Subzero: Fix over-aggressive bool folding.

src/IceInst.h

Index: src/IceInst.h
diff --git a/src/IceInst.h b/src/IceInst.h
index db273aa500c7f17e8eadb38bae559aaabe9d7a8c..0ce267ff07793fe334de3183eb0f5ae8c81f9047 100644
--- a/src/IceInst.h
+++ b/src/IceInst.h
@@ -135,6 +135,13 @@ public:
   /// "var_dest=var_src" assignment where the dest and src are both variables.
   virtual bool isVarAssign() const { return false; }
 
+  /// Returns true if the instruction has a possible side effect of changing
+  /// memory, in which case a memory load should not be reordered with respect
+  /// to this instruction.  It should really be pure virtual, but we can't
+  /// because of g++ and llvm::ilist<>, so we implement it as
+  /// report_fatal_error().
+  virtual bool isMemoryWrite() const;
+
   void livenessLightweight(Cfg *Func, LivenessBV &Live);
   /// Calculates liveness for this instruction. Returns true if this instruction
   /// is (tentatively) still live and should be retained, and false if this
@@ -259,6 +266,7 @@ public:
   Operand *getSizeInBytes() const { return getSrc(0); }
   bool getKnownFrameOffset() const { return KnownFrameOffset; }
   void setKnownFrameOffset() { KnownFrameOffset = true; }
+  bool isMemoryWrite() const override { return false; }
   void dump(const Cfg *Func) const override;
   static bool classof(const Inst *Instr) { return Instr->getKind() == Alloca; }
 
@@ -296,6 +304,7 @@ public:
 
   static const char *getOpName(OpKind Op);
   bool isCommutative() const;
+  bool isMemoryWrite() const override { return false; }
   void dump(const Cfg *Func) const override;
   static bool classof(const Inst *Instr) {
     return Instr->getKind() == Arithmetic;
@@ -323,6 +332,7 @@ public:
     return new (Func->allocate<InstAssign>()) InstAssign(Func, Dest, Source);
   }
   bool isVarAssign() const override;
+  bool isMemoryWrite() const override { return false; }
   void dump(const Cfg *Func) const override;
   static bool classof(const Inst *Instr) { return Instr->getKind() == Assign; }
 
@@ -363,6 +373,7 @@ public:
   NodeList getTerminatorEdges() const override;
   bool isUnconditionalBranch() const override { return isUnconditional(); }
   bool repointEdges(CfgNode *OldNode, CfgNode *NewNode) override;
+  bool isMemoryWrite() const override { return false; }
   void dump(const Cfg *Func) const override;
   static bool classof(const Inst *Instr) { return Instr->getKind() == Br; }
 
@@ -402,6 +413,7 @@ public:
   SizeT getNumArgs() const { return getSrcSize() - 1; }
   bool isTailcall() const { return HasTailCall; }
   bool isTargetHelperCall() const { return IsTargetHelperCall; }
+  bool isMemoryWrite() const override { return true; }
   void dump(const Cfg *Func) const override;
   static bool classof(const Inst *Instr) { return Instr->getKind() == Call; }
   Type getReturnType() const;
@@ -443,6 +455,7 @@ public:
         InstCast(Func, CastKind, Dest, Source);
   }
   OpKind getCastKind() const { return CastKind; }
+  bool isMemoryWrite() const override { return false; }
   void dump(const Cfg *Func) const override;
   static bool classof(const Inst *Instr) { return Instr->getKind() == Cast; }
 
@@ -465,6 +478,7 @@ public:
         InstExtractElement(Func, Dest, Source1, Source2);
   }
 
+  bool isMemoryWrite() const override { return false; }
   void dump(const Cfg *Func) const override;
   static bool classof(const Inst *Instr) {
     return Instr->getKind() == ExtractElement;
@@ -496,6 +510,7 @@ public:
         InstFcmp(Func, Condition, Dest, Source1, Source2);
   }
   FCond getCondition() const { return Condition; }
+  bool isMemoryWrite() const override { return false; }
   void dump(const Cfg *Func) const override;
   static bool classof(const Inst *Instr) { return Instr->getKind() == Fcmp; }
 
@@ -527,6 +542,7 @@ public:
         InstIcmp(Func, Condition, Dest, Source1, Source2);
   }
   ICond getCondition() const { return Condition; }
+  bool isMemoryWrite() const override { return false; }
   void dump(const Cfg *Func) const override;
   static bool classof(const Inst *Instr) { return Instr->getKind() == Icmp; }
 
@@ -550,6 +566,7 @@ public:
         InstInsertElement(Func, Dest, Source1, Source2, Source3);
   }
 
+  bool isMemoryWrite() const override { return false; }
   void dump(const Cfg *Func) const override;
   static bool classof(const Inst *Instr) {
     return Instr->getKind() == InsertElement;
@@ -579,6 +596,9 @@ public:
   }
 
   Intrinsics::IntrinsicInfo getIntrinsicInfo() const { return Info; }
+  bool isMemoryWrite() const override {
+    return getIntrinsicInfo().IsMemoryWrite;
+  }
 
 private:
   InstIntrinsicCall(Cfg *Func, SizeT NumArgs, Variable *Dest,
@@ -604,6 +624,7 @@ public:
     return new (Func->allocate<InstLoad>()) InstLoad(Func, Dest, SourceAddr);
   }
   Operand *getSourceAddress() const { return getSrc(0); }
+  bool isMemoryWrite() const override { return false; }
   void dump(const Cfg *Func) const override;
   static bool classof(const Inst *Instr) { return Instr->getKind() == Load; }
 
