Cleanup this example, simplifying it and making it conform to LLVM coding

standards


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@17459 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 76 insertions, 147 deletions

diff --git a/examples/Fibonacci/fibonacci.cpp b/examples/Fibonacci/fibonacci.cpp
index f34aed762a2..43c73bad599 100644
--- a/examples/Fibonacci/fibonacci.cpp
+++ b/examples/Fibonacci/fibonacci.cpp
@@ -7,182 +7,111 @@
 // 
 //===----------------------------------------------------------------------===//
 //
-// This small program provides an example of how to build quickly a small
-// module with function Fibonacci and execute it with the JIT. 
+// This small program provides an example of how to build quickly a small module
+// with function Fibonacci and execute it with the JIT.
 //
-// This simple example shows as well 30% speed up with LLVM 1.3
-// in comparison to gcc 3.3.3 at AMD Athlon XP 1500+ .
+// The goal of this snippet is to create in the memory the LLVM module
+// consisting of one function as follow:
 //
-// (Modified from HowToUseJIT.cpp and Stacker/lib/compiler/StackerCompiler.cpp)
+//   int fib(int x) {
+//     if(x<=2) return 1;
+//     return fib(x-1)+fib(x-2);
+//   }
 // 
-//===------------------------------------------------------------------------===
-// Goal: 
-//  The goal of this snippet is to create in the memory
-//  the LLVM module consisting of one function as follow:
-//
-// int fib(int x) {
-//   if(x<=2) return 1;
-//   return fib(x-1)+fib(x-2);
-// }
-// 
-// then compile the module via JIT, then execute the `fib' 
+// Once we have this, we compile the module via JIT, then execute the `fib'
 // function and return result to a driver, i.e. to a "host program".
 //
+//===----------------------------------------------------------------------===//
 
-#include <iostream>
-
-#include <llvm/Module.h>
-#include <llvm/DerivedTypes.h>
-#include <llvm/Constants.h>
-#include <llvm/Instructions.h>
-#include <llvm/ModuleProvider.h>
-#include <llvm/Analysis/Verifier.h>
+#include "llvm/Module.h"
+#include "llvm/DerivedTypes.h"
+#include "llvm/Constants.h"
+#include "llvm/Instructions.h"
+#include "llvm/ModuleProvider.h"
+#include "llvm/Analysis/Verifier.h"
 #include "llvm/ExecutionEngine/ExecutionEngine.h"
 #include "llvm/ExecutionEngine/GenericValue.h"
-
-
+#include <iostream>
 using namespace llvm;
 
-int main(int argc, char**argv) {
-
-  int n = argc > 1 ? atol(argv[1]) : 44;
-
-  // Create some module to put our function into it.
-  Module *M = new Module("test");
-
-
-  // We are about to create the "fib" function:
-  Function *FibF;
-
-  {
-    // first create type for the single argument of fib function: 
-    // the type is 'int ()'
-    std::vector<const Type*> ArgT(1);
-    ArgT[0] = Type::IntTy;
-
-    // now create full type of the "fib" function:
-    FunctionType *FibT = FunctionType::get(Type::IntTy, // type of result
-					   ArgT,
-					   /*not vararg*/false);
- 
-    // Now create the fib function entry and 
-    // insert this entry into module M
-    // (By passing a module as the last parameter to the Function constructor,
-    // it automatically gets appended to the Module.)
-    FibF = new Function(FibT, 
-			Function::ExternalLinkage, // maybe too much
-			"fib", M);
-
-    // Add a basic block to the function... (again, it automatically inserts
-    // because of the last argument.)
-    BasicBlock *BB = new BasicBlock("EntryBlock of fib function", FibF);
+static Function *CreateFibFunction(Module *M) {
+  // Create the fib function and insert it into module M.  This function is said
+  // to return an int and take an int parameter.
+  Function *FibF = M->getOrInsertFunction("fib", Type::IntTy, Type::IntTy, 0);
   
-    // Get pointers to the constants ...
-    Value *One = ConstantSInt::get(Type::IntTy, 1);
-    Value *Two = ConstantSInt::get(Type::IntTy, 2);
-
-    // Get pointers to the integer argument of the add1 function...
-    assert(FibF->abegin() != FibF->aend()); // Make sure there's an arg
-
-    Argument &ArgX = FibF->afront();  // Get the arg
-    ArgX.setName("AnArg");            // Give it a nice symbolic name for fun.
+  // Add a basic block to the function.
+  BasicBlock *BB = new BasicBlock("EntryBlock", FibF);
+  
+  // Get pointers to the constants.
+  Value *One = ConstantSInt::get(Type::IntTy, 1);
+  Value *Two = ConstantSInt::get(Type::IntTy, 2);
 
-    SetCondInst* CondInst 
-      = new SetCondInst( Instruction::SetLE, 
-			 &ArgX, Two );
+  // Get pointer to the integer argument of the add1 function...
+  Argument *ArgX = FibF->abegin();   // Get the arg.
+  ArgX->setName("AnArg");            // Give it a nice symbolic name for fun.
 
