1 files changed, 82 insertions, 38 deletions

diff --git a/lib/Analysis/ValueTracking.cpp b/lib/Analysis/ValueTracking.cpp
index 20fa69ea24..d3a7d1bfeb 100644
--- a/lib/Analysis/ValueTracking.cpp
+++ b/lib/Analysis/ValueTracking.cpp
@@ -17,9 +17,10 @@
 #include "llvm/Instructions.h"
 #include "llvm/GlobalVariable.h"
 #include "llvm/IntrinsicInst.h"
-#include "llvm/Target/TargetData.h"
+#include "llvm/ADT/DenseMap.h"
 #include "llvm/Support/GetElementPtrTypeIterator.h"
 #include "llvm/Support/MathExtras.h"
+#include "llvm/Target/TargetData.h"
 #include <cstring>
 using namespace llvm;
 
@@ -928,6 +929,7 @@ Value *llvm::FindInsertedValue(Value *V, const unsigned *idx_begin,
     return FindInsertedValue(I->getAggregateOperand(), Idxs.begin(), Idxs.end(),
                              InsertBefore);
   }
+
   // Otherwise, we don't know (such as, extracting from a function return value
   // or load instruction)
   return 0;
@@ -936,55 +938,86 @@ Value *llvm::FindInsertedValue(Value *V, const unsigned *idx_begin,
 /// GetConstantStringInfo - This function computes the length of a
 /// null-terminated C string pointed to by V.  If successful, it returns true
 /// and returns the string in Str.  If unsuccessful, it returns false.
-bool llvm::GetConstantStringInfo(Value *V, std::string &Str, uint64_t Offset,
-                                 bool StopAtNul) {
-  // If V is NULL then return false;
-  if (V == NULL) return false;
+const char *llvm::GetConstantStringInfo(Value *V, uint64_t Offset,
+                                        bool StopAtNul) {
+  static DenseMap<Value*, std::string> StringInfoMap;
+  static DenseMap<Value*, bool> NulMap;
+
+  // If we've already determined that the Value is NUL, then return 0.
+  if (NulMap[V])
+    return 0;
+
+  // Check to see if we've already calculated the string info.
+  if (StringInfoMap.find(V) != StringInfoMap.end())
+    return StringInfoMap.lookup(V).c_str();
+
+  // If V is NULL then return nul.
+  if (V == 0) {
+    NulMap[V] = true;
+    return 0;
+  }
+
+  std::string *Str = &StringInfoMap.FindAndConstruct(V).second;
+  Str->clear();
 
   // Look through bitcast instructions.
   if (BitCastInst *BCI = dyn_cast<BitCastInst>(V))
-    return GetConstantStringInfo(BCI->getOperand(0), Str, Offset, StopAtNul);
-  
+    return GetConstantStringInfo(BCI->getOperand(0), Offset, StopAtNul);
+
   // If the value is not a GEP instruction nor a constant expression with a
   // GEP instruction, then return false because ConstantArray can't occur
   // any other way
   User *GEP = 0;
+
   if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(V)) {
     GEP = GEPI;
   } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
     if (CE->getOpcode() == Instruction::BitCast)
-      return GetConstantStringInfo(CE->getOperand(0), Str, Offset, StopAtNul);
-    if (CE->getOpcode() != Instruction::GetElementPtr)
-      return false;
+      return GetConstantStringInfo(CE->getOperand(0), Offset, StopAtNul);
+
+    if (CE->getOpcode() != Instruction::GetElementPtr) {
+      NulMap[V] = true;
+      return 0;
+    }
+
     GEP = CE;
   }
   
   if (GEP) {
     // Make sure the GEP has exactly three arguments.
-    if (GEP->getNumOperands() != 3)
-      return false;
-    
+    if (GEP->getNumOperands() != 3) {
+      NulMap[V] = true;
+      return 0;
+    }
+
     // Make sure the index-ee is a pointer to array of i8.
     const PointerType *PT = cast<PointerType>(GEP->getOperand(0)->getType());
     const ArrayType *AT = dyn_cast<ArrayType>(PT->getElementType());
-    if (AT == 0 || AT->getElementType() != Type::Int8Ty)
-      return false;
+    if (AT == 0 || AT->getElementType() != Type::Int8Ty) {
+      NulMap[V] = true;
+      return 0;
+    }
     
