[llvm] r301211 - X86RegisterInfo: eliminateFrameIndex: Avoid code duplication; NFC

[Matthias Braun via llvm-commits]

Author: matze
Date: Mon Apr 24 13:15:00 2017
New Revision: 301211

URL: http://llvm.org/viewvc/llvm-project?rev=301211&view=rev
Log:
X86RegisterInfo: eliminateFrameIndex: Avoid code duplication; NFC

Re-Commit of r300922 and r300923 with less aggressive assert (see
discussion at the end of https://reviews.llvm.org/D32205)

X86RegisterInfo::eliminateFrameIndex() and
X86FrameLowering::getFrameIndexReference() both had logic to compute the
base register. This consolidates the code.

Also use MachineInstr::isReturn instead of manually enumerating tail
call instructions (return instructions were not included in the previous
list because they never reference frame indexes).

Differential Revision: https://reviews.llvm.org/D32206

Modified:
    llvm/trunk/lib/Target/X86/X86FrameLowering.cpp
    llvm/trunk/lib/Target/X86/X86FrameLowering.h
    llvm/trunk/lib/Target/X86/X86RegisterInfo.cpp

Modified: llvm/trunk/lib/Target/X86/X86FrameLowering.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/X86FrameLowering.cpp?rev=301211&r1=301210&r2=301211&view=diff
==============================================================================
--- llvm/trunk/lib/Target/X86/X86FrameLowering.cpp (original)
+++ llvm/trunk/lib/Target/X86/X86FrameLowering.cpp Mon Apr 24 13:15:00 2017
@@ -1783,6 +1783,14 @@ int X86FrameLowering::getFrameIndexRefer
   return Offset + FPDelta;
 }
 
+int X86FrameLowering::getFrameIndexReferenceSP(const MachineFunction &MF,
+                                               int FI, unsigned &FrameReg,
+                                               int Adjustment) const {
+  const MachineFrameInfo &MFI = MF.getFrameInfo();
+  FrameReg = TRI->getStackRegister();
+  return MFI.getObjectOffset(FI) - getOffsetOfLocalArea() + Adjustment;
+}
+
 int
 X86FrameLowering::getFrameIndexReferencePreferSP(const MachineFunction &MF,
                                                  int FI, unsigned &FrameReg,
@@ -1839,9 +1847,6 @@ X86FrameLowering::getFrameIndexReference
   assert(MF.getInfo<X86MachineFunctionInfo>()->getTCReturnAddrDelta() >= 0 &&
          "we don't handle this case!");
 
-  // Fill in FrameReg output argument.
-  FrameReg = TRI->getStackRegister();
-
   // This is how the math works out:
   //
   //  %rsp grows (i.e. gets lower) left to right. Each box below is
@@ -1866,12 +1871,8 @@ X86FrameLowering::getFrameIndexReference
   // (C - E) == (C - A) - (B - A) + (B - E)
   //            { Using [1], [2] and [3] above }
   //         == getObjectOffset - LocalAreaOffset + StackSize
-  //
-
-  // Get the Offset from the StackPointer
-  int Offset = MFI.getObjectOffset(FI) - getOffsetOfLocalArea();
 
-  return Offset + StackSize;
+  return getFrameIndexReferenceSP(MF, FI, FrameReg, StackSize);
 }
 
 bool X86FrameLowering::assignCalleeSavedSpillSlots(

Modified: llvm/trunk/lib/Target/X86/X86FrameLowering.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/X86FrameLowering.h?rev=301211&r1=301210&r2=301211&view=diff
==============================================================================
--- llvm/trunk/lib/Target/X86/X86FrameLowering.h (original)
+++ llvm/trunk/lib/Target/X86/X86FrameLowering.h Mon Apr 24 13:15:00 2017
@@ -100,6 +100,8 @@ public:
   int getFrameIndexReference(const MachineFunction &MF, int FI,
                              unsigned &FrameReg) const override;
 