-    BB->getInstList().push_back(CondInst);
 
-    // Create the true_block
-    BasicBlock* true_bb = new BasicBlock("arg<=2");
+  // Create the true_block.
+  BasicBlock *RetBB = new BasicBlock("return", FibF);
+  // Create an exit block.
+  BasicBlock* RecurseBB = new BasicBlock("recurse", FibF);
 
+  // Create the "if (arg < 2) goto exitbb"
+  Value *CondInst = BinaryOperator::createSetLE(ArgX, Two, "cond", BB);
+  new BranchInst(RetBB, RecurseBB, CondInst, BB);
 
-    // Create the return instruction and add it 
-    // to the basic block for true case:
-    true_bb->getInstList().push_back(new ReturnInst(One));
-      
-    // Create an exit block
-    BasicBlock* exit_bb = new BasicBlock("arg>2");
-    
-    {
-
-      // create fib(x-1)
-      CallInst* CallFibX1;
-      {
-	// Create the sub instruction... does not insert...
-	Instruction *Sub 
-	  = BinaryOperator::create(Instruction::Sub, &ArgX, One,
-						"arg");       
-       
-	exit_bb->getInstList().push_back(Sub);
-
-	CallFibX1 = new CallInst(FibF, Sub, "fib(x-1)");
-	exit_bb->getInstList().push_back(CallFibX1);
-	 
-      }
-
-      // create fib(x-2)
-      CallInst* CallFibX2;
-      {
-	// Create the sub instruction... does not insert...
-	Instruction * Sub
-	  = BinaryOperator::create(Instruction::Sub, &ArgX, Two,
-						"arg");
-
-	exit_bb->getInstList().push_back(Sub);
-	CallFibX2 = new CallInst(FibF, Sub, "fib(x-2)");
-	exit_bb->getInstList().push_back(CallFibX2);
-	  
-      }
-
-      // Create the add instruction... does not insert...
-      Instruction *Add = 
-	BinaryOperator::create(Instruction::Add, 
-			       CallFibX1, CallFibX2, "addresult");
+  // Create: ret int 1
+  new ReturnInst(One, RetBB);
+  
+  // create fib(x-1)
+  Value *Sub = BinaryOperator::createSub(ArgX, One, "arg", RecurseBB);
+  Value *CallFibX1 = new CallInst(FibF, Sub, "fibx1", RecurseBB);
       
-      // explicitly insert it into the basic block...
-      exit_bb->getInstList().push_back(Add);
+  // create fib(x-2)
+  Sub = BinaryOperator::createSub(ArgX, Two, "arg", RecurseBB);
+  Value *CallFibX2 = new CallInst(FibF, Sub, "fibx2", RecurseBB);
+
+  // fib(x-1)+fib(x-2)
+  Value *Sum = BinaryOperator::createAdd(CallFibX1, CallFibX2,
+                                         "addresult", RecurseBB);
       
-      // Create the return instruction and add it to the basic block
-      exit_bb->getInstList().push_back(new ReturnInst(Add));      
-    }
+  // Create the return instruction and add it to the basic block
+  new ReturnInst(Sum, RecurseBB);
 
-    // Create a branch on the SetCond
-    BranchInst* br_inst = 
-      new BranchInst( true_bb, exit_bb, CondInst );
+  return FibF;
+}
 
-    BB->getInstList().push_back( br_inst );
-    FibF->getBasicBlockList().push_back(true_bb);
-    FibF->getBasicBlockList().push_back(exit_bb);
-  }
 
-  // Now we going to create JIT 
-  ExistingModuleProvider* MP = new ExistingModuleProvider(M);
-  ExecutionEngine* EE = ExecutionEngine::create( MP, false );
+int main(int argc, char **argv) {
+  int n = argc > 1 ? atol(argv[1]) : 24;
 
-  // Call the `foo' function with argument n:
-  std::vector<GenericValue> args(1);
-  args[0].IntVal = n;
+  // Create some module to put our function into it.
+  Module *M = new Module("test");
+
+  // We are about to create the "fib" function:
+  Function *FibF = CreateFibFunction(M);
 
+  // Now we going to create JIT 
+  ExistingModuleProvider *MP = new ExistingModuleProvider(M);
+  ExecutionEngine *EE = ExecutionEngine::create(MP, false);
 
-  std::clog << "verifying... ";
+  std::cerr << "verifying... ";
   if (verifyModule(*M)) {
-    std::cerr << argv[0]
-	      << ": assembly parsed, but does not verify as correct!\n";
+    std::cerr << argv[0] << ": Error constructing function!\n";
     return 1;
   }
-  else 
-    std::clog << "OK\n";
 
+  std::cerr << "OK\n";
+  std::cerr << "We just constructed this LLVM module:\n\n---------\n" << *M;
+  std::cerr << "---------\nstarting fibonacci(" 
+	    << n << ") with JIT...\n";
 
-  std::clog << "We just constructed this LLVM module:\n\n---------\n" << *M;
-  std::clog << "---------\nstarting fibonacci(" 
-	    << n << ") with JIT...\n" << std::flush;
-
-  GenericValue gv = EE->runFunction(FibF, args);
-
-  // import result of execution:
-  std::cout << "Result: " << gv.IntVal << std:: endl;
+  // Call the `foo' function with argument n:
+  std::vector<GenericValue> Args(1);
+  args[0].IntVal = n;
+  GenericValue GV = EE->runFunction(FibF, Args);
 
+  // import result of execution
+  std::cout << "Result: " << GV.IntVal << "\n";
   return 0;
 }