[Statepoints 2/4] Statepoint infrastructure for garbage collection: MI & x86-64 Backend
This is the second patch in a small series. This patch contains the MachineInstruction and x86-64 backend pieces required to lower Statepoints. It does not include the code to actually generate the STATEPOINT machine instruction and as a result, the entire patch is currently dead code. I will be submitting the SelectionDAG parts within the next 24-48 hours. Since those pieces are by far the most complicated, I wanted to minimize the size of that patch. That patch will include the tests which exercise the functionality in this patch. The entire series can be seen as one combined whole in http://reviews.llvm.org/D5683.
The STATEPOINT psuedo node is generated after all gc values are explicitly spilled to stack slots. The purpose of this node is to wrap an actual call instruction while recording the spill locations of the meta arguments used for garbage collection and other purposes. The STATEPOINT is modeled as modifing all of those locations to prevent backend optimizations from forwarding the value from before the STATEPOINT to after the STATEPOINT. (Doing so would break relocation semantics for collectors which wish to relocate roots.)
The implementation of STATEPOINT is closely modeled on PATCHPOINT. Eventually, much of the code in this patch will be removed. The long term plan is to merge the functionality provided by statepoints and patchpoints. Merging their implementations in the backend is likely to be a good starting point.
Reviewed by: atrick, ributzka
llvm-svn: 223085
diff --git a/llvm/lib/Target/X86/X86MCInstLower.cpp b/llvm/lib/Target/X86/X86MCInstLower.cpp
index 4e0d594..6a10916 100644
--- a/llvm/lib/Target/X86/X86MCInstLower.cpp
+++ b/llvm/lib/Target/X86/X86MCInstLower.cpp
@@ -808,6 +808,66 @@
} // while (NumBytes)
}
+static void LowerSTATEPOINT(MCStreamer &OS, StackMaps &SM,
+ const MachineInstr &MI, bool Is64Bit,
+ const TargetMachine& TM,
+ const MCSubtargetInfo& STI,
+ X86MCInstLower &MCInstLowering) {
+ assert(Is64Bit && "Statepoint currently only supports X86-64");
+
+ // We need to record the frame size for stack walking
+ const MachineFunction* MF = MI.getParent()->getParent();
+ assert(MF && "can't find machine function?");
+
+ //
+ // Emit call instruction
+ //
+
+ // Lower call target and choose correct opcode
+ const MachineOperand &call_target = StatepointOpers(&MI).getCallTarget();
+ MCOperand call_target_mcop;
+ unsigned call_opcode;
+ switch (call_target.getType()) {
+ case MachineOperand::MO_GlobalAddress:
+ case MachineOperand::MO_ExternalSymbol:
+ call_target_mcop = MCInstLowering.LowerSymbolOperand(
+ call_target,
+ MCInstLowering.GetSymbolFromOperand(call_target));
+ call_opcode = X86::CALL64pcrel32;
+ // Currently, we only support relative addressing with statepoints.
+ // Otherwise, we'll need a scratch register to hold the target
+ // address. You'll fail asserts during load & relocation if this
+ // symbol is to far away. (TODO: support non-relative addressing)
+ break;
+ case MachineOperand::MO_Immediate:
+ call_target_mcop = MCOperand::CreateImm(call_target.getImm());
+ call_opcode = X86::CALL64pcrel32;
+ // Currently, we only support relative addressing with statepoints.
+ // Otherwise, we'll need a scratch register to hold the target
+ // immediate. You'll fail asserts during load & relocation if this
+ // address is to far away. (TODO: support non-relative addressing)
+ break;
+ case MachineOperand::MO_Register:
+ call_target_mcop = MCOperand::CreateReg(call_target.getReg());
+ call_opcode = X86::CALL64r;
+ break;
+ default:
+ llvm_unreachable("Unsupported operand type in statepoint call target");
+ break;
+ }
+
+ // Emit call
+ MCInst call_inst;
+ call_inst.setOpcode(call_opcode);
+ call_inst.addOperand(call_target_mcop);
+ OS.EmitInstruction(call_inst, STI);
+
+ // Record our statepoint node in the same section used by STACKMAP
+ // and PATCHPOINT
+ SM.recordStatepoint(MI);
+}
+
+
// Lower a stackmap of the form:
// <id>, <shadowBytes>, ...
void X86AsmPrinter::LowerSTACKMAP(const MachineInstr &MI) {
@@ -1030,7 +1090,9 @@
.addExpr(DotExpr));
return;
}
-
+ case TargetOpcode::STATEPOINT:
+ return LowerSTATEPOINT(OutStreamer, SM, *MI, Subtarget->is64Bit(), TM,
+ getSubtargetInfo(), MCInstLowering);
case TargetOpcode::STACKMAP:
return LowerSTACKMAP(*MI);