1 files changed, 72 insertions, 0 deletions

diff --git a/lib/Transforms/Utils/SimplifyLibCalls.cpp b/lib/Transforms/Utils/SimplifyLibCalls.cpp
index a060c3475e..15b3e66f94 100644
--- a/lib/Transforms/Utils/SimplifyLibCalls.cpp
+++ b/lib/Transforms/Utils/SimplifyLibCalls.cpp
@@ -27,11 +27,16 @@
 #include "llvm/IR/LLVMContext.h"
 #include "llvm/IR/Module.h"
 #include "llvm/Support/Allocator.h"
+#include "llvm/Support/CommandLine.h"
 #include "llvm/Target/TargetLibraryInfo.h"
 #include "llvm/Transforms/Utils/BuildLibCalls.h"
 
 using namespace llvm;
 
+static cl::opt<bool>
+ColdErrorCalls("error-reporting-is-cold",  cl::init(true),
+  cl::Hidden, cl::desc("Treat error-reporting calls as cold"));
+
 /// This class is the abstract base class for the set of optimizations that
 /// corresponds to one library call.
 namespace {
@@ -1506,6 +1511,54 @@ struct ToAsciiOpt : public LibCallOptimization {
 // Formatting and IO Library Call Optimizations
 //===----------------------------------------------------------------------===//
 
+struct ErrorReportingOpt : public LibCallOptimization {
+  ErrorReportingOpt(int S = -1) : StreamArg(S) {}
+
+  virtual Value *callOptimizer(Function *Callee, CallInst *CI, IRBuilder<> &) {
+    // Error reporting calls should be cold, mark them as such.
+    // This applies even to non-builtin calls: it is only a hint and applies to
+    // functions that the frontend might not understand as builtins.
+
+    // This heuristic was suggested in:
+    // Improving Static Branch Prediction in a Compiler
+    // Brian L. Deitrich, Ben-Chung Cheng, Wen-mei W. Hwu
+    // Proceedings of PACT'98, Oct. 1998, IEEE
+
+    if (!CI->hasFnAttr(Attribute::Cold) && isReportingError(Callee, CI)) {
+      CI->addAttribute(AttributeSet::FunctionIndex, Attribute::Cold);
+    }
+
+    return 0;
+  }
+
+protected:
+  bool isReportingError(Function *Callee, CallInst *CI) {
+    if (!ColdErrorCalls)
+      return false;
+ 
+    if (!Callee || !Callee->isDeclaration())
+      return false;
+
+    if (StreamArg < 0)
+      return true;
+
+    // These functions might be considered cold, but only if their stream
+    // argument is stderr.
+
+    if (StreamArg >= (int) CI->getNumArgOperands())
+      return false;
+    LoadInst *LI = dyn_cast<LoadInst>(CI->getArgOperand(StreamArg));
+    if (!LI)
+      return false;
+    GlobalVariable *GV = dyn_cast<GlobalVariable>(LI->getPointerOperand());
+    if (!GV || !GV->isDeclaration())
+      return false;
+    return GV->getName() == "stderr";
+  }
+
+  int StreamArg;
+};
+
 struct PrintFOpt : public LibCallOptimization {
   Value *optimizeFixedFormatString(Function *Callee, CallInst *CI,
                                    IRBuilder<> &B) {
@@ -1686,6 +1739,9 @@ struct SPrintFOpt : public LibCallOptimization {
 struct FPrintFOpt : public LibCallOptimization {
   Value *optimizeFixedFormatString(Function *Callee, CallInst *CI,
                                    IRBuilder<> &B) {
+    ErrorReportingOpt ER(/* StreamArg = */ 0);
+    (void) ER.callOptimizer(Callee, CI, B);
+
     // All the optimizations depend on the format string.
     StringRef FormatStr;
     if (!getConstantStringInfo(CI->getArgOperand(1), FormatStr))
@@ -1763,6 +1819,9 @@ struct FPrintFOpt : public LibCallOptimization {
 
 struct FWriteOpt : public LibCallOptimization {
   virtual Value *callOptimizer(Function *Callee, CallInst *CI, IRBuilder<> &B) {
+    ErrorReportingOpt ER(/* StreamArg = */ 3);
+    (void) ER.callOptimizer(Callee, CI, B);
+
     // Require a pointer, an integer, an integer, a pointer, returning integer.
     FunctionType *FT = Callee->getFunctionType();
     if (FT->getNumParams() != 4 || !FT->getParamType(0)->isPointerTy() ||
@@ -1796,6 +1855,9 @@ struct FWriteOpt : public LibCallOptimization {
 
 struct FPutsOpt : public LibCallOptimization {
   virtual Value *callOptimizer(Function *Callee, CallInst *CI, IRBuilder<> &B) {
+    ErrorReportingOpt ER(/* StreamArg = */ 1);
+    (void) ER.callOptimizer(Callee, CI, B);
+
     // These optimizations require DataLayout.
     if (!TD) return 0;
 
@@ -1924,6 +1986,9 @@ static IsAsciiOpt IsAscii;
 static ToAsciiOpt ToAscii;
 
 // Formatting and IO library call optimizations.
+static ErrorReportingOpt ErrorReporting;
+static ErrorReportingOpt ErrorReporting0(0);
+static ErrorReportingOpt ErrorReporting1(1);
 static PrintFOpt PrintF;
 static SPrintFOpt SPrintF;
 static FPrintFOpt FPrintF;
@@ -2038,6 +2103,13 @@ LibCallOptimization *LibCallSimplifierImpl::lookupOptimization(CallInst *CI) {
         return &FPuts;
       case LibFunc::puts:
         return &Puts;
+      case LibFunc::perror:
+        return &ErrorReporting;
+      case LibFunc::vfprintf:
+      case LibFunc::fiprintf:
+        return &ErrorReporting0;
+      case LibFunc::fputc:
+        return &ErrorReporting1;
       case LibFunc::ceil:
       case LibFunc::fabs:
       case LibFunc::floor: