Updated the IR converter for the target to eliminate

spurious guard variables on expression statics.

Updated the AST result synthesizer to eliminate the
unneeded result pointer.

Very rudimentary expressions now evaluate correctly
in the target using the new JIT-based mechanism.

llvm-svn: 109317

1 files changed, 82 insertions, 0 deletions

diff --git a/lldb/source/Expression/IRForTarget.cpp b/lldb/source/Expression/IRForTarget.cpp
index 31f3343d82e..e201117338b 100644
--- a/lldb/source/Expression/IRForTarget.cpp
+++ b/lldb/source/Expression/IRForTarget.cpp
@@ -162,6 +162,85 @@ PrintValue(llvm::Value *V, bool truncate = false)
     return s;
 }
 
+static bool isGuardVariableRef(llvm::Value *V)
+{
+    ConstantExpr *C = dyn_cast<ConstantExpr>(V);
+    
+    if (!C || C->getOpcode() != Instruction::BitCast)
+        return false;
+    
+    GlobalVariable *GV = dyn_cast<GlobalVariable>(C->getOperand(0));
+    
+    if (!GV || !GV->hasName() || !GV->getName().startswith("_ZGV"))
+        return false;
+    
+    return true;
+}
+
+static void TurnGuardLoadIntoZero(Instruction* guard_load, Module &M)
+{
+    Constant* zero(ConstantInt::get(Type::getInt8Ty(M.getContext()), 0, true));
+
+    Value::use_iterator ui;
+    
+    for (ui = guard_load->use_begin();
+         ui != guard_load->use_end();
+         ++ui)
+        ui->replaceUsesOfWith(guard_load, zero);
+    
+    guard_load->eraseFromParent();
+}
+
+static void ExciseGuardStore(Instruction* guard_store)
+{
+    guard_store->eraseFromParent();
+}
+
+bool
+IRForTarget::removeGuards(Module &M, BasicBlock &BB)
+{        
+    ///////////////////////////////////////////////////////
+    // Eliminate any reference to guard variables found.
+    //
+    
+    llvm::BasicBlock::iterator ii;
+    
+    typedef llvm::SmallVector <Instruction*, 2> InstrList;
+    typedef InstrList::iterator InstrIterator;
+    
+    InstrList guard_loads;
+    InstrList guard_stores;
+    
+    for (ii = BB.begin();
+         ii != BB.end();
+         ++ii)
+    {
+        Instruction &inst = *ii;
+        
+        if (LoadInst *load = dyn_cast<LoadInst>(&inst))
+            if (isGuardVariableRef(load->getPointerOperand()))
+                guard_loads.push_back(&inst);                
+        
+        if (StoreInst *store = dyn_cast<StoreInst>(&inst))            
+            if (isGuardVariableRef(store->getPointerOperand()))
+                guard_stores.push_back(&inst);
+    }
+    
+    InstrIterator iter;
+    
+    for (iter = guard_loads.begin();
+         iter != guard_loads.end();
+         ++iter)
+        TurnGuardLoadIntoZero(*iter, M);
+    
+    for (iter = guard_stores.begin();
+         iter != guard_stores.end();
+         ++iter)
+        ExciseGuardStore(*iter);
+    
+    return true;
+}
+
 // UnfoldConstant operates on a constant [C] which has just been replaced with a value
 // [new_value].  We assume that new_value has been properly placed early in the function,
 // most likely somewhere in front of the first instruction in the entry basic block 
@@ -363,6 +442,9 @@ IRForTarget::runOnModule(Module &M)
     {
         if (!runOnBasicBlock(M, *bbi))
             return false;
+        
+        if (!removeGuards(M, *bbi))
+            return false;
     }
     
     if (!replaceVariables(M, function))