instcombine: Migrate printf optimizations

This patch migrates the printf optimizations from the simplify-libcalls
pass into the instcombine library call simplifier.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@168604 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Transforms/Utils/SimplifyLibCalls.cpp

@@ -102,6 +102,15 @@ static bool isOnlyUsedInEqualityComparison(Value *V, Value *With) {
   return true;
 }
 
+static bool callHasFloatingPointArgument(const CallInst *CI) {
+  for (CallInst::const_op_iterator it = CI->op_begin(), e = CI->op_end();
+       it != e; ++it) {
+    if ((*it)->getType()->isFloatingPointTy())
+      return true;
+  }
+  return false;
+}
+
 //===----------------------------------------------------------------------===//
 // Fortified Library Call Optimizations
 //===----------------------------------------------------------------------===//
@@ -1312,6 +1321,94 @@ struct ToAsciiOpt : public LibCallOptimization {
   }
 };
 
+//===----------------------------------------------------------------------===//
+// Formatting and IO Library Call Optimizations
+//===----------------------------------------------------------------------===//
+
+struct PrintFOpt : public LibCallOptimization {
+  Value *optimizeFixedFormatString(Function *Callee, CallInst *CI,
+                                   IRBuilder<> &B) {
+    // Check for a fixed format string.
+    StringRef FormatStr;
+    if (!getConstantStringInfo(CI->getArgOperand(0), FormatStr))
+      return 0;
+
+    // Empty format string -> noop.
+    if (FormatStr.empty())  // Tolerate printf's declared void.
+      return CI->use_empty() ? (Value*)CI :
+                               ConstantInt::get(CI->getType(), 0);
+
+    // Do not do any of the following transformations if the printf return value
+    // is used, in general the printf return value is not compatible with either
+    // putchar() or puts().
+    if (!CI->use_empty())
+      return 0;
+
+    // printf("x") -> putchar('x'), even for '%'.
+    if (FormatStr.size() == 1) {
+      Value *Res = EmitPutChar(B.getInt32(FormatStr[0]), B, TD, TLI);
+      if (CI->use_empty() || !Res) return Res;
+      return B.CreateIntCast(Res, CI->getType(), true);
+    }
+
+    // printf("foo\n") --> puts("foo")
+    if (FormatStr[FormatStr.size()-1] == '\n' &&
+        FormatStr.find('%') == std::string::npos) {  // no format characters.
+      // Create a string literal with no \n on it.  We expect the constant merge
+      // pass to be run after this pass, to merge duplicate strings.
+      FormatStr = FormatStr.drop_back();
+      Value *GV = B.CreateGlobalString(FormatStr, "str");
+      Value *NewCI = EmitPutS(GV, B, TD, TLI);
+      return (CI->use_empty() || !NewCI) ?
+              NewCI :
+              ConstantInt::get(CI->getType(), FormatStr.size()+1);
+    }
+
+    // Optimize specific format strings.
+    // printf("%c", chr) --> putchar(chr)
+    if (FormatStr == "%c" && CI->getNumArgOperands() > 1 &&
+        CI->getArgOperand(1)->getType()->isIntegerTy()) {
+      Value *Res = EmitPutChar(CI->getArgOperand(1), B, TD, TLI);
+
+      if (CI->use_empty() || !Res) return Res;
+      return B.CreateIntCast(Res, CI->getType(), true);
+    }
+
+    // printf("%s\n", str) --> puts(str)
+    if (FormatStr == "%s\n" && CI->getNumArgOperands() > 1 &&
+        CI->getArgOperand(1)->getType()->isPointerTy()) {
+      return EmitPutS(CI->getArgOperand(1), B, TD, TLI);
+    }
+    return 0;
+  }
+
+  virtual Value *callOptimizer(Function *Callee, CallInst *CI, IRBuilder<> &B) {
+    // Require one fixed pointer argument and an integer/void result.
+    FunctionType *FT = Callee->getFunctionType();
+    if (FT->getNumParams() < 1 || !FT->getParamType(0)->isPointerTy() ||
+        !(FT->getReturnType()->isIntegerTy() ||
+          FT->getReturnType()->isVoidTy()))
+      return 0;
+
+    if (Value *V = optimizeFixedFormatString(Callee, CI, B)) {
+      return V;
+    }
+
+    // printf(format, ...) -> iprintf(format, ...) if no floating point
+    // arguments.
+    if (TLI->has(LibFunc::iprintf) && !callHasFloatingPointArgument(CI)) {
+      Module *M = B.GetInsertBlock()->getParent()->getParent();
+      Constant *IPrintFFn =
+        M->getOrInsertFunction("iprintf", FT, Callee->getAttributes());
+      CallInst *New = cast<CallInst>(CI->clone());
+      New->setCalledFunction(IPrintFFn);
+      B.Insert(New);
+      return New;
+    }
+    return 0;
+  }
+};
+
 } // End anonymous namespace.
 
 namespace llvm {
@@ -1365,6 +1462,9 @@ class LibCallSimplifierImpl {
   IsAsciiOpt IsAscii;
   ToAsciiOpt ToAscii;
 
+  // Formatting and IO library call optimizations.
+  PrintFOpt PrintF;
+
   void initOptimizations();
   void addOpt(LibFunc::Func F, LibCallOptimization* Opt);
   void addOpt(LibFunc::Func F1, LibFunc::Func F2, LibCallOptimization* Opt);
@@ -1485,6 +1585,9 @@ void LibCallSimplifierImpl::initOptimizations() {
   addOpt(LibFunc::isdigit, &IsDigit);
   addOpt(LibFunc::isascii, &IsAscii);
   addOpt(LibFunc::toascii, &ToAscii);
+
+  // Formatting and IO library call optimizations.
+  addOpt(LibFunc::printf, &PrintF);
 }
 
 Value *LibCallSimplifierImpl::optimizeCall(CallInst *CI) {