Lower stpcpy_chk when possible.

llvm-svn: 98274

3 files changed, 40 insertions, 6 deletions

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
index c62155ed02d..43ff58d8ff1 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -838,6 +838,19 @@ Instruction *InstCombiner::tryOptimizeCall(CallInst *CI, const TargetData *TD) {
 
   // Should be similar to strcpy.
   if (Name == "__stpcpy_chk") {
+    ConstantInt *SizeCI = dyn_cast<ConstantInt>(CI->getOperand(3));
+    if (!SizeCI)
+      return 0;
+    // If a) we don't have any length information, or b) we know this will
+    // fit then just lower to a plain stpcpy. Otherwise we'll keep our
+    // stpcpy_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 (SizeCI->isAllOnesValue() ||
+        SizeCI->getZExtValue() >= GetStringLength(CI->getOperand(2))) {
+      Value *Ret = EmitStpCpy(CI->getOperand(1), CI->getOperand(2), B, TD);
+      return ReplaceInstUsesWith(*CI, Ret);
+    }
     return 0;
   }
 
diff --git a/llvm/lib/Transforms/Scalar/CodeGenPrepare.cpp b/llvm/lib/Transforms/Scalar/CodeGenPrepare.cpp
index f5ccebfdefa..c428d2b0b0c 100644
--- a/llvm/lib/Transforms/Scalar/CodeGenPrepare.cpp
+++ b/llvm/lib/Transforms/Scalar/CodeGenPrepare.cpp
@@ -624,11 +624,6 @@ bool CodeGenPrepare::OptimizeCallInst(CallInst *CI) {
     ConstantInt *SizeCI = dyn_cast<ConstantInt>(CI->getOperand(3));
     if (!SizeCI)
       return 0;
-    // If a) we don't have any length information, or b) we know this will
-    // fit then just lower to a plain strcpy. Otherwise we'll keep our
-    // strcpy_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 (SizeCI->isAllOnesValue()) {
       Value *Ret = EmitStrCpy(CI->getOperand(1), CI->getOperand(2), B, TD);
       CI->replaceAllUsesWith(Ret);
@@ -638,8 +633,16 @@ bool CodeGenPrepare::OptimizeCallInst(CallInst *CI) {
     return 0;
   }
 
-  // Should be similar to strcpy.
   if (Name == "__stpcpy_chk") {
+    ConstantInt *SizeCI = dyn_cast<ConstantInt>(CI->getOperand(3));
+    if (!SizeCI)
+      return 0;
+    if (SizeCI->isAllOnesValue()) {
+      Value *Ret = EmitStpCpy(CI->getOperand(1), CI->getOperand(2), B, TD);
+      CI->replaceAllUsesWith(Ret);
+      CI->eraseFromParent();
+      return true;
+    }
     return 0;
   }
 
diff --git a/llvm/lib/Transforms/Utils/BuildLibCalls.cpp b/llvm/lib/Transforms/Utils/BuildLibCalls.cpp
index 633aaf4cf8a..7f62166f2e2 100644
--- a/llvm/lib/Transforms/Utils/BuildLibCalls.cpp
+++ b/llvm/lib/Transforms/Utils/BuildLibCalls.cpp
@@ -87,6 +87,24 @@ Value *llvm::EmitStrCpy(Value *Dst, Value *Src, IRBuilder<> &B,
   return CI;
 }
 
+/// EmitStpCpy - Emit a call to the stpcpy function to the builder, for the
+/// specified pointer arguments.
+Value *llvm::EmitStpCpy(Value *Dst, Value *Src, IRBuilder<> &B,
+                        const TargetData *TD) {
+  Module *M = B.GetInsertBlock()->getParent()->getParent();
+  AttributeWithIndex AWI[2];
+  AWI[0] = AttributeWithIndex::get(2, Attribute::NoCapture);
+  AWI[1] = AttributeWithIndex::get(~0u, Attribute::NoUnwind);
+  const Type *I8Ptr = B.getInt8PtrTy();
+  Value *StpCpy = M->getOrInsertFunction("stpcpy", AttrListPtr::get(AWI, 2),
+                                         I8Ptr, I8Ptr, I8Ptr, NULL);
+  CallInst *CI = B.CreateCall2(StpCpy, CastToCStr(Dst, B), CastToCStr(Src, B),
+                               "stpcpy");
+  if (const Function *F = dyn_cast<Function>(StpCpy->stripPointerCasts()))
+    CI->setCallingConv(F->getCallingConv());
+  return CI;
+}
+
 /// EmitStrNCpy - Emit a call to the strncpy function to the builder, for the
 /// specified pointer arguments.
 Value *llvm::EmitStrNCpy(Value *Dst, Value *Src, Value *Len,