Created
July 31, 2014 20:01
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Fix armv4t return
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diff --git a/llvm/lib/Target/ARM/Thumb1FrameLowering.cpp b/llvm/lib/Target/ARM/Thumb1FrameLowering.cpp | |
index baa97a7..a30dfdd 100644 | |
--- a/llvm/lib/Target/ARM/Thumb1FrameLowering.cpp | |
+++ b/llvm/lib/Target/ARM/Thumb1FrameLowering.cpp | |
@@ -463,6 +463,7 @@ restoreCalleeSavedRegisters(MachineBasicBlock &MBB, | |
MachineInstrBuilder MIB = BuildMI(MF, DL, TII.get(ARM::tPOP)); | |
AddDefaultPred(MIB); | |
+ bool IsReturn = false; | |
bool NumRegs = false; | |
for (unsigned i = CSI.size(); i != 0; --i) { | |
unsigned Reg = CSI[i-1].getReg(); | |
@@ -470,6 +471,9 @@ restoreCalleeSavedRegisters(MachineBasicBlock &MBB, | |
// Special epilogue for vararg functions. See emitEpilogue | |
if (isVarArg) | |
continue; | |
+ IsReturn = true; | |
+ if (STI.hasV4TOps() && !STI.hasV5TOps()) | |
+ continue; | |
Reg = ARM::PC; | |
(*MIB).setDesc(TII.get(ARM::tPOP_RET)); | |
MIB.copyImplicitOps(&*MI); | |
@@ -485,5 +489,27 @@ restoreCalleeSavedRegisters(MachineBasicBlock &MBB, | |
else | |
MF.DeleteMachineInstr(MIB); | |
+ // On armv4, popping into PC will not change arm/thumb state, | |
+ // so instead we have to emit that as: | |
+ // POP {r3} | |
+ // BX r3 | |
+ if (IsReturn && STI.hasV4TOps() && !STI.hasV5TOps()) { | |
+ // Get the last instruction, tBX_RET | |
+ MI = MBB.getLastNonDebugInstr(); | |
+ assert (MI->getOpcode() == ARM::tBX_RET); | |
+ DebugLoc dl = MI->getDebugLoc(); | |
+ // Epilogue: pop LR to R3 and branch off it. | |
+ AddDefaultPred(BuildMI(MBB, MI, dl, TII.get(ARM::tPOP))) | |
+ .addReg(ARM::R3, RegState::Define); | |
+ | |
+ MachineInstrBuilder MIB = | |
+ BuildMI(MBB, MI, dl, TII.get(ARM::tBX)) | |
+ .addReg(ARM::R3, RegState::Kill); | |
+ AddDefaultPred(MIB); | |
+ MIB.copyImplicitOps(&*MI); | |
+ // erase the old tBX_RET instruction | |
+ MBB.erase(MI); | |
+ } | |
+ | |
return true; | |
} |
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