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[Statepoints] Use Indirect operands for spill slots
Teach the statepoint lowering code to emit Indirect stackmap entries for spill inserted by StatepointLowering (i.e. SelectionDAG), but Direct stackmap entries for in-IR allocas which represent manual stack slots. This is what the docs call for (http://llvm.org/docs/StackMaps.html#stack-map-format), but we've been emitting both as Direct. This was pointed out recently on the mailing list as a bug. It also blocks http://reviews.llvm.org/D15632 which extends the lowering to handle vector-of-pointers since only Indirect references can encode a variable sized slot. To implement this, I introduced a new flag on the StackObject class used to maintian information about stack slots. I original considered (and prototyped in http://reviews.llvm.org/D15632), the idea of using the existing isSpillSlot flag, but end up deciding that was a bit too risky and that the cost of adding a new flag was low. Having the new flag will also allow us - in the future - to emit better comments in verbose assembly which indicate where a particular stack spill around a call comes from. (deopt, gc, regalloc). Differential Revision: http://reviews.llvm.org/D15759 llvm-svn: 256352
This commit is contained in:
Philip Reames
parent
3787e623ca
commit
0d007cd82b
@ -101,6 +101,13 @@ class MachineFrameInfo {
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// cannot alias any other memory objects.
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bool isSpillSlot;
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/// If true, this stack slot is used to spill a value (could be deopt
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/// and/or GC related) over a statepoint. We know that the address of the
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/// slot can't alias any LLVM IR value. This is very similiar to a Spill
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/// Slot, but is created by statepoint lowering is SelectionDAG, not the
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/// register allocator.
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bool isStatepointSpillSlot;
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/// If this stack object is originated from an Alloca instruction
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/// this value saves the original IR allocation. Can be NULL.
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const AllocaInst *Alloca;
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@ -118,7 +125,8 @@ class MachineFrameInfo {
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StackObject(uint64_t Sz, unsigned Al, int64_t SP, bool IM,
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bool isSS, const AllocaInst *Val, bool A)
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: SPOffset(SP), Size(Sz), Alignment(Al), isImmutable(IM),
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isSpillSlot(isSS), Alloca(Val), PreAllocated(false), isAliased(A) {}
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isSpillSlot(isSS), isStatepointSpillSlot(false), Alloca(Val),
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PreAllocated(false), isAliased(A) {}
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};
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/// The alignment of the stack.
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@ -547,6 +555,12 @@ public:
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return Objects[ObjectIdx+NumFixedObjects].isSpillSlot;
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}
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bool isStatepointSpillSlotObjectIndex(int ObjectIdx) const {
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assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
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"Invalid Object Idx!");
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return Objects[ObjectIdx+NumFixedObjects].isStatepointSpillSlot;
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}
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/// Returns true if the specified index corresponds to a dead object.
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bool isDeadObjectIndex(int ObjectIdx) const {
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assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
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@ -562,6 +576,13 @@ public:
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return Objects[ObjectIdx + NumFixedObjects].Size == 0;
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}
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void markAsStatepointSpillSlotObjectIndex(int ObjectIdx) {
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assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
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"Invalid Object Idx!");
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Objects[ObjectIdx+NumFixedObjects].isStatepointSpillSlot = true;
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assert(isStatepointSpillSlotObjectIndex(ObjectIdx) && "inconsistent");
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}
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/// Create a new statically sized stack object, returning
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/// a nonnegative identifier to represent it.
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int CreateStackObject(uint64_t Size, unsigned Alignment, bool isSS,
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@ -17,6 +17,7 @@
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#include "llvm/ADT/SmallSet.h"
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#include "llvm/ADT/Statistic.h"
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#include "llvm/CodeGen/FunctionLoweringInfo.h"
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#include "llvm/CodeGen/MachineFrameInfo.h"
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#include "llvm/CodeGen/GCMetadata.h"
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#include "llvm/CodeGen/GCStrategy.h"
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#include "llvm/CodeGen/SelectionDAG.h"
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@ -95,6 +96,9 @@ StatepointLoweringState::allocateStackSlot(EVT ValueType,
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SDValue SpillSlot = Builder.DAG.CreateStackTemporary(ValueType);
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const unsigned FI = cast<FrameIndexSDNode>(SpillSlot)->getIndex();
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auto *MFI = Builder.DAG.getMachineFunction().getFrameInfo();
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MFI->markAsStatepointSpillSlotObjectIndex(FI);
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Builder.FuncInfo.StatepointStackSlots.push_back(FI);
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AllocatedStackSlots.push_back(true);
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return SpillSlot;
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@ -1094,6 +1094,19 @@ MachineBasicBlock*
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TargetLoweringBase::emitPatchPoint(MachineInstr *MI,
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MachineBasicBlock *MBB) const {
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MachineFunction &MF = *MI->getParent()->getParent();
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MachineFrameInfo &MFI = *MF.getFrameInfo();
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// We're handling multiple types of operands here:
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// PATCHPOINT MetaArgs - live-in, read only, direct
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// STATEPOINT Deopt Spill - live-through, read only, indirect
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// STATEPOINT Deopt Alloca - live-through, read only, direct
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// (We're currently conservative and mark the deopt slots read/write in
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// practice.)
