instcombine: Migrate strcpy optimizations

This patch migrates the strcpy optimizations from the simplify-libcalls pass
into the instcombine library call simplifier.  Note also that StrCpyChkOpt
has been updated with a few simplifications that were being done in the
simplify-libcalls version of StrCpyOpt, but not in the migrated implementation
of StrCpyOpt.  There is no reason to overload StrCpyOpt with fortified and
regular simplifications in the new model since there is already a dedicated
simplifier for __strcpy_chk.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@166198 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 49 insertions, 2 deletions

diff --git a/lib/Transforms/Utils/SimplifyLibCalls.cpp b/lib/Transforms/Utils/SimplifyLibCalls.cpp
index bd28ec3..032a2fd 100644
--- a/lib/Transforms/Utils/SimplifyLibCalls.cpp
+++ b/lib/Transforms/Utils/SimplifyLibCalls.cpp
@@ -183,14 +183,30 @@ struct StrCpyChkOpt : public InstFortifiedLibCallOptimization {
         FT->getParamType(2) != TD->getIntPtrType(Context))
       return 0;
 
+    Value *Dst = CI->getArgOperand(0), *Src = CI->getArgOperand(1);
+    if (Dst == Src)      // __strcpy_chk(x,x)  -> x
+      return Src;
+
     // If a) we don't have any length information, or b) we know this will
     // fit then just lower to a plain st[rp]cpy. Otherwise we'll keep our
     // st[rp]cpy_chk call which may fail at runtime if the size is too long.
     // TODO: It might be nice to get a maximum length out of the possible
     // string lengths for varying.
     if (isFoldable(2, 1, true)) {
-      Value *Ret = EmitStrCpy(CI->getArgOperand(0), CI->getArgOperand(1), B, TD,
-                              TLI, Name.substr(2, 6));
+      Value *Ret = EmitStrCpy(Dst, Src, B, TD, TLI, Name.substr(2, 6));
+      return Ret;
+    } else {
+      // Maybe we can stil fold __strcpy_chk to __memcpy_chk.
+      uint64_t Len = GetStringLength(Src);
+      if (Len == 0) return 0;
+
+      // This optimization require DataLayout.
+      if (!TD) return 0;
+
+      Value *Ret =
+	EmitMemCpyChk(Dst, Src,
+                      ConstantInt::get(TD->getIntPtrType(Context), Len),
+                      CI->getArgOperand(2), B, TD, TLI);
       return Ret;
     }
     return 0;
@@ -497,6 +513,35 @@ struct StrNCmpOpt : public LibCallOptimization {
   }
 };
 
+struct StrCpyOpt : public LibCallOptimization {
+  virtual Value *callOptimizer(Function *Callee, CallInst *CI, IRBuilder<> &B) {
+    // Verify the "strcpy" function prototype.
+    FunctionType *FT = Callee->getFunctionType();
+    if (FT->getNumParams() != 2 ||
+        FT->getReturnType() != FT->getParamType(0) ||
+        FT->getParamType(0) != FT->getParamType(1) ||
+        FT->getParamType(0) != B.getInt8PtrTy())
+      return 0;
+
+    Value *Dst = CI->getArgOperand(0), *Src = CI->getArgOperand(1);
+    if (Dst == Src)      // strcpy(x,x)  -> x
+      return Src;
+
+    // These optimizations require DataLayout.
+    if (!TD) return 0;
+
+    // See if we can get the length of the input string.
+    uint64_t Len = GetStringLength(Src);
+    if (Len == 0) return 0;
+
+    // We have enough information to now generate the memcpy call to do the
+    // copy for us.  Make a memcpy to copy the nul byte with align = 1.
+    B.CreateMemCpy(Dst, Src,
+		   ConstantInt::get(TD->getIntPtrType(*Context), Len), 1);
+    return Dst;
+  }
+};
+
 } // End anonymous namespace.
 
 namespace llvm {
@@ -520,6 +565,7 @@ class LibCallSimplifierImpl {
   StrRChrOpt StrRChr;
   StrCmpOpt StrCmp;
   StrNCmpOpt StrNCmp;
+  StrCpyOpt StrCpy;
 
   void initOptimizations();
 public:
@@ -548,6 +594,7 @@ void LibCallSimplifierImpl::initOptimizations() {
   Optimizations["strncat"] = &StrNCat;
   Optimizations["strchr"] = &StrChr;
   Optimizations["strrchr"] = &StrRChr;
+  Optimizations["strcpy"] = &StrCpy;
 }
 
 Value *LibCallSimplifierImpl::optimizeCall(CallInst *CI) {