[patchpoint] Add support for symbolic patchpoint targets to SelectionDAG and the

X86 backend.

The code generated for symbolic targets is identical to the code generated for
constant targets, except that a relocation is emitted to fix up the actual
target address at link-time. This allows IR and object files containing
patchpoints to be cached across JIT-invocations where the target address may
change.

llvm-svn: 235483

llvm/include/llvm/MC/MCInstBuilder.h

@@ -58,6 +58,12 @@ public:
     return *this;
   }
 
+  /// \brief Add an operand.
+  MCInstBuilder &addOperand(const MCOperand &Op) {
+    Inst.addOperand(Op);
+    return *this;
+  }
+
   operator MCInst&() {
     return Inst;
   }

llvm/lib/CodeGen/SelectionDAG/FastISel.cpp

@@ -711,7 +711,7 @@ bool FastISel::selectPatchpoint(const CallInst *I) {
   CallingConv::ID CC = I->getCallingConv();
   bool IsAnyRegCC = CC == CallingConv::AnyReg;
   bool HasDef = !I->getType()->isVoidTy();
-  Value *Callee = I->getOperand(PatchPointOpers::TargetPos);
+  Value *Callee = I->getOperand(PatchPointOpers::TargetPos)->stripPointerCasts();
 
   // Get the real number of arguments participating in the call <numArgs>
   assert(isa<ConstantInt>(I->getOperand(PatchPointOpers::NArgPos)) &&
@@ -757,23 +757,25 @@ bool FastISel::selectPatchpoint(const CallInst *I) {
       cast<ConstantInt>(I->getOperand(PatchPointOpers::NBytesPos));
   Ops.push_back(MachineOperand::CreateImm(NumBytes->getZExtValue()));
 
-  // Assume that the callee is a constant address or null pointer.
-  // FIXME: handle function symbols in the future.
-  uint64_t CalleeAddr;
-  if (const auto *C = dyn_cast<IntToPtrInst>(Callee))
-    CalleeAddr = cast<ConstantInt>(C->getOperand(0))->getZExtValue();
-  else if (const auto *C = dyn_cast<ConstantExpr>(Callee)) {
-    if (C->getOpcode() == Instruction::IntToPtr)
-      CalleeAddr = cast<ConstantInt>(C->getOperand(0))->getZExtValue();
-    else
+  // Add the call target.
+  if (const auto *C = dyn_cast<IntToPtrInst>(Callee)) {
+    uint64_t CalleeConstAddr =
+      cast<ConstantInt>(C->getOperand(0))->getZExtValue();
+    Ops.push_back(MachineOperand::CreateImm(CalleeConstAddr));
+  } else if (const auto *C = dyn_cast<ConstantExpr>(Callee)) {
+    if (C->getOpcode() == Instruction::IntToPtr) {
+      uint64_t CalleeConstAddr =
+        cast<ConstantInt>(C->getOperand(0))->getZExtValue();
+      Ops.push_back(MachineOperand::CreateImm(CalleeConstAddr));
+    } else
       llvm_unreachable("Unsupported ConstantExpr.");
+  } else if (const auto *GV = dyn_cast<GlobalValue>(Callee)) {
+    Ops.push_back(MachineOperand::CreateGA(GV, 0));
   } else if (isa<ConstantPointerNull>(Callee))
-    CalleeAddr = 0;
+    Ops.push_back(MachineOperand::CreateImm(0));
   else
     llvm_unreachable("Unsupported callee address.");
 
-  Ops.push_back(MachineOperand::CreateImm(CalleeAddr));
-
   // Adjust <numArgs> to account for any arguments that have been passed on
   // the stack instead.
   unsigned NumCallRegArgs = IsAnyRegCC ? NumArgs : CLI.OutRegs.size();

llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp

@@ -7001,7 +7001,16 @@ void SelectionDAGBuilder::visitPatchpoint(ImmutableCallSite CS,
   CallingConv::ID CC = CS.getCallingConv();
   bool IsAnyRegCC = CC == CallingConv::AnyReg;
   bool HasDef = !CS->getType()->isVoidTy();
-  SDValue Callee = getValue(CS->getOperand(2)); // <target>
+  SDValue Callee = getValue(CS->getOperand(PatchPointOpers::TargetPos));
+
+  // Handle immediate and symbolic callees.
+  if (auto* ConstCallee = dyn_cast<ConstantSDNode>(Callee))
+    Callee = DAG.getIntPtrConstant(ConstCallee->getZExtValue(),
+                                   /*isTarget=*/true);
+  else if (auto* SymbolicCallee = dyn_cast<GlobalAddressSDNode>(Callee))
+    Callee =  DAG.getTargetGlobalAddress(SymbolicCallee->getGlobal(),
+                                         SDLoc(SymbolicCallee),
+                                         SymbolicCallee->getValueType(0));
 
   // Get the real number of arguments participating in the call <numArgs>
   SDValue NArgVal = getValue(CS.getArgument(PatchPointOpers::NArgPos));
@@ -7041,11 +7050,8 @@ void SelectionDAGBuilder::visitPatchpoint(ImmutableCallSite CS,
   Ops.push_back(DAG.getTargetConstant(
                   cast<ConstantSDNode>(NBytesVal)->getZExtValue(), MVT::i32));
 
-  // Assume that the Callee is a constant address.
-  // FIXME: handle function symbols in the future.
-  Ops.push_back(
-    DAG.getIntPtrConstant(cast<ConstantSDNode>(Callee)->getZExtValue(),
-                          /*isTarget=*/true));
+  // Add the callee.
+  Ops.push_back(Callee);
 
