diff options
Diffstat (limited to 'lib/Target/X86/X86MCInstLower.cpp')
| -rw-r--r-- | lib/Target/X86/X86MCInstLower.cpp | 80 |
1 files changed, 80 insertions, 0 deletions
diff --git a/lib/Target/X86/X86MCInstLower.cpp b/lib/Target/X86/X86MCInstLower.cpp index 550e3543a71e8..598d88d8b9c3b 100644 --- a/lib/Target/X86/X86MCInstLower.cpp +++ b/lib/Target/X86/X86MCInstLower.cpp @@ -1040,6 +1040,83 @@ void X86AsmPrinter::LowerPATCHPOINT(const MachineInstr &MI, getSubtargetInfo()); } +void X86AsmPrinter::LowerPATCHABLE_EVENT_CALL(const MachineInstr &MI, + X86MCInstLower &MCIL) { + assert(Subtarget->is64Bit() && "XRay custom events only suports X86-64"); + + // We want to emit the following pattern, which follows the x86 calling + // convention to prepare for the trampoline call to be patched in. + // + // <args placement according SysV64 calling convention> + // .p2align 1, ... + // .Lxray_event_sled_N: + // jmp +N // jump across the call instruction + // callq __xray_CustomEvent // force relocation to symbol + // <args cleanup, jump to here> + // + // The relative jump needs to jump forward 24 bytes: + // 10 (args) + 5 (nops) + 9 (cleanup) + // + // After patching, it would look something like: + // + // nopw (2-byte nop) + // callq __xrayCustomEvent // already lowered + // + // --- + // First we emit the label and the jump. + auto CurSled = OutContext.createTempSymbol("xray_event_sled_", true); + OutStreamer->AddComment("# XRay Custom Event Log"); + OutStreamer->EmitCodeAlignment(2); + OutStreamer->EmitLabel(CurSled); + + // Use a two-byte `jmp`. This version of JMP takes an 8-bit relative offset as + // an operand (computed as an offset from the jmp instruction). + // FIXME: Find another less hacky way do force the relative jump. + OutStreamer->EmitBytes("\xeb\x14"); + + // The default C calling convention will place two arguments into %rcx and + // %rdx -- so we only work with those. + unsigned UsedRegs[] = {X86::RDI, X86::RSI, X86::RAX}; + + // Because we will use %rax, we preserve that across the call. + EmitAndCountInstruction(MCInstBuilder(X86::PUSH64r).addReg(X86::RAX)); + + // Then we put the operands in the %rdi and %rsi registers. + for (unsigned I = 0; I < MI.getNumOperands(); ++I) + if (auto Op = MCIL.LowerMachineOperand(&MI, MI.getOperand(I))) { + if (Op->isImm()) + EmitAndCountInstruction(MCInstBuilder(X86::MOV64ri) + .addReg(UsedRegs[I]) + .addImm(Op->getImm())); + else if (Op->isReg()) { + if (Op->getReg() != UsedRegs[I]) + EmitAndCountInstruction(MCInstBuilder(X86::MOV64rr) + .addReg(UsedRegs[I]) + .addReg(Op->getReg())); + else + EmitNops(*OutStreamer, 3, Subtarget->is64Bit(), getSubtargetInfo()); + } + } + + // We emit a hard dependency on the __xray_CustomEvent symbol, which is the + // name of the trampoline to be implemented by the XRay runtime. We put this + // explicitly in the %rax register. + auto TSym = OutContext.getOrCreateSymbol("__xray_CustomEvent"); + MachineOperand TOp = MachineOperand::CreateMCSymbol(TSym); + EmitAndCountInstruction(MCInstBuilder(X86::MOV64ri) + .addReg(X86::RAX) + .addOperand(MCIL.LowerSymbolOperand(TOp, TSym))); + + // Emit the call instruction. + EmitAndCountInstruction(MCInstBuilder(X86::CALL64r).addReg(X86::RAX)); + + // Restore caller-saved and used registers. + OutStreamer->AddComment("xray custom event end."); + EmitAndCountInstruction(MCInstBuilder(X86::POP64r).addReg(X86::RAX)); + + recordSled(CurSled, MI, SledKind::CUSTOM_EVENT); +} + void X86AsmPrinter::LowerPATCHABLE_FUNCTION_ENTER(const MachineInstr &MI, X86MCInstLower &MCIL) { // We want to emit the following pattern: @@ -1415,6 +1492,9 @@ void X86AsmPrinter::EmitInstruction(const MachineInstr *MI) { case TargetOpcode::PATCHABLE_TAIL_CALL: return LowerPATCHABLE_TAIL_CALL(*MI, MCInstLowering); + + case TargetOpcode::PATCHABLE_EVENT_CALL: + return LowerPATCHABLE_EVENT_CALL(*MI, MCInstLowering); case X86::MORESTACK_RET: EmitAndCountInstruction(MCInstBuilder(getRetOpcode(*Subtarget))); |