From 35b9b49fd17fe8600d5a6ac25d812694af7b1051 Mon Sep 17 00:00:00 2001
From: Chris Lattner <sabre@nondot.org>
Date: Sat, 14 Apr 2007 01:17:48 +0000
Subject: [PATCH] Implement a few missing xforms: printf("foo\n") -> puts. 
 printf("x") -> putchar printf("") -> noop.  Still need to do the xforms for
 fprintf.

This implements Transforms/SimplifyLibCalls/Printf.ll


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@35984 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Transforms/IPO/SimplifyLibCalls.cpp | 57 +++++++++++++++++++++----
 1 file changed, 48 insertions(+), 9 deletions(-)

diff --git a/lib/Transforms/IPO/SimplifyLibCalls.cpp b/lib/Transforms/IPO/SimplifyLibCalls.cpp
index 87c1480fba7..b7b5bee1eb2 100644
--- a/lib/Transforms/IPO/SimplifyLibCalls.cpp
+++ b/lib/Transforms/IPO/SimplifyLibCalls.cpp
@@ -1154,22 +1154,61 @@ public:
 
   /// @brief Make sure that the "printf" function has the right prototype
   virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
-    // Just make sure this has at least 1 arguments
-    return F->arg_size() >= 1;
+    // Just make sure this has at least 1 argument and returns an integer or
+    // void type.
+    const FunctionType *FT = F->getFunctionType();
+    return FT->getNumParams() >= 1 &&
+          (isa<IntegerType>(FT->getReturnType()) ||
+           FT->getReturnType() == Type::VoidTy);
   }
 
   /// @brief Perform the printf optimization.
   virtual bool OptimizeCall(CallInst *CI, SimplifyLibCalls &SLC) {
-    // If the call has more than 2 operands, we can't optimize it
-    if (CI->getNumOperands() != 3)
-      return false;
-
     // All the optimizations depend on the length of the first argument and the
     // fact that it is a constant string array. Check that now
     std::string FormatStr;
     if (!GetConstantStringInfo(CI->getOperand(1), FormatStr))
       return false;
+    
+    // If this is a simple constant string with no format specifiers that ends
+    // with a \n, turn it into a puts call.
+    if (FormatStr.empty()) {
+      // Tolerate printf's declared void.
+      if (CI->use_empty()) return ReplaceCallWith(CI, 0);
+      return ReplaceCallWith(CI, ConstantInt::get(CI->getType(), 0));
+    }
+    
+    if (FormatStr.size() == 1) {
+      // Turn this into a putchar call, even if it is a %.
+      Value *V = ConstantInt::get(Type::Int32Ty, FormatStr[0]);
+      new CallInst(SLC.get_putchar(), V, "", CI);
+      if (CI->use_empty()) return ReplaceCallWith(CI, 0);
+      return ReplaceCallWith(CI, ConstantInt::get(CI->getType(), 1));
+    }
 
+    // Check to see if the format str is something like "foo\n", in which case
+    // we convert it to a puts call.  We don't allow it to contain any format
+    // characters.
+    if (FormatStr[FormatStr.size()-1] == '\n' &&
+        FormatStr.find('%') == std::string::npos) {
+      // 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.erase(FormatStr.end()-1);
+      Constant *Init = ConstantArray::get(FormatStr, true);
+      Constant *GV = new GlobalVariable(Init->getType(), true,
+                                        GlobalVariable::InternalLinkage,
+                                        Init, "str",
+                                     CI->getParent()->getParent()->getParent());
+      // Cast GV to be a pointer to char.
+      GV = ConstantExpr::getBitCast(GV, PointerType::get(Type::Int8Ty));
+      new CallInst(SLC.get_puts(), GV, "", CI);
+
+      if (CI->use_empty()) return ReplaceCallWith(CI, 0);
+      return ReplaceCallWith(CI,
+                             ConstantInt::get(CI->getType(), FormatStr.size()));
+    }
+    
+    
     // Only support %c or "%s\n" for now.
     if (FormatStr.size() < 2 || FormatStr[0] != '%')
       return false;
@@ -1178,7 +1217,7 @@ public:
     switch (FormatStr[1]) {
     default:  return false;
     case 's':
-      if (FormatStr != "%s\n" ||
+      if (FormatStr != "%s\n" || CI->getNumOperands() < 3 ||
           // TODO: could insert strlen call to compute string length.
           !CI->use_empty())
         return false;
@@ -1189,7 +1228,7 @@ public:
       return ReplaceCallWith(CI, 0);
     case 'c': {
       // printf("%c",c) -> putchar(c)
-      if (FormatStr.size() != 2)
+      if (FormatStr.size() != 2 || CI->getNumOperands() < 3)
         return false;
       
       Value *V = CI->getOperand(2);
@@ -1917,7 +1956,7 @@ static Value *CastToCStr(Value *V, Instruction *IP) {
 //   * pow(pow(x,y),z)-> pow(x,y*z)
 //
 // puts:
-//   * puts("") -> fputc("\n",stdout) (how do we get "stdout"?)
+//   * puts("") -> putchar("\n")
 //
 // round, roundf, roundl:
 //   * round(cnst) -> cnst'
-- 
2.34.1