[CodeGen] Introduce a FAULTING_LOAD_OP pseudo-op.
Summary:
This instruction encodes a loading operation that may fault, and a label
to branch to if the load page-faults. The locations of potentially
faulting loads and their "handler" destinations are recorded in a
FaultMap section, meant to be consumed by LLVM's clients.
Nothing generates FAULTING_LOAD_OP instructions yet, but they will be
used in a future change.
The documentation (FaultMaps.rst) needs improvement and I will update
this diff with a more expanded version shortly.
Depends on D10196
Reviewers: rnk, reames, AndyAyers, ab, atrick, pgavlin
Reviewed By: atrick, pgavlin
Subscribers: llvm-commits
Differential Revision: http://reviews.llvm.org/D10197
llvm-svn: 239740
diff --git a/llvm/lib/Target/X86/X86MCInstLower.cpp b/llvm/lib/Target/X86/X86MCInstLower.cpp
index e47ab17..655e06a 100644
--- a/llvm/lib/Target/X86/X86MCInstLower.cpp
+++ b/llvm/lib/Target/X86/X86MCInstLower.cpp
@@ -864,6 +864,28 @@
SM.recordStatepoint(MI);
}
+void X86AsmPrinter::LowerFAULTING_LOAD_OP(const MachineInstr &MI,
+ X86MCInstLower &MCIL) {
+ // FAULTING_LOAD_OP <def>, <handler label>, <load opcode>, <load operands>
+
+ unsigned LoadDefRegister = MI.getOperand(0).getReg();
+ MCSymbol *HandlerLabel = MI.getOperand(1).getMCSymbol();
+ unsigned LoadOpcode = MI.getOperand(2).getImm();
+ unsigned LoadOperandsBeginIdx = 3;
+
+ FM.recordFaultingOp(FaultMaps::FaultingLoad, HandlerLabel);
+
+ MCInst LoadMI;
+ LoadMI.setOpcode(LoadOpcode);
+ LoadMI.addOperand(MCOperand::createReg(LoadDefRegister));
+ for (auto I = MI.operands_begin() + LoadOperandsBeginIdx,
+ E = MI.operands_end();
+ I != E; ++I)
+ if (auto MaybeOperand = MCIL.LowerMachineOperand(&MI, *I))
+ LoadMI.addOperand(MaybeOperand.getValue());
+
+ OutStreamer->EmitInstruction(LoadMI, getSubtargetInfo());
+}
// Lower a stackmap of the form:
// <id>, <shadowBytes>, ...
@@ -1119,6 +1141,9 @@
case TargetOpcode::STATEPOINT:
return LowerSTATEPOINT(*MI, MCInstLowering);
+ case TargetOpcode::FAULTING_LOAD_OP:
+ return LowerFAULTING_LOAD_OP(*MI, MCInstLowering);
+
case TargetOpcode::STACKMAP:
return LowerSTACKMAP(*MI);