1 files changed, 99 insertions, 0 deletions

diff --git a/lib/Transforms/Utils/SimplifyLibCalls.cpp b/lib/Transforms/Utils/SimplifyLibCalls.cpp
index 5ce5843b21..bd28ec3527 100644
--- a/lib/Transforms/Utils/SimplifyLibCalls.cpp
+++ b/lib/Transforms/Utils/SimplifyLibCalls.cpp
@@ -402,6 +402,101 @@ struct StrRChrOpt : public LibCallOptimization {
   }
 };
 
+struct StrCmpOpt : public LibCallOptimization {
+  virtual Value *callOptimizer(Function *Callee, CallInst *CI, IRBuilder<> &B) {
+    // Verify the "strcmp" function prototype.
+    FunctionType *FT = Callee->getFunctionType();
+    if (FT->getNumParams() != 2 ||
+        !FT->getReturnType()->isIntegerTy(32) ||
+        FT->getParamType(0) != FT->getParamType(1) ||
+        FT->getParamType(0) != B.getInt8PtrTy())
+      return 0;
+
+    Value *Str1P = CI->getArgOperand(0), *Str2P = CI->getArgOperand(1);
+    if (Str1P == Str2P)      // strcmp(x,x)  -> 0
+      return ConstantInt::get(CI->getType(), 0);
+
+    StringRef Str1, Str2;
+    bool HasStr1 = getConstantStringInfo(Str1P, Str1);
+    bool HasStr2 = getConstantStringInfo(Str2P, Str2);
+
+    // strcmp(x, y)  -> cnst  (if both x and y are constant strings)
+    if (HasStr1 && HasStr2)
+      return ConstantInt::get(CI->getType(), Str1.compare(Str2));
+
+    if (HasStr1 && Str1.empty()) // strcmp("", x) -> -*x
+      return B.CreateNeg(B.CreateZExt(B.CreateLoad(Str2P, "strcmpload"),
+                                      CI->getType()));
+
+    if (HasStr2 && Str2.empty()) // strcmp(x,"") -> *x
+      return B.CreateZExt(B.CreateLoad(Str1P, "strcmpload"), CI->getType());
+
+    // strcmp(P, "x") -> memcmp(P, "x", 2)
+    uint64_t Len1 = GetStringLength(Str1P);
+    uint64_t Len2 = GetStringLength(Str2P);
+    if (Len1 && Len2) {
+      // These optimizations require DataLayout.
+      if (!TD) return 0;
+
+      return EmitMemCmp(Str1P, Str2P,
+                        ConstantInt::get(TD->getIntPtrType(*Context),
+                        std::min(Len1, Len2)), B, TD, TLI);
+    }
+
+    return 0;
+  }
+};
+
+struct StrNCmpOpt : public LibCallOptimization {
+  virtual Value *callOptimizer(Function *Callee, CallInst *CI, IRBuilder<> &B) {
+    // Verify the "strncmp" function prototype.
+    FunctionType *FT = Callee->getFunctionType();
+    if (FT->getNumParams() != 3 ||
+        !FT->getReturnType()->isIntegerTy(32) ||
+        FT->getParamType(0) != FT->getParamType(1) ||
+        FT->getParamType(0) != B.getInt8PtrTy() ||
+        !FT->getParamType(2)->isIntegerTy())
+      return 0;
+
+    Value *Str1P = CI->getArgOperand(0), *Str2P = CI->getArgOperand(1);
+    if (Str1P == Str2P)      // strncmp(x,x,n)  -> 0
+      return ConstantInt::get(CI->getType(), 0);
+
+    // Get the length argument if it is constant.
+    uint64_t Length;
+    if (ConstantInt *LengthArg = dyn_cast<ConstantInt>(CI->getArgOperand(2)))
+      Length = LengthArg->getZExtValue();
+    else
+      return 0;
+
+    if (Length == 0) // strncmp(x,y,0)   -> 0
+      return ConstantInt::get(CI->getType(), 0);
+
+    if (TD && Length == 1) // strncmp(x,y,1) -> memcmp(x,y,1)
+      return EmitMemCmp(Str1P, Str2P, CI->getArgOperand(2), B, TD, TLI);
+
+    StringRef Str1, Str2;
+    bool HasStr1 = getConstantStringInfo(Str1P, Str1);
+    bool HasStr2 = getConstantStringInfo(Str2P, Str2);
+
+    // strncmp(x, y)  -> cnst  (if both x and y are constant strings)
+    if (HasStr1 && HasStr2) {
+      StringRef SubStr1 = Str1.substr(0, Length);
+      StringRef SubStr2 = Str2.substr(0, Length);
+      return ConstantInt::get(CI->getType(), SubStr1.compare(SubStr2));
+    }
+
+    if (HasStr1 && Str1.empty())  // strncmp("", x, n) -> -*x
+      return B.CreateNeg(B.CreateZExt(B.CreateLoad(Str2P, "strcmpload"),
+                                      CI->getType()));
+
+    if (HasStr2 && Str2.empty())  // strncmp(x, "", n) -> *x
+      return B.CreateZExt(B.CreateLoad(Str1P, "strcmpload"), CI->getType());
+
+    return 0;
+  }
+};
+
 } // End anonymous namespace.
 
 namespace llvm {
@@ -423,6 +518,8 @@ class LibCallSimplifierImpl {
   StrNCatOpt StrNCat;
   StrChrOpt StrChr;
   StrRChrOpt StrRChr;
+  StrCmpOpt StrCmp;
+  StrNCmpOpt StrNCmp;
 
   void initOptimizations();
 public:
@@ -443,6 +540,8 @@ void LibCallSimplifierImpl::initOptimizations() {
   Optimizations["__stpcpy_chk"] = &StrCpyChk;
   Optimizations["__strncpy_chk"] = &StrNCpyChk;
   Optimizations["__stpncpy_chk"] = &StrNCpyChk;
+  Optimizations["strcmp"] = &StrCmp;
+  Optimizations["strncmp"] = &StrNCmp;
 
   // String and memory library call optimizations.
   Optimizations["strcat"] = &StrCat;