+  int getFrameIndexReferenceSP(const MachineFunction &MF,
+                               int FI, unsigned &SPReg, int Adjustment) const;
   int getFrameIndexReferencePreferSP(const MachineFunction &MF, int FI,
                                      unsigned &FrameReg,
                                      bool IgnoreSPUpdates) const override;

Modified: llvm/trunk/lib/Target/X86/X86RegisterInfo.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/X86RegisterInfo.cpp?rev=301211&r1=301210&r2=301211&view=diff
==============================================================================
--- llvm/trunk/lib/Target/X86/X86RegisterInfo.cpp (original)
+++ llvm/trunk/lib/Target/X86/X86RegisterInfo.cpp Mon Apr 24 13:15:00 2017
@@ -669,32 +669,28 @@ X86RegisterInfo::eliminateFrameIndex(Mac
   MachineFunction &MF = *MI.getParent()->getParent();
   const X86FrameLowering *TFI = getFrameLowering(MF);
   int FrameIndex = MI.getOperand(FIOperandNum).getIndex();
-  unsigned BasePtr;
-
-  unsigned Opc = MI.getOpcode();
-  bool AfterFPPop = Opc == X86::TAILJMPm64 || Opc == X86::TAILJMPm ||
-                    Opc == X86::TCRETURNmi || Opc == X86::TCRETURNmi64;
 
-  if (hasBasePointer(MF))
-    BasePtr = (FrameIndex < 0 ? FramePtr : getBaseRegister());
-  else if (needsStackRealignment(MF))
-    BasePtr = (FrameIndex < 0 ? FramePtr : StackPtr);
-  else if (AfterFPPop)
-    BasePtr = StackPtr;
-  else
-    BasePtr = (TFI->hasFP(MF) ? FramePtr : StackPtr);
+  // Determine base register and offset.
+  int FIOffset;
+  unsigned BasePtr;
+  if (MI.isReturn()) {
+    assert((!needsStackRealignment(MF) ||
+           MF.getFrameInfo().isFixedObjectIndex(FrameIndex)) &&
+           "Return instruction can only reference SP relative frame objects");
+    FIOffset = TFI->getFrameIndexReferenceSP(MF, FrameIndex, BasePtr, 0);
+  } else {
+    FIOffset = TFI->getFrameIndexReference(MF, FrameIndex, BasePtr);
+  }
 
   // LOCAL_ESCAPE uses a single offset, with no register. It only works in the
   // simple FP case, and doesn't work with stack realignment. On 32-bit, the
   // offset is from the traditional base pointer location.  On 64-bit, the
   // offset is from the SP at the end of the prologue, not the FP location. This
   // matches the behavior of llvm.frameaddress.
-  unsigned IgnoredFrameReg;
+  unsigned Opc = MI.getOpcode();
   if (Opc == TargetOpcode::LOCAL_ESCAPE) {
     MachineOperand &FI = MI.getOperand(FIOperandNum);
-    int Offset;
-    Offset = TFI->getFrameIndexReference(MF, FrameIndex, IgnoredFrameReg);
-    FI.ChangeToImmediate(Offset);
+    FI.ChangeToImmediate(FIOffset);
     return;
   }
 
@@ -710,15 +706,6 @@ X86RegisterInfo::eliminateFrameIndex(Mac
   // FrameIndex with base register.  Add an offset to the offset.
   MI.getOperand(FIOperandNum).ChangeToRegister(MachineBasePtr, false);
 
-  // Now add the frame object offset to the offset from EBP.
-  int FIOffset;
-  if (AfterFPPop) {
-    // Tail call jmp happens after FP is popped.
-    const MachineFrameInfo &MFI = MF.getFrameInfo();
-    FIOffset = MFI.getObjectOffset(FrameIndex) - TFI->getOffsetOfLocalArea();
-  } else
-    FIOffset = TFI->getFrameIndexReference(MF, FrameIndex, IgnoredFrameReg);
-
   if (BasePtr == StackPtr)
     FIOffset += SPAdj;