First cut at implementing generic link-time Optimization

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@18047 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/tools/llvm-ld/Optimize.cpp b/tools/llvm-ld/Optimize.cpp
new file mode 100644 (file)
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+++ b/tools/llvm-ld/Optimize.cpp
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+//===- Optimize.cpp - Optimize a complete program -------------------------===//
+// 
+//                     The LLVM Compiler Infrastructure
+//
+// This file was developed by Reid Spencer and is distributed under the 
+// University of Illinois Open Source License. See LICENSE.TXT for details.
+// 
+//===----------------------------------------------------------------------===//
+//
+// This file implements all optimization of the linked module for llvm-ld.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Module.h"
+#include "llvm/PassManager.h"
+#include "llvm/Analysis/LoadValueNumbering.h"
+#include "llvm/Analysis/Passes.h"
+#include "llvm/Analysis/Verifier.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/System/DynamicLibrary.h"
+#include "llvm/Target/TargetData.h"
+#include "llvm/Transforms/IPO.h"
+#include "llvm/Transforms/Scalar.h"
+using namespace llvm;
+
+// Optimization Options
+
+enum OptimizationLevels {
+  OPT_FAST_COMPILE         = 1,
+  OPT_SIMPLE               = 2,
+  OPT_AGGRESSIVE           = 3,
+  OPT_LINK_TIME            = 4,
+  OPT_AGGRESSIVE_LINK_TIME = 5
+};
+
+static cl::opt<OptimizationLevels> OptLevel(
+  cl::desc("Choose level of optimization to apply:"),
+  cl::init(OPT_FAST_COMPILE), cl::values(
+    clEnumValN(OPT_FAST_COMPILE,"O0",
+      "An alias for the -O1 option."),
+    clEnumValN(OPT_FAST_COMPILE,"O1",
+      "Optimize for linking speed, not execution speed."),
+    clEnumValN(OPT_SIMPLE,"O2",
+      "Perform only required/minimal optimizations"),
+    clEnumValN(OPT_AGGRESSIVE,"O3",
+      "An alias for the -O2 option."),
+    clEnumValN(OPT_LINK_TIME,"O4",
+      "Perform standard link time optimizations"),
+    clEnumValN(OPT_AGGRESSIVE_LINK_TIME,"O5",
+      "Perform aggressive link time optimizations"),
+    clEnumValEnd
+  )
+);
+
+static cl::opt<bool> DisableInline("disable-inlining", 
+  cl::desc("Do not run the inliner pass"));
+
+static cl::opt<bool>
+DisableOptimizations("disable-opt",
+  cl::desc("Do not run any optimization passes"));
+
+static cl::opt<bool> DisableInternalize("disable-internalize",
+  cl::desc("Do not mark all symbols as internal"));
+
+static cl::opt<bool> Verify("verify", 
+  cl::desc("Verify intermediate results of all passes"));
+
+static cl::opt<bool> Strip("s", 
+  cl::desc("Strip symbol info from executable"));
+
+static cl::alias ExportDynamic("export-dynamic", 
+  cl::aliasopt(DisableInternalize),
+  cl::desc("Alias for -disable-internalize"));
+
+static cl::list<std::string> LoadableModules("load",
+  cl::value_desc("path to loadable optimization module"),
+  cl::desc("Load an optimization module and run it"));
+
+// A utility function that adds a pass to the pass manager but will also add
+// a verifier pass after if we're supposed to verify.
+static inline void addPass(PassManager &PM, Pass *P) {
+  // Add the pass to the pass manager...
+  PM.add(P);
+  
+  // If we are verifying all of the intermediate steps, add the verifier...
+  if (Verify) 
+    PM.add(createVerifierPass());
+}
+
+namespace llvm {
+
+/// Optimize - Perform link time optimizations. This will run the scalar 
+/// optimizations, any loaded plugin-optimization modules, and then the 
+/// inter-procedural optimizations if applicable.
