Subzero. Enable Atomics in ARM.

src/IceTargetLoweringARM32.h

Index: src/IceTargetLoweringARM32.h
diff --git a/src/IceTargetLoweringARM32.h b/src/IceTargetLoweringARM32.h
index 83d2fafe807aa71af7cd2a5bbf35c6fdecb45880..8a46049351a26b4fd3471466e8bc9c028bd41d3a 100644
--- a/src/IceTargetLoweringARM32.h
+++ b/src/IceTargetLoweringARM32.h
@@ -131,6 +131,8 @@ protected:
   void lowerExtractElement(const InstExtractElement *Inst) override;
   void lowerFcmp(const InstFcmp *Inst) override;
   void lowerIcmp(const InstIcmp *Inst) override;
+  void lowerAtomicRMW(Variable *Dest, uint32_t Operation, Operand *Ptr,
+                      Operand *Val);
   void lowerIntrinsicCall(const InstIntrinsicCall *Inst) override;
   void lowerInsertElement(const InstInsertElement *Inst) override;
   void lowerLoad(const InstLoad *Inst) override;
@@ -160,6 +162,7 @@ protected:
   Variable *legalizeToReg(Operand *From, int32_t RegNum = Variable::NoRegister);
   OperandARM32Mem *formMemoryOperand(Operand *Ptr, Type Ty);
 
+  Variable64On32 *makeI64RegPair();
   Variable *makeReg(Type Ty, int32_t RegNum = Variable::NoRegister);
   static Type stackSlotType();
   Variable *copyToReg(Operand *Src, int32_t RegNum = Variable::NoRegister);
@@ -255,13 +258,13 @@ protected:
     Context.insert(InstARM32Ldr::create(Func, Dest, Addr, Pred));
   }
   void _ldrex(Variable *Dest, OperandARM32Mem *Addr,
-             CondARM32::Cond Pred = CondARM32::AL) {
-   Context.insert(InstARM32Ldrex::create(Func, Dest, Addr, Pred));
-   if (auto *Dest64 = llvm::dyn_cast<Variable64On32>(Dest)) {
-     Context.insert(InstFakeDef::create(Func, Dest64->getLo(), Dest));
-     Context.insert(InstFakeDef::create(Func, Dest64->getHi(), Dest));
-   }
- }
+              CondARM32::Cond Pred = CondARM32::AL) {
+    Context.insert(InstARM32Ldrex::create(Func, Dest, Addr, Pred));
+    if (auto *Dest64 = llvm::dyn_cast<Variable64On32>(Dest)) {
+      Context.insert(InstFakeDef::create(Func, Dest64->getLo(), Dest));
+      Context.insert(InstFakeDef::create(Func, Dest64->getHi(), Dest));
+    }
+  }
   void _lsl(Variable *Dest, Variable *Src0, Operand *Src1,
             CondARM32::Cond Pred = CondARM32::AL) {
     Context.insert(InstARM32Lsl::create(Func, Dest, Src0, Src1, Pred));
@@ -299,6 +302,7 @@ protected:
       Context.insert(InstFakeDef::create(Func, Instr->getDestHi()));
     }
   }
+
   void _mov_redefined(Variable *Dest, Operand *Src0,
                       CondARM32::Cond Pred = CondARM32::AL) {
     auto *Instr = InstARM32Mov::create(Func, Dest, Src0, Pred);
@@ -385,11 +389,17 @@ protected:
   }
   void _strex(Variable *Dest, Variable *Value, OperandARM32Mem *Addr,
               CondARM32::Cond Pred = CondARM32::AL) {
+    // strex requires Dest to be a register other than Value or Addr. This
+    // restriction is cleanly represented by adding an "early definition of of

[Jim Stichnoth, 2015/10/05 22:07:06]

s/of of/of/
Also, should the double-quote be there?  (It's missing the closing
double-quote.)

[John, 2015/10/06 12:03:38]

Done.

+    // Dest (or a latter use of all the sources.)
+    Context.insert(InstFakeDef::create(Func, Dest));
     if (auto *Value64 = llvm::dyn_cast<Variable64On32>(Value)) {
       Context.insert(InstFakeUse::create(Func, Value64->getLo()));
       Context.insert(InstFakeUse::create(Func, Value64->getHi()));
     }
-    Context.insert(InstARM32Strex::create(Func, Dest, Value, Addr, Pred));
+    auto *Instr = InstARM32Strex::create(Func, Dest, Value, Addr, Pred);
+    Context.insert(Instr);
+    Instr->setDestRedefined();

[Jim Stichnoth, 2015/10/05 22:07:06]

What do you think about adding Dest as another Src for the InstARM32Strex
instruction?  That would allow you not to have to call setDestRedefined() here. 
The fewer of those calls the better.

[John, 2015/10/06 12:03:38]

Well, if the method was still named nonkillable, sure, I'd do it. Now that it is
named redefined it precisely tells what's happening here. I'd rather leave this
as is. Besides, I don't want to "leak" liveness requirements down to the InstARM
layer.

   }
   void _sub(Variable *Dest, Variable *Src0, Operand *Src1,
             CondARM32::Cond Pred = CondARM32::AL) {