Optimize.cpp revision c8c5752b2fcc9131358905e7af75d51dd84861b9 
1//===- Optimize.cpp - Optimize a complete program -------------------------===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file was developed by Reid Spencer and is distributed under the
6// University of Illinois Open Source License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This file implements all optimization of the linked module for llvm-ld.
11//
12//===----------------------------------------------------------------------===//
13
14#include "llvm/Module.h"
15#include "llvm/PassManager.h"
16#include "llvm/Analysis/LoadValueNumbering.h"
17#include "llvm/Analysis/Passes.h"
18#include "llvm/Analysis/LoopPass.h"
19#include "llvm/Analysis/Verifier.h"
20#include "llvm/Support/CommandLine.h"
21#include "llvm/System/DynamicLibrary.h"
22#include "llvm/Target/TargetData.h"
23#include "llvm/Target/TargetMachine.h"
24#include "llvm/Transforms/IPO.h"
25#include "llvm/Transforms/Scalar.h"
26#include "llvm/Support/PassNameParser.h"
27#include "llvm/Support/PluginLoader.h"
28#include <iostream>
29using namespace llvm;
30
31// Pass Name Options as generated by the PassNameParser
32static cl::list<const PassInfo*, bool, PassNameParser>
33  OptimizationList(cl::desc("Optimizations available:"));
34
35// Optimization Enumeration
36enum OptimizationLevels {
37  OPT_FAST_COMPILE         = 1,
38  OPT_SIMPLE               = 2,
39  OPT_AGGRESSIVE           = 3,
40  OPT_LINK_TIME            = 4,
41  OPT_AGGRESSIVE_LINK_TIME = 5
42};
43
44// Optimization Options
45static cl::opt<OptimizationLevels> OptLevel(
46  cl::desc("Choose level of optimization to apply:"),
47  cl::init(OPT_FAST_COMPILE), cl::values(
48    clEnumValN(OPT_FAST_COMPILE,"O0",
49      "An alias for the -O1 option."),
50    clEnumValN(OPT_FAST_COMPILE,"O1",
51      "Optimize for linking speed, not execution speed."),
52    clEnumValN(OPT_SIMPLE,"O2",
53      "Perform only required/minimal optimizations"),
54    clEnumValN(OPT_AGGRESSIVE,"O3",
55      "An alias for the -O2 option."),
56    clEnumValN(OPT_LINK_TIME,"O4",
57      "Perform standard link time optimizations"),
58    clEnumValN(OPT_AGGRESSIVE_LINK_TIME,"O5",
59      "Perform aggressive link time optimizations"),
60    clEnumValEnd
61  )
62);
63
64static cl::opt<bool> DisableInline("disable-inlining",
65  cl::desc("Do not run the inliner pass"));
66
67static cl::opt<bool>
68DisableOptimizations("disable-opt",
69  cl::desc("Do not run any optimization passes"));
70
71static cl::opt<bool> DisableInternalize("disable-internalize",
72  cl::desc("Do not mark all symbols as internal"));
73
74static cl::opt<bool> VerifyEach("verify-each",
75 cl::desc("Verify intermediate results of all passes"));
76
77static cl::alias ExportDynamic("export-dynamic",
78  cl::aliasopt(DisableInternalize),
79  cl::desc("Alias for -disable-internalize"));
80
81static cl::opt<bool> Strip("strip-all",
82  cl::desc("Strip all symbol info from executable"));
83
84static cl::alias A0("s", cl::desc("Alias for --strip-all"),
85  cl::aliasopt(Strip));
86
87static cl::opt<bool> StripDebug("strip-debug",
88  cl::desc("Strip debugger symbol info from executable"));
89
90static cl::alias A1("S", cl::desc("Alias for --strip-debug"),
91  cl::aliasopt(StripDebug));
92
93// A utility function that adds a pass to the pass manager but will also add
94// a verifier pass after if we're supposed to verify.
95static inline void addPass(PassManager &PM, Pass *P) {
96  // Add the pass to the pass manager...
97  PM.add(P);
98
99  // If we are verifying all of the intermediate steps, add the verifier...
100  if (VerifyEach)
101    PM.add(createVerifierPass());
102}
103
104namespace llvm {
105
106/// Optimize - Perform link time optimizations. This will run the scalar
107/// optimizations, any loaded plugin-optimization modules, and then the
108/// inter-procedural optimizations if applicable.
109void Optimize(Module* M) {
110
111  // Instantiate the pass manager to organize the passes.