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// STATEPOINT GC Spill - live-through, read/write, indirect
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// STATEPOINT GC Alloca - live-through, read/write, direct
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// The live-in vs live-through is handled already (the live through ones are
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// all stack slots), but we need to handle the different type of stackmap
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// operands and memory effects here.
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// MI changes inside this loop as we grow operands.
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for(unsigned OperIdx = 0; OperIdx != MI->getNumOperands(); ++OperIdx) {
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@ -1109,10 +1122,24 @@ TargetLoweringBase::emitPatchPoint(MachineInstr *MI,
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// Copy operands before the frame-index.
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for (unsigned i = 0; i < OperIdx; ++i)
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MIB.addOperand(MI->getOperand(i));
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// Add frame index operands: direct-mem-ref tag, #FI, offset.
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MIB.addImm(StackMaps::DirectMemRefOp);
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MIB.addOperand(MI->getOperand(OperIdx));
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MIB.addImm(0);
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// Add frame index operands recognized by stackmaps.cpp
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if (MFI.isStatepointSpillSlotObjectIndex(FI)) {
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// indirect-mem-ref tag, size, #FI, offset.
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// Used for spills inserted by StatepointLowering. This codepath is not
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// used for patchpoints/stackmaps at all, for these spilling is done via
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// foldMemoryOperand callback only.
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assert(MI->getOpcode() == TargetOpcode::STATEPOINT && "sanity");
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MIB.addImm(StackMaps::IndirectMemRefOp);
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MIB.addImm(MFI.getObjectSize(FI));
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MIB.addOperand(MI->getOperand(OperIdx));
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MIB.addImm(0);
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} else {
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// direct-mem-ref tag, #FI, offset.
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// Used by patchpoint, and direct alloca arguments to statepoints
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MIB.addImm(StackMaps::DirectMemRefOp);
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MIB.addOperand(MI->getOperand(OperIdx));
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MIB.addImm(0);
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}
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// Copy the operands after the frame index.
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for (unsigned i = OperIdx + 1; i != MI->getNumOperands(); ++i)
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MIB.addOperand(MI->getOperand(i));
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@ -1122,7 +1149,6 @@ TargetLoweringBase::emitPatchPoint(MachineInstr *MI,
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assert(MIB->mayLoad() && "Folded a stackmap use to a non-load!");
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// Add a new memory operand for this FI.
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const MachineFrameInfo &MFI = *MF.getFrameInfo();
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assert(MFI.getObjectOffset(FI) != -1);
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unsigned Flags = MachineMemOperand::MOLoad;
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@ -11,7 +11,7 @@ declare zeroext i1 @return_i1()
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define i1 @test(i32 addrspace(1)* %ptr_base, i32 %arg)
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gc "statepoint-example" {
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; CHECK-LABEL: test
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; CHECK-LABEL: test:
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; Do we see two spills for the local values and the store to the
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; alloca?
