Reworking the stack layout that the MicroBlaze backend generates.

The MicroBlaze backend was generating stack layouts that did not
conform correctly to the ABI. This update generates stack layouts
which are closer to what GCC does.

Variable arguments support was added as well but the stack layout
for varargs has not been finalized.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@97807 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 50 insertions, 7 deletions

diff --git a/lib/Target/MBlaze/MBlazeRegisterInfo.cpp b/lib/Target/MBlaze/MBlazeRegisterInfo.cpp
index 9067f8b357..8dfca81fb2 100644
--- a/lib/Target/MBlaze/MBlazeRegisterInfo.cpp
+++ b/lib/Target/MBlaze/MBlazeRegisterInfo.cpp
@@ -85,6 +85,47 @@ unsigned MBlazeRegisterInfo::getRegisterNumbering(unsigned RegEnum) {
   return 0; // Not reached
 }
 
+/// getRegisterFromNumbering - Given the enum value for some register, e.g.
+/// MBlaze::R0, return the number that it corresponds to (e.g. 0).
+unsigned MBlazeRegisterInfo::getRegisterFromNumbering(unsigned Reg) {
+  switch (Reg) {
+    case 0  : return MBlaze::R0;
+    case 1  : return MBlaze::R1;
+    case 2  : return MBlaze::R2;
+    case 3  : return MBlaze::R3;
+    case 4  : return MBlaze::R4;
+    case 5  : return MBlaze::R5;
+    case 6  : return MBlaze::R6;
+    case 7  : return MBlaze::R7;
+    case 8  : return MBlaze::R8;
+    case 9  : return MBlaze::R9;
+    case 10 : return MBlaze::R10;
+    case 11 : return MBlaze::R11;
+    case 12 : return MBlaze::R12;
+    case 13 : return MBlaze::R13;
+    case 14 : return MBlaze::R14;
+    case 15 : return MBlaze::R15;
+    case 16 : return MBlaze::R16;
+    case 17 : return MBlaze::R17;
+    case 18 : return MBlaze::R18;
+    case 19 : return MBlaze::R19;
+    case 20 : return MBlaze::R20;
+    case 21 : return MBlaze::R21;
+    case 22 : return MBlaze::R22;
+    case 23 : return MBlaze::R23;
+    case 24 : return MBlaze::R24;
+    case 25 : return MBlaze::R25;
+    case 26 : return MBlaze::R26;
+    case 27 : return MBlaze::R27;
+    case 28 : return MBlaze::R28;
+    case 29 : return MBlaze::R29;
+    case 30 : return MBlaze::R30;
+    case 31 : return MBlaze::R31;
+    default: llvm_unreachable("Unknown register number!");
+  }
+  return 0; // Not reached
+}
+
 unsigned MBlazeRegisterInfo::getPICCallReg() {
   return MBlaze::R20;
 }
@@ -180,9 +221,9 @@ void MBlazeRegisterInfo::adjustMBlazeStackFrame(MachineFunction &MF) const {
   }
 
   if (MFI->hasCalls()) {
+    MBlazeFI->setRAStackOffset(0);
     MFI->setObjectOffset(MFI->CreateStackObject(RegSize, RegSize, true),
                          StackOffset);
-    MBlazeFI->setRAStackOffset(StackOffset);
     TopCPUSavedRegOff = StackOffset;
     StackOffset += RegSize;
   }
@@ -245,7 +286,7 @@ eliminateFrameIndex(MachineBasicBlock::iterator II, int SPAdj,
 
   // as explained on LowerFormalArguments, detect negative offsets
   // and adjust SPOffsets considering the final stack size.
-  int Offset = ((spOffset < 0) ? (stackSize + (-(spOffset+4))) : (spOffset));
+  int Offset = (spOffset < 0) ? (stackSize - spOffset) : (spOffset + 4);
   Offset    += MI.getOperand(oi).getImm();
 
   DEBUG(errs() << "Offset     : " << Offset << "\n" << "<--------->\n");
@@ -272,6 +313,7 @@ emitPrologue(MachineFunction &MF) const {
 
   // No need to allocate space on the stack.
   if (StackSize == 0 && !MFI->hasCalls()) return;
+  if (StackSize < 28 && MFI->hasCalls()) StackSize = 28;
 
   int FPOffset = MBlazeFI->getFPStackOffset();
   int RAOffset = MBlazeFI->getRAStackOffset();
@@ -307,9 +349,6 @@ emitEpilogue(MachineFunction &MF, MachineBasicBlock &MBB) const {
   MBlazeFunctionInfo *MBlazeFI         = MF.getInfo<MBlazeFunctionInfo>();
   DebugLoc dl = MBBI->getDebugLoc();
 
-  // Get the number of bytes from FrameInfo
-  int NumBytes = (int) MFI->getStackSize();
-
   // Get the FI's where RA and FP are saved.
   int FPOffset = MBlazeFI->getFPStackOffset();
   int RAOffset = MBlazeFI->getRAStackOffset();
@@ -333,11 +372,15 @@ emitEpilogue(MachineFunction &MF, MachineBasicBlock &MBB) const {
       .addImm(RAOffset).addReg(MBlaze::R1);
   }
 
+  // Get the number of bytes from FrameInfo
+  int StackSize = (int) MFI->getStackSize();
+  if (StackSize < 28 && MFI->hasCalls()) StackSize = 28;
+
   // adjust stack.
   // addi R1, R1, imm
-  if (NumBytes) {
+  if (StackSize) {
     BuildMI(MBB, MBBI, dl, TII.get(MBlaze::ADDI), MBlaze::R1)
-      .addReg(MBlaze::R1).addImm(NumBytes);
+      .addReg(MBlaze::R1).addImm(StackSize);
   }
 }