4 files changed, 42 insertions, 3 deletions

diff --git a/clang/lib/CodeGen/CGBuiltin.cpp b/clang/lib/CodeGen/CGBuiltin.cpp
index b990c199953..6e59226a6e8 100644
--- a/clang/lib/CodeGen/CGBuiltin.cpp
+++ b/clang/lib/CodeGen/CGBuiltin.cpp
@@ -36,7 +36,8 @@ static RValue EmitBinaryAtomic(CodeGenFunction& CFG,
                                              CFG.EmitScalarExpr(E->getArg(1))));
 }
 
-RValue CodeGenFunction::EmitBuiltinExpr(unsigned BuiltinID, const CallExpr *E) {
+RValue CodeGenFunction::EmitBuiltinExpr(const FunctionDecl *FD, 
+                                        unsigned BuiltinID, const CallExpr *E) {
   // See if we can constant fold this builtin.  If so, don't emit it at all.
   Expr::EvalResult Result;
   if (E->Evaluate(Result, CGM.getContext())) {
@@ -324,6 +325,34 @@ RValue CodeGenFunction::EmitBuiltinExpr(unsigned BuiltinID, const CallExpr *E) {
   }
   case Builtin::BI__sync_lock_test_and_set:
     return EmitBinaryAtomic(*this, Intrinsic::atomic_swap, E);
+
+
+    // Library functions with special handling.
+
+  case Builtin::BIsqrt:
+  case Builtin::BIsqrtf:
+  case Builtin::BIsqrtl: {
+    // Rewrite sqrt to intrinsic if allowed.
+    if (!FD->getAttr<ConstAttr>())
+      break;
+    Value *Arg0 = EmitScalarExpr(E->getArg(0));
+    const llvm::Type *ArgType = Arg0->getType();
+    Value *F = CGM.getIntrinsic(Intrinsic::sqrt, &ArgType, 1);
+    return RValue::get(Builder.CreateCall(F, Arg0, "tmp"));
+  }
+
+  case Builtin::BIpow:
+  case Builtin::BIpowf:
+  case Builtin::BIpowl: {
+    // Rewrite sqrt to intrinsic if allowed.
+    if (!FD->getAttr<ConstAttr>())
+      break;
+    Value *Base = EmitScalarExpr(E->getArg(0));
+    Value *Exponent = EmitScalarExpr(E->getArg(1));
+    const llvm::Type *ArgType = Base->getType();
+    Value *F = CGM.getIntrinsic(Intrinsic::pow, &ArgType, 1);
+    return RValue::get(Builder.CreateCall2(F, Base, Exponent, "tmp"));
+  }
   }
   
   // If this is an alias for a libm function (e.g. __builtin_sin) turn it into
diff --git a/clang/lib/CodeGen/CGExpr.cpp b/clang/lib/CodeGen/CGExpr.cpp
index 4dc8a9e1d4d..b151dd2102c 100644
--- a/clang/lib/CodeGen/CGExpr.cpp
+++ b/clang/lib/CodeGen/CGExpr.cpp
@@ -969,7 +969,7 @@ RValue CodeGenFunction::EmitCallExpr(const CallExpr *E) {
       if (const FunctionDecl *FDecl = 
           dyn_cast<const FunctionDecl>(DRExpr->getDecl()))
         if (unsigned builtinID = FDecl->getBuiltinID(getContext()))
-          return EmitBuiltinExpr(builtinID, E);
+          return EmitBuiltinExpr(FDecl, builtinID, E);
 
   if (E->getCallee()->getType()->isBlockPointerType())
     return EmitBlockCallExpr(E);
diff --git a/clang/lib/CodeGen/CodeGenFunction.h b/clang/lib/CodeGen/CodeGenFunction.h
index 5f42a429e06..7f36c71ab6f 100644
--- a/clang/lib/CodeGen/CodeGenFunction.h
+++ b/clang/lib/CodeGen/CodeGenFunction.h
@@ -631,7 +631,8 @@ public:
                       CallExpr::const_arg_iterator ArgBeg,
                       CallExpr::const_arg_iterator ArgEnd);
 
-  RValue EmitBuiltinExpr(unsigned BuiltinID, const CallExpr *E);
+  RValue EmitBuiltinExpr(const FunctionDecl *FD, 
+                         unsigned BuiltinID, const CallExpr *E);
 
   RValue EmitBlockCallExpr(const CallExpr *E);
   
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 2692cd99db4..4f8b245ef36 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -2956,6 +2956,15 @@ void Sema::AddKnownFunctionAttributes(FunctionDecl *FD) {
       if (!FD->getAttr<FormatAttr>())
         FD->addAttr(new FormatAttr("printf", FormatIdx + 1, FormatIdx + 2));
     }
+
+    // Mark const if we don't care about errno and that is the only
+    // thing preventing the function from being const. This allows
+    // IRgen to use LLVM intrinsics for such functions.
+    if (!getLangOptions().MathErrno &&
+        Context.BuiltinInfo.isConstWithoutErrno(BuiltinID)) {
+      if (!FD->getAttr<ConstAttr>())
+        FD->addAttr(new ConstAttr());
+    }
   }
 
   IdentifierInfo *Name = FD->getIdentifier();