1 //===- Optimize.cpp - Optimize a complete program -------------------------===//
3 // The LLVM Compiler Infrastructure
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.
8 //===----------------------------------------------------------------------===//
10 // This file implements all optimization of the linked module for llvm-ld.
12 //===----------------------------------------------------------------------===//
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"
31 // Pass Name Options as generated by the PassNameParser
32 static cl::list<const PassInfo*, bool, PassNameParser>
33 OptimizationList(cl::desc("Optimizations available:"));
35 // Optimization Enumeration
36 enum OptimizationLevels {
41 OPT_AGGRESSIVE_LINK_TIME = 5
44 // Optimization Options
45 static 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"),
64 static cl::opt<bool> DisableInline("disable-inlining",
65 cl::desc("Do not run the inliner pass"));
68 DisableOptimizations("disable-opt",
69 cl::desc("Do not run any optimization passes"));
71 static cl::opt<bool> DisableInternalize("disable-internalize",
72 cl::desc("Do not mark all symbols as internal"));
74 static cl::opt<bool> VerifyEach("verify-each",
75 cl::desc("Verify intermediate results of all passes"));
77 static cl::alias ExportDynamic("export-dynamic",
78 cl::aliasopt(DisableInternalize),
79 cl::desc("Alias for -disable-internalize"));
81 static cl::opt<bool> Strip("strip-all",
82 cl::desc("Strip all symbol info from executable"));
84 static cl::alias A0("s", cl::desc("Alias for --strip-all"),
87 static cl::opt<bool> StripDebug("strip-debug",
88 cl::desc("Strip debugger symbol info from executable"));
90 static cl::alias A1("S", cl::desc("Alias for --strip-debug"),
91 cl::aliasopt(StripDebug));
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.
95 static inline void addPass(PassManager &PM, Pass *P) {
96 // Add the pass to the pass manager...
99 // If we are verifying all of the intermediate steps, add the verifier...
101 PM.add(createVerifierPass());
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.
109 void Optimize(Module* M) {
111 // Instantiate the pass manager to organize the passes.
114 // If we're verifying, start off with a verification pass.
116 Passes.add(createVerifierPass());
118 // Add an appropriate TargetData instance for this module...
119 addPass(Passes, new TargetData(M));
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
125 addPass(Passes, createInternalizePass(!DisableInternalize));
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());
132 // Now that we internalized some globals, see if we can hack on them!
133 addPass(Passes, createGlobalOptimizerPass());
135 // Linking modules together can lead to duplicated global constants, only
136 // keep one copy of each constant...
137 addPass(Passes, createConstantMergePass());
139 // Remove unused arguments from functions...
140 addPass(Passes, createDeadArgEliminationPass());
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());
149 addPass(Passes, createFunctionInliningPass()); // Inline small functions
151 addPass(Passes, createPruneEHPass()); // Remove dead EH info
152 addPass(Passes, createGlobalOptimizerPass()); // Optimize globals again.
153 addPass(Passes, createGlobalDCEPass()); // Remove dead functions
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());
159 // The IPO passes may leave cruft around. Clean up after them.
160 addPass(Passes, createInstructionCombiningPass());
162 addPass(Passes, createScalarReplAggregatesPass()); // Break up allocas
164 // Run a few AA driven optimizations here and now, to cleanup the code.
165 addPass(Passes, createGlobalsModRefPass()); // IP alias analysis
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
172 // Cleanup and simplify the code after the scalar optimizations.
173 addPass(Passes, createInstructionCombiningPass());
175 // Delete basic blocks, which optimization passes may have killed...
176 addPass(Passes, createCFGSimplificationPass());
178 // Now that we have optimized the program, discard unreachable functions...
179 addPass(Passes, createGlobalDCEPass());
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));
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()());
195 std::cerr << "llvm-ld: cannot create pass: " << Opt->getPassName()
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());
208 // Make sure everything is still good.
209 Passes.add(createVerifierPass());
211 // Run our queue of passes all at once now, efficiently.