diff options
Diffstat (limited to 'llvm/lib/Target/WebAssembly/WebAssemblyFrameLowering.cpp')
| -rw-r--r-- | llvm/lib/Target/WebAssembly/WebAssemblyFrameLowering.cpp | 98 |
1 files changed, 89 insertions, 9 deletions
diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyFrameLowering.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyFrameLowering.cpp index 2b70952e360..8b0f48f4bd1 100644 --- a/llvm/lib/Target/WebAssembly/WebAssemblyFrameLowering.cpp +++ b/llvm/lib/Target/WebAssembly/WebAssemblyFrameLowering.cpp @@ -35,6 +35,10 @@ using namespace llvm; #define DEBUG_TYPE "wasm-frame-info" // TODO: Implement a red zone? +// TODO: wasm64 +// TODO: Prolog/epilog should be stackified too. This pass runs after register +// stackification, so we'll have to do it manually. +// TODO: Emit TargetOpcode::CFI_INSTRUCTION instructions /// Return true if the specified function should have a dedicated frame pointer /// register. @@ -42,9 +46,9 @@ bool WebAssemblyFrameLowering::hasFP(const MachineFunction &MF) const { const MachineFrameInfo *MFI = MF.getFrameInfo(); const auto *RegInfo = MF.getSubtarget<WebAssemblySubtarget>().getRegisterInfo(); - return MFI->hasCalls() || MFI->hasVarSizedObjects() || - MFI->isFrameAddressTaken() || MFI->hasStackMap() || - MFI->hasPatchPoint() || RegInfo->needsStackRealignment(MF); + return MFI->hasVarSizedObjects() || MFI->isFrameAddressTaken() || + MFI->hasStackMap() || MFI->hasPatchPoint() || + RegInfo->needsStackRealignment(MF); } /// Under normal circumstances, when a frame pointer is not required, we reserve @@ -63,12 +67,88 @@ void WebAssemblyFrameLowering::eliminateCallFramePseudoInstr( llvm_unreachable("TODO: implement eliminateCallFramePseudoInstr"); } -void WebAssemblyFrameLowering::emitPrologue(MachineFunction & /*MF*/, - MachineBasicBlock & /*MBB*/) const { - llvm_unreachable("TODO: implement emitPrologue"); +void WebAssemblyFrameLowering::emitPrologue(MachineFunction &MF, + MachineBasicBlock &MBB) const { + // TODO: Do ".setMIFlag(MachineInstr::FrameSetup)" on emitted instructions + auto *MFI = MF.getFrameInfo(); + assert(MFI->getCalleeSavedInfo().empty() && + "WebAssembly should not have callee-saved registers"); + assert(!hasFP(MF) && "Functions needing frame pointers not yet supported"); + assert(!MFI->adjustsStack() && "Dynamic stack adjustmet not yet supported"); + uint64_t StackSize = MFI->getStackSize(); + if (!StackSize) + return; + + const auto *TII = MF.getSubtarget().getInstrInfo(); + auto &MRI = MF.getRegInfo(); + auto InsertPt = MBB.begin(); + DebugLoc DL; + + // Get the current stacktop + // TODO: To support dynamic alloc, also copy to FP + unsigned SPReg = MRI.createVirtualRegister(&WebAssembly::I32RegClass); + auto *SPSymbol = MF.createExternalSymbolName("__stack_pointer"); + BuildMI(MBB, InsertPt, DL, TII->get(WebAssembly::CONST_I32), SPReg) + .addExternalSymbol(SPSymbol); + // This MachinePointerInfo should reference __stack_pointer as well but + // doesn't because MachinePointerInfo() takes a GV which we don't have for + // __stack_pointer. TODO: check if PseudoSourceValue::ExternalSymbolCallEntry + // is appropriate instead. (likewise for EmitEpologue below) + auto *LoadMMO = new MachineMemOperand(MachinePointerInfo(), + MachineMemOperand::MOLoad, 4, 4); + BuildMI(MBB, InsertPt, DL, TII->get(WebAssembly::LOAD_I32), SPReg) + .addImm(0) + .addReg(SPReg) + .addMemOperand(LoadMMO); + // Subtract the frame size + unsigned OffsetReg = MRI.createVirtualRegister(&WebAssembly::I32RegClass); + BuildMI(MBB, InsertPt, DL, TII->get(WebAssembly::CONST_I32), OffsetReg) + .addImm(StackSize); + BuildMI(MBB, InsertPt, DL, TII->get(WebAssembly::SUB_I32), WebAssembly::SP32) + .addReg(SPReg) + .addReg(OffsetReg); + // The SP32 register now has the new stacktop. Also write it back to memory. + BuildMI(MBB, InsertPt, DL, TII->get(WebAssembly::CONST_I32), OffsetReg) + .addExternalSymbol(SPSymbol); + auto *MMO = new MachineMemOperand(MachinePointerInfo(), + MachineMemOperand::MOStore, 4, 4); + BuildMI(MBB, InsertPt, DL, TII->get(WebAssembly::STORE_I32), WebAssembly::SP32) + .addImm(0) + .addReg(OffsetReg) + .addReg(WebAssembly::SP32) + .addMemOperand(MMO); } -void WebAssemblyFrameLowering::emitEpilogue(MachineFunction & /*MF*/, - MachineBasicBlock & /*MBB*/) const { - llvm_unreachable("TODO: implement emitEpilogue"); +void WebAssemblyFrameLowering::emitEpilogue(MachineFunction &MF, + MachineBasicBlock &MBB) const { + uint64_t StackSize = MF.getFrameInfo()->getStackSize(); + if (!StackSize) + return; + const auto *TII = MF.getSubtarget().getInstrInfo(); + auto &MRI = MF.getRegInfo(); + unsigned OffsetReg = MRI.createVirtualRegister(&WebAssembly::I32RegClass); + auto InsertPt = MBB.getFirstTerminator(); + DebugLoc DL; + + if (InsertPt != MBB.end()) { + DL = InsertPt->getDebugLoc(); + } + + // Restore the stack pointer. Without FP its value is just SP32 - stacksize + BuildMI(MBB, InsertPt, DL, TII->get(WebAssembly::CONST_I32), OffsetReg) + .addImm(StackSize); + auto *SPSymbol = MF.createExternalSymbolName("__stack_pointer"); + BuildMI(MBB, InsertPt, DL, TII->get(WebAssembly::ADD_I32), WebAssembly::SP32) + .addReg(WebAssembly::SP32) + .addReg(OffsetReg); + // Re-use OffsetReg to hold the address of the stacktop + BuildMI(MBB, InsertPt, DL, TII->get(WebAssembly::CONST_I32), OffsetReg) + .addExternalSymbol(SPSymbol); + auto *MMO = new MachineMemOperand(MachinePointerInfo(), + MachineMemOperand::MOStore, 4, 4); + BuildMI(MBB, InsertPt, DL, TII->get(WebAssembly::STORE_I32), WebAssembly::SP32) + .addImm(0) + .addReg(OffsetReg) + .addReg(WebAssembly::SP32) + .addMemOperand(MMO); } |
