != E; ++I) {
-    if (I->getLabel() == Label) {
-      emitCFIInstruction(*I);
-      FoundOne = true;
-    }
-  }
-  assert(FoundOne);
+  unsigned CFIIndex = MI.getOperand(0).getCFIIndex();
+  const MCCFIInstruction &CFI = Instrs[CFIIndex];
+  emitCFIInstruction(CFI);
 }
 
 /// EmitFunctionBody - This method emits the body and trailer for a
@@ -748,7 +739,7 @@ void AsmPrinter::EmitFunctionBody() {
       LastMI = II;
 
       // Print the assembly for the instruction.
-      if (!II->isLabel() && !II->isImplicitDef() && !II->isKill() &&
+      if (!II->isPosition() && !II->isImplicitDef() && !II->isKill() &&
           !II->isDebugValue()) {
         HasAnyRealCode = true;
         ++EmittedInsts;
@@ -767,8 +758,8 @@ void AsmPrinter::EmitFunctionBody() {
         emitComments(*II, OutStreamer.GetCommentOS());
 
       switch (II->getOpcode()) {
-      case TargetOpcode::PROLOG_LABEL:
-        emitPrologLabel(*II);
+      case TargetOpcode::CFI_INSTRUCTION:
+        emitCFIInstruction(*II);
         break;
 
       case TargetOpcode::EH_LABEL:
@@ -811,7 +802,7 @@ void AsmPrinter::EmitFunctionBody() {
   // label equaling the end of function label and an invalid "row" in the
   // FDE. We need to emit a noop in this situation so that the FDE's rows are
   // valid.
-  bool RequiresNoop = LastMI && LastMI->isPrologLabel();
+  bool RequiresNoop = LastMI && LastMI->isCFIInstruction();
 
   // If the function is empty and the object file uses .subsections_via_symbols,
   // then we need to emit *something* to the function body to prevent the