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, 50 insertions, 53 deletions

diff --git a/llvm/lib/Target/ARM/ARMFrameLowering.cpp b/llvm/lib/Target/ARM/ARMFrameLowering.cpp
index 274a125126a..c35cd23b91c 100644
--- a/llvm/lib/Target/ARM/ARMFrameLowering.cpp
+++ b/llvm/lib/Target/ARM/ARMFrameLowering.cpp
@@ -179,24 +179,22 @@ void ARMFrameLowering::emitPrologue(MachineFunction &MF) const {
   if (ArgRegsSaveSize) {
     emitSPUpdate(isARM, MBB, MBBI, dl, TII, -ArgRegsSaveSize,
                  MachineInstr::FrameSetup);
-    MCSymbol *SPLabel = Context.CreateTempSymbol();
-    BuildMI(MBB, MBBI, dl, TII.get(TargetOpcode::PROLOG_LABEL))
-        .addSym(SPLabel);
     CFAOffset -= ArgRegsSaveSize;
-    MMI.addFrameInst(
-        MCCFIInstruction::createDefCfaOffset(SPLabel, CFAOffset));
+    unsigned CFIIndex = MMI.addFrameInst(
+        MCCFIInstruction::createDefCfaOffset(nullptr, CFAOffset));
+    BuildMI(MBB, MBBI, dl, TII.get(TargetOpcode::CFI_INSTRUCTION))
+        .addCFIIndex(CFIIndex);
   }
 
   if (!AFI->hasStackFrame()) {
     if (NumBytes - ArgRegsSaveSize != 0) {
       emitSPUpdate(isARM, MBB, MBBI, dl, TII, -(NumBytes - ArgRegsSaveSize),
                    MachineInstr::FrameSetup);
-      MCSymbol *SPLabel = Context.CreateTempSymbol();
-      BuildMI(MBB, MBBI, dl, TII.get(TargetOpcode::PROLOG_LABEL))
-          .addSym(SPLabel);
       CFAOffset -= NumBytes - ArgRegsSaveSize;
-      MMI.addFrameInst(MCCFIInstruction::createDefCfaOffset(SPLabel,
-                                                            CFAOffset));
+      unsigned CFIIndex = MMI.addFrameInst(
+          MCCFIInstruction::createDefCfaOffset(nullptr, CFAOffset));
+      BuildMI(MBB, MBBI, dl, TII.get(TargetOpcode::CFI_INSTRUCTION))
+          .addCFIIndex(CFIIndex);
     }
     return;
   }
@@ -311,12 +309,12 @@ void ARMFrameLowering::emitPrologue(MachineFunction &MF) const {
   }
 
   if (adjustedGPRCS1Size > 0) {
-    MCSymbol *SPLabel = Context.CreateTempSymbol();
-    BuildMI(MBB, ++GPRCS1Push, dl, TII.get(TargetOpcode::PROLOG_LABEL))
-        .addSym(SPLabel);
     CFAOffset -= adjustedGPRCS1Size;
-    MMI.addFrameInst(
-        MCCFIInstruction::createDefCfaOffset(SPLabel, CFAOffset));
+    unsigned CFIIndex = MMI.addFrameInst(
+        MCCFIInstruction::createDefCfaOffset(nullptr, CFAOffset));
+    MachineBasicBlock::iterator Pos = ++GPRCS1Push;
+    BuildMI(MBB, Pos, dl, TII.get(TargetOpcode::CFI_INSTRUCTION))
+        .addCFIIndex(CFIIndex);
     for (std::vector<CalleeSavedInfo>::const_iterator I = CSI.begin(),
            E = CSI.end(); I != E; ++I) {
       unsigned Reg = I->getReg();
@@ -339,9 +337,10 @@ void ARMFrameLowering::emitPrologue(MachineFunction &MF) const {
       case ARM::R6:
       case ARM::R7:
       case ARM::LR:
-        MMI.addFrameInst(MCCFIInstruction::createOffset(SPLabel,
-           MRI->getDwarfRegNum(Reg, true),
-           MFI->getObjectOffset(FI)));
+        CFIIndex = MMI.addFrameInst(MCCFIInstruction::createOffset(
+            nullptr, MRI->getDwarfRegNum(Reg, true), MFI->getObjectOffset(FI)));
+        BuildMI(MBB, Pos, dl, TII.get(TargetOpcode::CFI_INSTRUCTION))
+            .addCFIIndex(CFIIndex);
         break;
       }
     }
@@ -357,28 +356,30 @@ void ARMFrameLowering::emitPrologue(MachineFunction &MF) const {
     emitRegPlusImmediate(!AFI->isThumbFunction(), MBB, GPRCS1Push, dl, TII,
                          FramePtr, ARM::SP, FramePtrOffsetInPush,
                          MachineInstr::FrameSetup);
-    MCSymbol *SPLabel = Context.CreateTempSymbol();
-    BuildMI(MBB, GPRCS1Push, dl, TII.get(TargetOpcode::PROLOG_LABEL))
-        .addSym(SPLabel);
     if (FramePtrOffsetInPush) {
       CFAOffset += FramePtrOffsetInPush;
-      MMI.addFrameInst(
-          MCCFIInstruction::createDefCfa(SPLabel,
-              MRI->getDwarfRegNum(FramePtr, true), CFAOffset));
-    } else
-      MMI.addFrameInst(
-          MCCFIInstruction::createDefCfaRegister(SPLabel,
-              MRI->getDwarfRegNum(FramePtr, true)));
+      unsigned CFIIndex = MMI.addFrameInst(MCCFIInstruction::createDefCfa(
+          nullptr, MRI->getDwarfRegNum(FramePtr, true), CFAOffset));
+      BuildMI(MBB, GPRCS1Push, dl, TII.get(TargetOpcode::CFI_INSTRUCTION))
+          .addCFIIndex(CFIIndex);
+
+    } else {
+      unsigned CFIIndex =
+          MMI.addFrameInst(MCCFIInstruction::createDefCfaRegister(
+              nullptr, MRI->getDwarfRegNum(FramePtr, true)));
+      BuildMI(MBB, GPRCS1Push, dl, TII.get(TargetOpcode::CFI_INSTRUCTION))
+          .addCFIIndex(CFIIndex);
+    }
   }
 