+void Optimize(Module* M) {
+
+  // Instantiate the pass manager to organize the passes.
+  PassManager Passes;
+
+  // If we're verifying, start off with a verification pass.
+  if (Verify) 
+    Passes.add(createVerifierPass());
+
+  // Add an appropriate TargetData instance for this module...
+  addPass(Passes, new TargetData("gccld", M));
+
+  // Often if the programmer does not specify proper prototypes for the
+  // functions they are calling, they end up calling a vararg version of the
+  // function that does not get a body filled in (the real function has typed
+  // arguments).  This pass merges the two functions.
+  addPass(Passes, createFunctionResolvingPass());
+
+  if (!DisableOptimizations) {
+    if (!DisableInternalize) {
+      // Now that composite has been compiled, scan through the module, looking
+      // for a main function.  If main is defined, mark all other functions
+      // internal.
+      addPass(Passes, createInternalizePass());
+    }
+
+    // Now that we internalized some globals, see if we can hack on them!
+    addPass(Passes, createGlobalOptimizerPass());
+
+    // Linking modules together can lead to duplicated global constants, only
+    // keep one copy of each constant...
+    addPass(Passes, createConstantMergePass());
+
+    // If the -s command line option was specified, strip the symbols out of the
+    // resulting program to make it smaller.  -s is a GCC option that we are
+    // supporting.
+    if (Strip)
+      addPass(Passes, createSymbolStrippingPass());
+
+    // Propagate constants at call sites into the functions they call.
+    addPass(Passes, createIPConstantPropagationPass());
+
+    // Remove unused arguments from functions...
+    addPass(Passes, createDeadArgEliminationPass());
+
+    if (!DisableInline)
+      addPass(Passes, createFunctionInliningPass()); // Inline small functions
+
+    addPass(Passes, createPruneEHPass());            // Remove dead EH info
+    addPass(Passes, createGlobalDCEPass());          // Remove dead functions
+
+    // If we didn't decide to inline a function, check to see if we can
+    // transform it to pass arguments by value instead of by reference.
+    addPass(Passes, createArgumentPromotionPass());
+
+    // The IPO passes may leave cruft around.  Clean up after them.
+    addPass(Passes, createInstructionCombiningPass());
+
+    addPass(Passes, createScalarReplAggregatesPass()); // Break up allocas
+
+    // Run a few AA driven optimizations here and now, to cleanup the code.
+    addPass(Passes, createGlobalsModRefPass());      // IP alias analysis
+
+    addPass(Passes, createLICMPass());               // Hoist loop invariants
+    addPass(Passes, createLoadValueNumberingPass()); // GVN for load instrs
+    addPass(Passes, createGCSEPass());               // Remove common subexprs
+    addPass(Passes, createDeadStoreEliminationPass()); // Nuke dead stores
+
+    // Cleanup and simplify the code after the scalar optimizations.
+    addPass(Passes, createInstructionCombiningPass());
+
+    // Delete basic blocks, which optimization passes may have killed...
+    addPass(Passes, createCFGSimplificationPass());
+
+    // Now that we have optimized the program, discard unreachable functions...
+    addPass(Passes, createGlobalDCEPass());
+  }
+
+  std::vector<std::string> plugins = LoadableModules;
+  for (std::vector<std::string>::iterator I = plugins.begin(), 
+      E = plugins.end(); I != E; ++I) {
+    sys::DynamicLibrary dll(I->c_str());
+    typedef void (*OptimizeFunc)(PassManager&,int);
+    OptimizeFunc OF = OptimizeFunc(
+        dll.GetAddressOfSymbol("RunOptimizations"));
+    if (OF == 0) {
+      throw std::string("Optimization Module '") + *I + 
+        "' is missing the RunOptimizations symbol";
+    }
+    (*OF)(Passes,OptLevel);
+  }
+
+  // Make sure everything is still good.
+  Passes.add(createVerifierPass());
+
+  // Run our queue of passes all at once now, efficiently.
+  Passes.run(*M);
+}
+
+}