@@ -630,6 +651,7 @@ public:
   void livenessPhiOperand(LivenessBV &Live, CfgNode *Target,
                           Liveness *Liveness);
   Inst *lower(Cfg *Func);
+  bool isMemoryWrite() const override { return false; }
   void dump(const Cfg *Func) const override;
   static bool classof(const Inst *Instr) { return Instr->getKind() == Phi; }
 
@@ -664,6 +686,7 @@ public:
     return getSrc(0);
   }
   NodeList getTerminatorEdges() const override { return NodeList(); }
+  bool isMemoryWrite() const override { return false; }
   void dump(const Cfg *Func) const override;
   static bool classof(const Inst *Instr) { return Instr->getKind() == Ret; }
 
@@ -686,6 +709,7 @@ public:
   Operand *getCondition() const { return getSrc(0); }
   Operand *getTrueOperand() const { return getSrc(1); }
   Operand *getFalseOperand() const { return getSrc(2); }
+  bool isMemoryWrite() const override { return false; }
   void dump(const Cfg *Func) const override;
   static bool classof(const Inst *Instr) { return Instr->getKind() == Select; }
 
@@ -712,6 +736,7 @@ public:
   Operand *getData() const { return getSrc(0); }
   Variable *getRmwBeacon() const;
   void setRmwBeacon(Variable *Beacon);
+  bool isMemoryWrite() const override { return true; }
   void dump(const Cfg *Func) const override;
   static bool classof(const Inst *Instr) { return Instr->getKind() == Store; }
 
@@ -745,6 +770,7 @@ public:
   void addBranch(SizeT CaseIndex, uint64_t Value, CfgNode *Label);
   NodeList getTerminatorEdges() const override;
   bool repointEdges(CfgNode *OldNode, CfgNode *NewNode) override;
+  bool isMemoryWrite() const override { return false; }
   void dump(const Cfg *Func) const override;
   static bool classof(const Inst *Instr) { return Instr->getKind() == Switch; }
 
@@ -773,6 +799,7 @@ public:
     return new (Func->allocate<InstUnreachable>()) InstUnreachable(Func);
   }
   NodeList getTerminatorEdges() const override { return NodeList(); }
+  bool isMemoryWrite() const override { return false; }
   void dump(const Cfg *Func) const override;
   static bool classof(const Inst *Instr) {
     return Instr->getKind() == Unreachable;
@@ -797,6 +824,7 @@ public:
   }
   void emit(const Cfg *Func) const override;
   void emitIAS(const Cfg * /* Func */) const override {}
+  bool isMemoryWrite() const override { return false; }
   void dump(const Cfg *Func) const override;
   Option getOption() const { return BundleOption; }
   static bool classof(const Inst *Instr) {
@@ -820,6 +848,7 @@ public:
   }
   void emit(const Cfg *Func) const override;
   void emitIAS(const Cfg * /* Func */) const override {}
+  bool isMemoryWrite() const override { return false; }
   void dump(const Cfg *Func) const override;
   static bool classof(const Inst *Instr) {
     return Instr->getKind() == BundleUnlock;
@@ -852,6 +881,7 @@ public:
   }
   void emit(const Cfg *Func) const override;
   void emitIAS(const Cfg * /* Func */) const override {}
+  bool isMemoryWrite() const override { return false; }
   void dump(const Cfg *Func) const override;
   static bool classof(const Inst *Instr) { return Instr->getKind() == FakeDef; }
 
@@ -877,6 +907,7 @@ public:
   }
   void emit(const Cfg *Func) const override;
   void emitIAS(const Cfg * /* Func */) const override {}
+  bool isMemoryWrite() const override { return false; }
   void dump(const Cfg *Func) const override;
   static bool classof(const Inst *Instr) { return Instr->getKind() == FakeUse; }
 
@@ -905,6 +936,7 @@ public:
   const Inst *getLinked() const { return Linked; }
   void emit(const Cfg *Func) const override;
   void emitIAS(const Cfg * /* Func */) const override {}
+  bool isMemoryWrite() const override { return false; }
   void dump(const Cfg *Func) const override;
   static bool classof(const Inst *Instr) {
     return Instr->getKind() == FakeKill;
@@ -941,6 +973,7 @@ public:
     assert(I < NumTargets);
     return Targets[I];
   }
+  bool isMemoryWrite() const override { return false; }
   void dump(const Cfg *Func) const override;
   static bool classof(const Inst *Instr) {
     return Instr->getKind() == JumpTable;
@@ -988,7 +1021,8 @@ public:
   InstBreakpoint(const InstBreakpoint &) = delete;
   InstBreakpoint &operator=(const InstBreakpoint &) = delete;
 
-  InstBreakpoint(Cfg *Func);
+  explicit InstBreakpoint(Cfg *Func);
+  bool isMemoryWrite() const override { return false; }
 
 public:
   static InstBreakpoint *create(Cfg *Func) {
@@ -1009,6 +1043,9 @@ class InstTarget : public Inst {
 
 public:
   uint32_t getEmitInstCount() const override { return 1; }
+  bool isMemoryWrite() const override {
+    return true; // conservative answer
+  }
   void dump(const Cfg *Func) const override;
   static bool classof(const Inst *Instr) { return Instr->getKind() >= Target; }