   if (GPRCS2Size > 0) {
-    MCSymbol *SPLabel = Context.CreateTempSymbol();
-    BuildMI(MBB, ++GPRCS2Push, dl, TII.get(TargetOpcode::PROLOG_LABEL))
-        .addSym(SPLabel);
+    MachineBasicBlock::iterator Pos = ++GPRCS2Push;
     if (!HasFP) {
       CFAOffset -= GPRCS2Size;
-      MMI.addFrameInst(
-          MCCFIInstruction::createDefCfaOffset(SPLabel, CFAOffset));
+      unsigned CFIIndex = MMI.addFrameInst(
+          MCCFIInstruction::createDefCfaOffset(nullptr, CFAOffset));
+      BuildMI(MBB, Pos, dl, TII.get(TargetOpcode::CFI_INSTRUCTION))
+          .addCFIIndex(CFIIndex);
     }
     for (std::vector<CalleeSavedInfo>::const_iterator I = CSI.begin(),
            E = CSI.end(); I != E; ++I) {
@@ -393,8 +394,10 @@ void ARMFrameLowering::emitPrologue(MachineFunction &MF) const {
         if (STI.isTargetMachO()) {
           unsigned DwarfReg =  MRI->getDwarfRegNum(Reg, true);
           unsigned Offset = MFI->getObjectOffset(FI);
-          MMI.addFrameInst(
-              MCCFIInstruction::createOffset(SPLabel, DwarfReg, Offset));
+          unsigned CFIIndex = MMI.addFrameInst(
+              MCCFIInstruction::createOffset(nullptr, DwarfReg, Offset));
+          BuildMI(MBB, Pos, dl, TII.get(TargetOpcode::CFI_INSTRUCTION))
+              .addCFIIndex(CFIIndex);
         }
         break;
       }
@@ -404,24 +407,17 @@ void ARMFrameLowering::emitPrologue(MachineFunction &MF) const {
   if (DPRCSSize > 0) {
     // Since vpush register list cannot have gaps, there may be multiple vpush
     // instructions in the prologue.
-    MCSymbol *SPLabel = NULL;
     do {
       MachineBasicBlock::iterator Push = DPRCSPush++;
       if (!HasFP) {
-        SPLabel = Context.CreateTempSymbol();
-        BuildMI(MBB, DPRCSPush, dl, TII.get(TargetOpcode::PROLOG_LABEL))
-            .addSym(SPLabel);
         CFAOffset -= sizeOfSPAdjustment(Push);;
-        MMI.addFrameInst(
-            MCCFIInstruction::createDefCfaOffset(SPLabel, CFAOffset));
+        unsigned CFIIndex = MMI.addFrameInst(
+            MCCFIInstruction::createDefCfaOffset(nullptr, CFAOffset));
+        BuildMI(MBB, DPRCSPush, dl, TII.get(TargetOpcode::CFI_INSTRUCTION))
+            .addCFIIndex(CFIIndex);
       }
     } while (DPRCSPush->getOpcode() == ARM::VSTMDDB_UPD);
 
-    if (!SPLabel) {
-      SPLabel = Context.CreateTempSymbol();
-      BuildMI(MBB, DPRCSPush, dl, TII.get(TargetOpcode::PROLOG_LABEL))
-          .addSym(SPLabel);
-    }
     for (std::vector<CalleeSavedInfo>::const_iterator I = CSI.begin(),
            E = CSI.end(); I != E; ++I) {
       unsigned Reg = I->getReg();
@@ -430,20 +426,21 @@ void ARMFrameLowering::emitPrologue(MachineFunction &MF) const {
           (Reg < ARM::D8 || Reg >= ARM::D8 + AFI->getNumAlignedDPRCS2Regs())) {
         unsigned DwarfReg = MRI->getDwarfRegNum(Reg, true);
         unsigned Offset = MFI->getObjectOffset(FI);
-        MMI.addFrameInst(MCCFIInstruction::createOffset(SPLabel, DwarfReg,
-                                                        Offset));
+        unsigned CFIIndex = MMI.addFrameInst(
+            MCCFIInstruction::createOffset(nullptr, DwarfReg, Offset));
+        BuildMI(MBB, DPRCSPush, dl, TII.get(TargetOpcode::CFI_INSTRUCTION))
+            .addCFIIndex(CFIIndex);
       }
     }
   }
 
   if (NumBytes) {
     if (!HasFP) {
-      MCSymbol *SPLabel = Context.CreateTempSymbol();
-      BuildMI(MBB, MBBI, dl, TII.get(TargetOpcode::PROLOG_LABEL))
-          .addSym(SPLabel);
       CFAOffset -= NumBytes;
-      MMI.addFrameInst(
-          MCCFIInstruction::createDefCfaOffset(SPLabel, CFAOffset));
+      unsigned CFIIndex = MMI.addFrameInst(
+          MCCFIInstruction::createDefCfaOffset(nullptr, CFAOffset));
+      BuildMI(MBB, MBBI, dl, TII.get(TargetOpcode::CFI_INSTRUCTION))
+          .addCFIIndex(CFIIndex);
     }
   }