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.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@203204 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 16 insertions, 25 deletions

diff --git a/lib/Target/AArch64/AArch64FrameLowering.cpp b/lib/Target/AArch64/AArch64FrameLowering.cpp
index 410295e339..b29587a413 100644
--- a/lib/Target/AArch64/AArch64FrameLowering.cpp
+++ b/lib/Target/AArch64/AArch64FrameLowering.cpp
@@ -92,14 +92,12 @@ void AArch64FrameLowering::emitPrologue(MachineFunction &MF) const {
   if (NeedsFrameMoves && NumInitialBytes) {
     // We emit this update even if the CFA is set from a frame pointer later so
     // that the CFA is valid in the interim.
-    MCSymbol *SPLabel = MMI.getContext().CreateTempSymbol();
-    BuildMI(MBB, MBBI, DL, TII.get(TargetOpcode::PROLOG_LABEL))
-      .addSym(SPLabel);
-
     MachineLocation Dst(MachineLocation::VirtualFP);
     unsigned Reg = MRI->getDwarfRegNum(AArch64::XSP, true);
-    MMI.addFrameInst(
-        MCCFIInstruction::createDefCfa(SPLabel, Reg, -NumInitialBytes));
+    unsigned CFIIndex = MMI.addFrameInst(
+        MCCFIInstruction::createDefCfa(nullptr, Reg, -NumInitialBytes));
+    BuildMI(MBB, MBBI, DL, TII.get(TargetOpcode::CFI_INSTRUCTION))
+        .addCFIIndex(CFIIndex);
   }
 
   // Otherwise we need to set the frame pointer and/or add a second stack
@@ -129,12 +127,12 @@ void AArch64FrameLowering::emitPrologue(MachineFunction &MF) const {
                                - MFI->getStackSize());
 
       if (NeedsFrameMoves) {
-        MCSymbol *FPLabel = MMI.getContext().CreateTempSymbol();
-        BuildMI(MBB, MBBI, DL, TII.get(TargetOpcode::PROLOG_LABEL))
-          .addSym(FPLabel);
         unsigned Reg = MRI->getDwarfRegNum(AArch64::X29, true);
         unsigned Offset = MFI->getObjectOffset(X29FrameIdx);
-        MMI.addFrameInst(MCCFIInstruction::createDefCfa(FPLabel, Reg, Offset));
+        unsigned CFIIndex = MMI.addFrameInst(
+            MCCFIInstruction::createDefCfa(nullptr, Reg, Offset));
+        BuildMI(MBB, MBBI, DL, TII.get(TargetOpcode::CFI_INSTRUCTION))
+            .addCFIIndex(CFIIndex);
       }
 
       FPNeedsSetting = false;
@@ -155,36 +153,29 @@ void AArch64FrameLowering::emitPrologue(MachineFunction &MF) const {
   if (!NeedsFrameMoves)
     return;
 
-  // Reuse the label if appropriate, so create it in this outer scope.
-  MCSymbol *CSLabel = 0;
-
   // The rest of the stack adjustment
   if (!hasFP(MF) && NumResidualBytes) {
-    CSLabel = MMI.getContext().CreateTempSymbol();
-    BuildMI(MBB, MBBI, DL, TII.get(TargetOpcode::PROLOG_LABEL))
-      .addSym(CSLabel);
-
     MachineLocation Dst(MachineLocation::VirtualFP);
     unsigned Reg = MRI->getDwarfRegNum(AArch64::XSP, true);
     unsigned Offset = NumResidualBytes + NumInitialBytes;
-    MMI.addFrameInst(MCCFIInstruction::createDefCfa(CSLabel, Reg, -Offset));
+    unsigned CFIIndex =
+        MMI.addFrameInst(MCCFIInstruction::createDefCfa(nullptr, Reg, -Offset));
+    BuildMI(MBB, MBBI, DL, TII.get(TargetOpcode::CFI_INSTRUCTION))
+        .addCFIIndex(CFIIndex);
   }
 
   // And any callee-saved registers (it's fine to leave them to the end here,
   // because the old values are still valid at this point.
   const std::vector<CalleeSavedInfo> &CSI = MFI->getCalleeSavedInfo();
   if (CSI.size()) {
-    if (!CSLabel) {
-      CSLabel = MMI.getContext().CreateTempSymbol();
-      BuildMI(MBB, MBBI, DL, TII.get(TargetOpcode::PROLOG_LABEL))
-        .addSym(CSLabel);
-    }
-
     for (std::vector<CalleeSavedInfo>::const_iterator I = CSI.begin(),
            E = CSI.end(); I != E; ++I) {
       unsigned Offset = MFI->getObjectOffset(I->getFrameIdx());
       unsigned Reg = MRI->getDwarfRegNum(I->getReg(), true);
-      MMI.addFrameInst(MCCFIInstruction::createOffset(CSLabel, Reg, Offset));
+      unsigned CFIIndex = MMI.addFrameInst(
+          MCCFIInstruction::createOffset(nullptr, Reg, Offset));
+      BuildMI(MBB, MBBI, DL, TII.get(TargetOpcode::CFI_INSTRUCTION))
+          .addCFIIndex(CFIIndex);
     }
   }
 }