[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

5 files changed, 42 insertions, 2 deletions

diff --git a/llvm/lib/CodeGen/InlineSpiller.cpp b/llvm/lib/CodeGen/InlineSpiller.cpp
index 6a6e15dabff..121a89e0da2 100644
--- a/llvm/lib/CodeGen/InlineSpiller.cpp
+++ b/llvm/lib/CodeGen/InlineSpiller.cpp
@@ -1088,7 +1088,8 @@ foldMemoryOperand(ArrayRef<std::pair<MachineInstr*, unsigned> > Ops,
   bool WasCopy = MI->isCopy();
   unsigned ImpReg = 0;
 
-  bool SpillSubRegs = (MI->getOpcode() == TargetOpcode::PATCHPOINT ||
+  bool SpillSubRegs = (MI->getOpcode() == TargetOpcode::STATEPOINT ||
+                       MI->getOpcode() == TargetOpcode::PATCHPOINT ||
                        MI->getOpcode() == TargetOpcode::STACKMAP);
 
   // TargetInstrInfo::foldMemoryOperand only expects explicit, non-tied
diff --git a/llvm/lib/CodeGen/LocalStackSlotAllocation.cpp b/llvm/lib/CodeGen/LocalStackSlotAllocation.cpp
index 5c5712f37e1..e8bf687a626 100644
--- a/llvm/lib/CodeGen/LocalStackSlotAllocation.cpp
+++ b/llvm/lib/CodeGen/LocalStackSlotAllocation.cpp
@@ -291,6 +291,7 @@ bool LocalStackSlotPass::insertFrameReferenceRegisters(MachineFunction &Fn) {
       // Debug value, stackmap and patchpoint instructions can't be out of
       // range, so they don't need any updates.
       if (MI->isDebugValue() ||
+          MI->getOpcode() == TargetOpcode::STATEPOINT ||
           MI->getOpcode() == TargetOpcode::STACKMAP ||
           MI->getOpcode() == TargetOpcode::PATCHPOINT)
         continue;
diff --git a/llvm/lib/CodeGen/PrologEpilogInserter.cpp b/llvm/lib/CodeGen/PrologEpilogInserter.cpp
index 06530b91d67..a19bd96b3f5 100644
--- a/llvm/lib/CodeGen/PrologEpilogInserter.cpp
+++ b/llvm/lib/CodeGen/PrologEpilogInserter.cpp
@@ -797,6 +797,26 @@ void PEI::replaceFrameIndices(MachineBasicBlock *BB, MachineFunction &Fn,
         continue;
       }
 
+      // TODO: This code should be commoned with the code for
+      // PATCHPOINT. There's no good reason for the difference in
+      // implementation other than historical accident.  The only
+      // remaining difference is the unconditional use of the stack
+      // pointer as the base register.
+      if (MI->getOpcode() == TargetOpcode::STATEPOINT) {
+        assert((!MI->isDebugValue() || i == 0) &&
+               "Frame indicies can only appear as the first operand of a "
+               "DBG_VALUE machine instruction");
+        unsigned Reg;
+        MachineOperand &Offset = MI->getOperand(i + 1);
+        const unsigned refOffset =
+          TFI->getFrameIndexReferenceFromSP(Fn, MI->getOperand(i).getIndex(),
+                                            Reg);
+
+        Offset.setImm(Offset.getImm() + refOffset);
+        MI->getOperand(i).ChangeToRegister(Reg, false /*isDef*/);
+        continue;
+      }
+
       // Some instructions (e.g. inline asm instructions) can have
       // multiple frame indices and/or cause eliminateFrameIndex
       // to insert more than one instruction. We need the register
diff --git a/llvm/lib/CodeGen/StackMaps.cpp b/llvm/lib/CodeGen/StackMaps.cpp
index d3791c3feb5..aab8d522144 100644
--- a/llvm/lib/CodeGen/StackMaps.cpp
+++ b/llvm/lib/CodeGen/StackMaps.cpp
@@ -286,6 +286,18 @@ void StackMaps::recordPatchPoint(const MachineInstr &MI) {
   }
 #endif
 }
+void StackMaps::recordStatepoint(const MachineInstr &MI) {
+  assert(MI.getOpcode() == TargetOpcode::STATEPOINT &&
+         "expected statepoint");
+
+  StatepointOpers opers(&MI);
+  // Record all the deopt and gc operands (they're contiguous and run from the
+  // initial index to the end of the operand list)
+  const unsigned StartIdx = opers.getVarIdx();
+  recordStackMapOpers(MI, 0xABCDEF00,
+                      MI.operands_begin() + StartIdx, MI.operands_end(),
+                      false);
+}
 
 /// Emit the stackmap header.
 ///
diff --git a/llvm/lib/CodeGen/TargetLoweringBase.cpp b/llvm/lib/CodeGen/TargetLoweringBase.cpp
index bd5cd4c8cc2..8805104689e 100644
--- a/llvm/lib/CodeGen/TargetLoweringBase.cpp
+++ b/llvm/lib/CodeGen/TargetLoweringBase.cpp
@@ -992,8 +992,14 @@ TargetLoweringBase::emitPatchPoint(MachineInstr *MI,
     // Add a new memory operand for this FI.
     const MachineFrameInfo &MFI = *MF.getFrameInfo();
     assert(MFI.getObjectOffset(FI) != -1);
+
+    unsigned Flags = MachineMemOperand::MOLoad;
+    if (MI->getOpcode() == TargetOpcode::STATEPOINT) {
+      Flags |= MachineMemOperand::MOStore;
+      Flags |= MachineMemOperand::MOVolatile;
+    }
     MachineMemOperand *MMO = MF.getMachineMemOperand(
-        MachinePointerInfo::getFixedStack(FI), MachineMemOperand::MOLoad,
+        MachinePointerInfo::getFixedStack(FI), Flags,
         TM.getSubtargetImpl()->getDataLayout()->getPointerSize(),
         MFI.getObjectAlignment(FI));
     MIB->addMemOperand(MF, MMO);