     // Check to make sure that the first operand of the GEP is an integer and
     // has value 0 so that we are sure we're indexing into the initializer.
     ConstantInt *FirstIdx = dyn_cast<ConstantInt>(GEP->getOperand(1));
-    if (FirstIdx == 0 || !FirstIdx->isZero())
-      return false;
+    if (FirstIdx == 0 || !FirstIdx->isZero()) {
+      NulMap[V] = true;
+      return 0;
+    }
     
     // If the second index isn't a ConstantInt, then this is a variable index
     // into the array.  If this occurs, we can't say anything meaningful about
     // the string.
     uint64_t StartIdx = 0;
-    if (ConstantInt *CI = dyn_cast<ConstantInt>(GEP->getOperand(2)))
+    if (ConstantInt *CI = dyn_cast<ConstantInt>(GEP->getOperand(2))) {
       StartIdx = CI->getZExtValue();
-    else
-      return false;
-    return GetConstantStringInfo(GEP->getOperand(0), Str, StartIdx+Offset,
+    } else {
+      NulMap[V] = true;
+      return 0;
+    }
+
+    return GetConstantStringInfo(GEP->getOperand(0), StartIdx + Offset,
                                  StopAtNul);
   }
   
@@ -992,42 +1025,53 @@ bool llvm::GetConstantStringInfo(Value *V, std::string &Str, uint64_t Offset,
   // variable that is a constant and is initialized. The referenced constant
   // initializer is the array that we'll use for optimization.
   GlobalVariable* GV = dyn_cast<GlobalVariable>(V);
-  if (!GV || !GV->isConstant() || !GV->hasInitializer())
-    return false;
+  if (!GV || !GV->isConstant() || !GV->hasInitializer()) {
+    NulMap[V] = true;
+    return 0;
+  }
   Constant *GlobalInit = GV->getInitializer();
   
   // Handle the ConstantAggregateZero case
-  if (isa<ConstantAggregateZero>(GlobalInit)) {
+  if (isa<ConstantAggregateZero>(GlobalInit))
     // This is a degenerate case. The initializer is constant zero so the
     // length of the string must be zero.
-    Str.clear();
-    return true;
-  }
+    return "";
   
   // Must be a Constant Array
   ConstantArray *Array = dyn_cast<ConstantArray>(GlobalInit);
-  if (Array == 0 || Array->getType()->getElementType() != Type::Int8Ty)
-    return false;
+  if (Array == 0 || Array->getType()->getElementType() != Type::Int8Ty) {
+    NulMap[V] = true;
+    return 0;
+  }
   
   // Get the number of elements in the array
   uint64_t NumElts = Array->getType()->getNumElements();
   
-  if (Offset > NumElts)
-    return false;
+  if (Offset > NumElts) {
+    NulMap[V] = true;
+    return 0;
+  }
   
   // Traverse the constant array from 'Offset' which is the place the GEP refers
   // to in the array.
-  Str.reserve(NumElts-Offset);
+  Str->reserve(NumElts - Offset);
+
   for (unsigned i = Offset; i != NumElts; ++i) {
     Constant *Elt = Array->getOperand(i);
     ConstantInt *CI = dyn_cast<ConstantInt>(Elt);
-    if (!CI) // This array isn't suitable, non-int initializer.
-      return false;
+
+    if (!CI) {                // This array isn't suitable, non-int initializer.
+      StringInfoMap.erase(V);
+      NulMap[V] = true;
+      return 0;
+    }
+
     if (StopAtNul && CI->isZero())
-      return true; // we found end of string, success!
-    Str += (char)CI->getZExtValue();
+      return Str->c_str(); // we found end of string, success!
+
+    Str->operator+=((char)CI->getZExtValue());
   }
-  
+
   // The array isn't null terminated, but maybe this is a memcpy, not a strcpy.
-  return true;
+  return Str->c_str();
 }