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; CHECK: subq $40, %rsp
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@ -94,18 +94,19 @@ declare i32 addrspace(1)* @llvm.experimental.gc.relocate.p1i32(i32, i32, i32) #3
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; CHECK-NEXT: .quad 40
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; CHECK-NEXT: .quad test_derived_arg
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; CHECK-NEXT: .quad 40
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; CHECK-NEXT: .quad test_id
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; CHECK-NEXT: .quad 8
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;
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; test
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;
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; Large Constants
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; Statepoint ID only
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; CHECK: .quad 0
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; Statepoint ID
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; CHECK-NEXT: .quad 0
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; Callsites
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; Constant arguments
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; CHECK: .long .Ltmp1-test
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; CHECK-NEXT: .long .Ltmp1-test
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; CHECK: .short 0
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; CHECK: .short 11
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; SmallConstant (0)
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@ -123,8 +124,8 @@ declare i32 addrspace(1)* @llvm.experimental.gc.relocate.p1i32(i32, i32, i32) #3
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; CHECK: .byte 8
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; CHECK: .short 0
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; CHECK: .long 2
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; Direct Spill Slot [RSP+0]
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; CHECK: .byte 2
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; Indirect Spill Slot [RSP+0]
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; CHECK: .byte 3
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; CHECK: .byte 8
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; CHECK: .short 7
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; CHECK: .long 16
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@ -143,23 +144,23 @@ declare i32 addrspace(1)* @llvm.experimental.gc.relocate.p1i32(i32, i32, i32) #3
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; CHECK: .byte 8
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; CHECK: .short 0
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; CHECK: .long 0
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; Direct Spill Slot [RSP+16]
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; CHECK: .byte 2
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; Indirect Spill Slot [RSP+16]
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; CHECK: .byte 3
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; CHECK: .byte 8
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; CHECK: .short 7
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; CHECK: .long 16
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; Direct Spill Slot [RSP+8]
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; CHECK: .byte 2
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; Indirect Spill Slot [RSP+8]
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; CHECK: .byte 3
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; CHECK: .byte 8
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; CHECK: .short 7
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; CHECK: .long 8
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; Direct Spill Slot [RSP+16]
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; CHECK: .byte 2
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; Indirect Spill Slot [RSP+16]
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; CHECK: .byte 3
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; CHECK: .byte 8
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; CHECK: .short 7
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; CHECK: .long 16
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; Direct Spill Slot [RSP+16]
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; CHECK: .byte 2
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; Indirect Spill Slot [RSP+16]
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; CHECK: .byte 3
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; CHECK: .byte 8
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; CHECK: .short 7
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; CHECK: .long 16
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@ -171,15 +172,13 @@ declare i32 addrspace(1)* @llvm.experimental.gc.relocate.p1i32(i32, i32, i32) #3
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;
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; test_derived_arg
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;
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; Large Constants
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; Statepoint ID only
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; CHECK: .quad 0
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; Statepoint ID
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; CHECK-NEXT: .quad 0
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; Callsites
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; Constant arguments
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; CHECK: .long .Ltmp3-test_derived_arg
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; CHECK-NEXT: .long .Ltmp3-test_derived_arg
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; CHECK: .short 0
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; CHECK: .short 11
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; SmallConstant (0)
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@ -192,8 +191,8 @@ declare i32 addrspace(1)* @llvm.experimental.gc.relocate.p1i32(i32, i32, i32) #3
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; CHECK: .byte 8
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; CHECK: .short 0
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; CHECK: .long 2
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; Direct Spill Slot [RSP+0]
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; CHECK: .byte 2
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; Indirect Spill Slot [RSP+0]
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; CHECK: .byte 3
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; CHECK: .byte 8
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; CHECK: .short 7
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; CHECK: .long 16
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@ -212,23 +211,23 @@ declare i32 addrspace(1)* @llvm.experimental.gc.relocate.p1i32(i32, i32, i32) #3
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; CHECK: .byte 8
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; CHECK: .short 0
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; CHECK: .long 0
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; Direct Spill Slot [RSP+16]
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; CHECK: .byte 2
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; Indirect Spill Slot [RSP+16]
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; CHECK: .byte 3
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; CHECK: .byte 8
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; CHECK: .short 7
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; CHECK: .long 16
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; Direct Spill Slot [RSP+8]
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; CHECK: .byte 2
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; Indirect Spill Slot [RSP+8]
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; CHECK: .byte 3
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; CHECK: .byte 8
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; CHECK: .short 7
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; CHECK: .long 8
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; Direct Spill Slot [RSP+16]
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; CHECK: .byte 2
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; Indirect Spill Slot [RSP+16]
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; CHECK: .byte 3
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; CHECK: .byte 8
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; CHECK: .short 7
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; CHECK: .long 16
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; Direct Spill Slot [RSP+16]
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; CHECK: .byte 2
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; Indirect Spill Slot [RSP+16]
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; CHECK: .byte 3
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; CHECK: .byte 8
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; CHECK: .short 7
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; CHECK: .long 16
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@ -239,13 +238,12 @@ declare i32 addrspace(1)* @llvm.experimental.gc.relocate.p1i32(i32, i32, i32) #3
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; CHECK: .align 8
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; Records for the test_id function:
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; No large constants
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; The Statepoint ID:
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; CHECK: .quad 237
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; CHECK-NEXT: .quad 237
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; Instruction Offset
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; CHECK: .long .Ltmp5-test_id
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; CHECK-NEXT: .long .Ltmp5-test_id
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; Reserved:
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; CHECK: .short 0
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