[ImplicitNullCheck] Extend Implicit Null Check scope by using stores

Summary:
This change allows usage of store instruction for implicit null check.

Memory Aliasing Analisys is not used and change conservatively supposes
that any store and load may access the same memory. As a result
re-ordering of store-store, store-load and load-store is prohibited.

Patch by Serguei Katkov!

Reviewers: reames, sanjoy

Reviewed By: sanjoy

Subscribers: atrick, llvm-commits

Differential Revision: https://reviews.llvm.org/D29400

llvm-svn: 294338

2 files changed, 24 insertions, 20 deletions

diff --git a/llvm/lib/Target/X86/X86AsmPrinter.h b/llvm/lib/Target/X86/X86AsmPrinter.h
index bb15fd7ae8e..44bc373b039 100644
--- a/llvm/lib/Target/X86/X86AsmPrinter.h
+++ b/llvm/lib/Target/X86/X86AsmPrinter.h
@@ -81,7 +81,7 @@ class LLVM_LIBRARY_VISIBILITY X86AsmPrinter : public AsmPrinter {
   void LowerSTACKMAP(const MachineInstr &MI);
   void LowerPATCHPOINT(const MachineInstr &MI, X86MCInstLower &MCIL);
   void LowerSTATEPOINT(const MachineInstr &MI, X86MCInstLower &MCIL);
-  void LowerFAULTING_LOAD_OP(const MachineInstr &MI, X86MCInstLower &MCIL);
+  void LowerFAULTING_OP(const MachineInstr &MI, X86MCInstLower &MCIL);
   void LowerPATCHABLE_OP(const MachineInstr &MI, X86MCInstLower &MCIL);
 
   void LowerTlsAddr(X86MCInstLower &MCInstLowering, const MachineInstr &MI);
diff --git a/llvm/lib/Target/X86/X86MCInstLower.cpp b/llvm/lib/Target/X86/X86MCInstLower.cpp
index fd4626c494e..65949531126 100644
--- a/llvm/lib/Target/X86/X86MCInstLower.cpp
+++ b/llvm/lib/Target/X86/X86MCInstLower.cpp
@@ -894,30 +894,34 @@ void X86AsmPrinter::LowerSTATEPOINT(const MachineInstr &MI,
   SM.recordStatepoint(MI);
 }
 
-void X86AsmPrinter::LowerFAULTING_LOAD_OP(const MachineInstr &MI,
-                                       X86MCInstLower &MCIL) {
-  // FAULTING_LOAD_OP <def>, <MBB handler>, <load opcode>, <load operands>
+void X86AsmPrinter::LowerFAULTING_OP(const MachineInstr &FaultingMI,
+                                     X86MCInstLower &MCIL) {
+  // FAULTING_LOAD_OP <def>, <faltinf type>, <MBB handler>,
+  //                  <opcode>, <operands>
 
-  unsigned LoadDefRegister = MI.getOperand(0).getReg();
-  MCSymbol *HandlerLabel = MI.getOperand(1).getMBB()->getSymbol();
-  unsigned LoadOpcode = MI.getOperand(2).getImm();
-  unsigned LoadOperandsBeginIdx = 3;
+  unsigned DefRegister = FaultingMI.getOperand(0).getReg();
+  FaultMaps::FaultKind FK =
+      static_cast<FaultMaps::FaultKind>(FaultingMI.getOperand(1).getImm());
+  MCSymbol *HandlerLabel = FaultingMI.getOperand(2).getMBB()->getSymbol();
+  unsigned Opcode = FaultingMI.getOperand(3).getImm();
+  unsigned OperandsBeginIdx = 4;
 
-  FM.recordFaultingOp(FaultMaps::FaultingLoad, HandlerLabel);
+  assert(FK < FaultMaps::FaultKindMax && "Invalid Faulting Kind!");
+  FM.recordFaultingOp(FK, HandlerLabel);
 
-  MCInst LoadMI;
-  LoadMI.setOpcode(LoadOpcode);
+  MCInst MI;
+  MI.setOpcode(Opcode);
 
-  if (LoadDefRegister != X86::NoRegister)
-    LoadMI.addOperand(MCOperand::createReg(LoadDefRegister));
+  if (DefRegister != X86::NoRegister)
+    MI.addOperand(MCOperand::createReg(DefRegister));
 
-  for (auto I = MI.operands_begin() + LoadOperandsBeginIdx,
-            E = MI.operands_end();
+  for (auto I = FaultingMI.operands_begin() + OperandsBeginIdx,
+            E = FaultingMI.operands_end();
        I != E; ++I)
-    if (auto MaybeOperand = MCIL.LowerMachineOperand(&MI, *I))
-      LoadMI.addOperand(MaybeOperand.getValue());
+    if (auto MaybeOperand = MCIL.LowerMachineOperand(&FaultingMI, *I))
+      MI.addOperand(MaybeOperand.getValue());
 
-  OutStreamer->EmitInstruction(LoadMI, getSubtargetInfo());
+  OutStreamer->EmitInstruction(MI, getSubtargetInfo());
 }
 
 void X86AsmPrinter::LowerFENTRY_CALL(const MachineInstr &MI,
@@ -1388,8 +1392,8 @@ void X86AsmPrinter::EmitInstruction(const MachineInstr *MI) {
   case TargetOpcode::STATEPOINT:
     return LowerSTATEPOINT(*MI, MCInstLowering);
 
-  case TargetOpcode::FAULTING_LOAD_OP:
-    return LowerFAULTING_LOAD_OP(*MI, MCInstLowering);
+  case TargetOpcode::FAULTING_OP:
+    return LowerFAULTING_OP(*MI, MCInstLowering);
 
   case TargetOpcode::FENTRY_CALL:
     return LowerFENTRY_CALL(*MI, MCInstLowering);