112  PassManager Passes;
113
114  // If we're verifying, start off with a verification pass.
115  if (VerifyEach)
116    Passes.add(createVerifierPass());
117
118  // Add an appropriate TargetData instance for this module...
119  addPass(Passes, new TargetData(M));
120
121  if (!DisableOptimizations) {
122    // Now that composite has been compiled, scan through the module, looking
123    // for a main function.  If main is defined, mark all other functions
124    // internal.
125    addPass(Passes, createInternalizePass(!DisableInternalize));
126
127    // Propagate constants at call sites into the functions they call.  This
128    // opens opportunities for globalopt (and inlining) by substituting function
129    // pointers passed as arguments to direct uses of functions.
130    addPass(Passes, createIPSCCPPass());
131
132    // Now that we internalized some globals, see if we can hack on them!
133    addPass(Passes, createGlobalOptimizerPass());
134
135    // Linking modules together can lead to duplicated global constants, only
136    // keep one copy of each constant...
137    addPass(Passes, createConstantMergePass());
138
139    // Remove unused arguments from functions...
140    addPass(Passes, createDeadArgEliminationPass());
141
142    // Reduce the code after globalopt and ipsccp.  Both can open up significant
143    // simplification opportunities, and both can propagate functions through
144    // function pointers.  When this happens, we often have to resolve varargs
145    // calls, etc, so let instcombine do this.
146    addPass(Passes, createInstructionCombiningPass());
147
148    if (!DisableInline)
149      addPass(Passes, createFunctionInliningPass()); // Inline small functions
150
151    addPass(Passes, createPruneEHPass());            // Remove dead EH info
152    addPass(Passes, createGlobalOptimizerPass());    // Optimize globals again.
153    addPass(Passes, createGlobalDCEPass());          // Remove dead functions
154
155    // If we didn't decide to inline a function, check to see if we can
156    // transform it to pass arguments by value instead of by reference.
157    addPass(Passes, createArgumentPromotionPass());
158
159    // The IPO passes may leave cruft around.  Clean up after them.
160    addPass(Passes, createInstructionCombiningPass());
161
162    addPass(Passes, createScalarReplAggregatesPass()); // Break up allocas
163
164    // Run a few AA driven optimizations here and now, to cleanup the code.
165    addPass(Passes, createGlobalsModRefPass());      // IP alias analysis
166
167    addPass(Passes, createLICMPass());               // Hoist loop invariants
168    addPass(Passes, createLoadValueNumberingPass()); // GVN for load instrs
169    addPass(Passes, createGCSEPass());               // Remove common subexprs
170    addPass(Passes, createDeadStoreEliminationPass()); // Nuke dead stores
171
172    // Cleanup and simplify the code after the scalar optimizations.
173    addPass(Passes, createInstructionCombiningPass());
174
175    // Delete basic blocks, which optimization passes may have killed...
176    addPass(Passes, createCFGSimplificationPass());
177
178    // Now that we have optimized the program, discard unreachable functions...
179    addPass(Passes, createGlobalDCEPass());
180  }
181
182  // If the -s or -S command line options were specified, strip the symbols out
183  // of the resulting program to make it smaller.  -s and -S are GNU ld options
184  // that we are supporting; they alias -strip-all and -strip-debug.
185  if (Strip || StripDebug)
186    addPass(Passes, createStripSymbolsPass(StripDebug && !Strip));
187
188  // Create a new optimization pass for each one specified on the command line
189  std::auto_ptr<TargetMachine> target;
190  for (unsigned i = 0; i < OptimizationList.size(); ++i) {
191    const PassInfo *Opt = OptimizationList[i];
192    if (Opt->getNormalCtor())
193      addPass(Passes, Opt->getNormalCtor()());
194    else
195      std::cerr << "llvm-ld: cannot create pass: " << Opt->getPassName()
196                << "\n";
197  }
198
199  // The user's passes may leave cruft around. Clean up after them them but
200  // only if we haven't got DisableOptimizations set
201  if (!DisableOptimizations) {
202    addPass(Passes, createInstructionCombiningPass());
203    addPass(Passes, createCFGSimplificationPass());
204    addPass(Passes, createDeadCodeEliminationPass());
205    addPass(Passes, createGlobalDCEPass());
206  }
207
208  // Make sure everything is still good.
209  Passes.add(createVerifierPass());
210
211  // Run our queue of passes all at once now, efficiently.
212  Passes.run(*M);
213}
214
215}
216