   // Adjust <numArgs> to account for any arguments that have been passed on the
   // stack instead.

llvm/lib/Target/X86/X86AsmPrinter.h

@@ -81,7 +81,7 @@ class LLVM_LIBRARY_VISIBILITY X86AsmPrinter : public AsmPrinter {
 
   void InsertStackMapShadows(MachineFunction &MF);
   void LowerSTACKMAP(const MachineInstr &MI);
-  void LowerPATCHPOINT(const MachineInstr &MI);
+  void LowerPATCHPOINT(const MachineInstr &MI, X86MCInstLower &MCIL);
 
   void LowerTlsAddr(X86MCInstLower &MCInstLowering, const MachineInstr &MI);
 

llvm/lib/Target/X86/X86MCInstLower.cpp

@@ -867,7 +867,8 @@ void X86AsmPrinter::LowerSTACKMAP(const MachineInstr &MI) {
 
 // Lower a patchpoint of the form:
 // [<def>], <id>, <numBytes>, <target>, <numArgs>, <cc>, ...
-void X86AsmPrinter::LowerPATCHPOINT(const MachineInstr &MI) {
+void X86AsmPrinter::LowerPATCHPOINT(const MachineInstr &MI,
+                                    X86MCInstLower &MCIL) {
   assert(Subtarget->is64Bit() && "Patchpoint currently only supports X86-64");
 
   SMShadowTracker.emitShadowPadding(OutStreamer, getSubtargetInfo());
@@ -877,8 +878,29 @@ void X86AsmPrinter::LowerPATCHPOINT(const MachineInstr &MI) {
   PatchPointOpers opers(&MI);
   unsigned ScratchIdx = opers.getNextScratchIdx();
   unsigned EncodedBytes = 0;
-  int64_t CallTarget = opers.getMetaOper(PatchPointOpers::TargetPos).getImm();
-  if (CallTarget) {
+  const MachineOperand &CalleeMO =
+    opers.getMetaOper(PatchPointOpers::TargetPos);
+
+  // Check for null target. If target is non-null (i.e. is non-zero or is
+  // symbolic) then emit a call.
+  if (!(CalleeMO.isImm() && !CalleeMO.getImm())) {
+    MCOperand CalleeMCOp;
+    switch (CalleeMO.getType()) {
+    default:
+      /// FIXME: Add a verifier check for bad callee types.
+      llvm_unreachable("Unrecognized callee operand type.");
+    case MachineOperand::MO_Immediate:
+      if (CalleeMO.getImm())
+        CalleeMCOp = MCOperand::CreateImm(CalleeMO.getImm());
+      break;
+    case MachineOperand::MO_ExternalSymbol:
+    case MachineOperand::MO_GlobalAddress:
+      CalleeMCOp =
+        MCIL.LowerSymbolOperand(CalleeMO,
+                                MCIL.GetSymbolFromOperand(CalleeMO));
+      break;
+    }
+
     // Emit MOV to materialize the target address and the CALL to target.
     // This is encoded with 12-13 bytes, depending on which register is used.
     unsigned ScratchReg = MI.getOperand(ScratchIdx).getReg();
@@ -886,10 +908,12 @@ void X86AsmPrinter::LowerPATCHPOINT(const MachineInstr &MI) {
       EncodedBytes = 13;
     else
       EncodedBytes = 12;
-    EmitAndCountInstruction(MCInstBuilder(X86::MOV64ri).addReg(ScratchReg)
-                                                       .addImm(CallTarget));
+
+    EmitAndCountInstruction(
+        MCInstBuilder(X86::MOV64ri).addReg(ScratchReg).addOperand(CalleeMCOp));
     EmitAndCountInstruction(MCInstBuilder(X86::CALL64r).addReg(ScratchReg));
   }
+
   // Emit padding.
   unsigned NumBytes = opers.getMetaOper(PatchPointOpers::NBytesPos).getImm();
   assert(NumBytes >= EncodedBytes &&
@@ -1091,7 +1115,7 @@ void X86AsmPrinter::EmitInstruction(const MachineInstr *MI) {
     return LowerSTACKMAP(*MI);
 
   case TargetOpcode::PATCHPOINT:
-    return LowerPATCHPOINT(*MI);
+    return LowerPATCHPOINT(*MI, MCInstLowering);
 
   case X86::MORESTACK_RET:
     EmitAndCountInstruction(MCInstBuilder(getRetOpcode(*Subtarget)));

llvm/test/CodeGen/X86/patchpoint.ll

@@ -21,6 +21,22 @@ entry:
   ret i64 %result
 }
 
+; Trivial symbolic patchpoint codegen.
+;
+
+declare i64 @foo(i64 %p1, i64 %p2)
+define i64 @trivial_symbolic_patchpoint_codegen(i64 %p1, i64 %p2) {
+entry:
+; CHECK-LABEL: trivial_symbolic_patchpoint_codegen:
+; CHECK:       movabsq $_foo, %r11
+; CHECK-NEXT:  callq   *%r11
+; CHECK-NEXT:  xchgw   %ax, %ax
+; CHECK:       retq
+  %result = tail call i64 (i64, i32, i8*, i32, ...) @llvm.experimental.patchpoint.i64(i64 9, i32 15, i8* bitcast (i64 (i64, i64)* @foo to i8*), i32 2, i64 %p1, i64 %p2)
+  ret i64 %result
+}
+
+
 ; Caller frame metadata with stackmaps. This should not be optimized
 ; as a leaf function.
 ;