1 //===- Optimize.cpp - Optimize a complete program -------------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // 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 //Don't verify at the end
36 static cl::opt<bool> DontVerify("disable-verify", cl::ReallyHidden);
38 // Optimization Enumeration
39 enum OptimizationLevels {
44 OPT_AGGRESSIVE_LINK_TIME = 5
47 // Optimization Options
48 static cl::opt<OptimizationLevels> OptLevel(
49 cl::desc("Choose level of optimization to apply:"),
50 cl::init(OPT_FAST_COMPILE), cl::values(
51 clEnumValN(OPT_FAST_COMPILE,"O0",
52 "An alias for the -O1 option."),
53 clEnumValN(OPT_FAST_COMPILE,"O1",
54 "Optimize for linking speed, not execution speed."),
55 clEnumValN(OPT_SIMPLE,"O2",
56 "Perform only required/minimal optimizations"),
57 clEnumValN(OPT_AGGRESSIVE,"O3",
58 "An alias for the -O2 option."),
59 clEnumValN(OPT_LINK_TIME,"O4",
60 "Perform standard link time optimizations"),
61 clEnumValN(OPT_AGGRESSIVE_LINK_TIME,"O5",
62 "Perform aggressive link time optimizations"),
67 static cl::opt<bool> DisableInline("disable-inlining",
68 cl::desc("Do not run the inliner pass"));
71 DisableOptimizations("disable-opt",
72 cl::desc("Do not run any optimization passes"));
74 static cl::opt<bool> DisableInternalize("disable-internalize",
75 cl::desc("Do not mark all symbols as internal"));
77 static cl::opt<bool> VerifyEach("verify-each",
78 cl::desc("Verify intermediate results of all passes"));
80 static cl::alias ExportDynamic("export-dynamic",
81 cl::aliasopt(DisableInternalize),
82 cl::desc("Alias for -disable-internalize"));
84 static cl::opt<bool> Strip("strip-all",
85 cl::desc("Strip all symbol info from executable"));
87 static cl::alias A0("s", cl::desc("Alias for --strip-all"),
90 static cl::opt<bool> StripDebug("strip-debug",
91 cl::desc("Strip debugger symbol info from executable"));
93 static cl::alias A1("S", cl::desc("Alias for --strip-debug"),
94 cl::aliasopt(StripDebug));
96 // A utility function that adds a pass to the pass manager but will also add
97 // a verifier pass after if we're supposed to verify.
98 static inline void addPass(PassManager &PM, Pass *P) {
99 // Add the pass to the pass manager...
102 // If we are verifying all of the intermediate steps, add the verifier...
104 PM.add(createVerifierPass());
109 /// Optimize - Perform link time optimizations. This will run the scalar
110 /// optimizations, any loaded plugin-optimization modules, and then the
111 /// inter-procedural optimizations if applicable.
112 void Optimize(Module* M) {
114 // Instantiate the pass manager to organize the passes.
117 // If we're verifying, start off with a verification pass.
119 Passes.add(createVerifierPass());
121 // Add an appropriate TargetData instance for this module...
122 addPass(Passes, new TargetData(M));
124 if (!DisableOptimizations) {
125 // Now that composite has been compiled, scan through the module, looking
126 // for a main function. If main is defined, mark all other functions
128 if (!DisableInternalize)
129 addPass(Passes, createInternalizePass(true));
131 // Propagate constants at call sites into the functions they call. This
132 // opens opportunities for globalopt (and inlining) by substituting function
133 // pointers passed as arguments to direct uses of functions.
134 addPass(Passes, createIPSCCPPass());
136 // Now that we internalized some globals, see if we can hack on them!
137 addPass(Passes, createGlobalOptimizerPass());
139 // Linking modules together can lead to duplicated global constants, only
140 // keep one copy of each constant...
141 addPass(Passes, createConstantMergePass());
143 // Remove unused arguments from functions...
144 addPass(Passes, createDeadArgEliminationPass());
146 // Reduce the code after globalopt and ipsccp. Both can open up significant
147 // simplification opportunities, and both can propagate functions through
148 // function pointers. When this happens, we often have to resolve varargs
149 // calls, etc, so let instcombine do this.
150 addPass(Passes, createInstructionCombiningPass());
153 addPass(Passes, createFunctionInliningPass()); // Inline small functions
155 addPass(Passes, createPruneEHPass()); // Remove dead EH info
156 addPass(Passes, createGlobalOptimizerPass()); // Optimize globals again.
157 addPass(Passes, createGlobalDCEPass()); // Remove dead functions
159 // If we didn't decide to inline a function, check to see if we can
160 // transform it to pass arguments by value instead of by reference.
161 addPass(Passes, createArgumentPromotionPass());
163 // The IPO passes may leave cruft around. Clean up after them.
164 addPass(Passes, createInstructionCombiningPass());
165 addPass(Passes, createJumpThreadingPass()); // Thread jumps.
166 addPass(Passes, createScalarReplAggregatesPass()); // Break up allocas
168 // Run a few AA driven optimizations here and now, to cleanup the code.
169 addPass(Passes, createGlobalsModRefPass()); // IP alias analysis
171 addPass(Passes, createLICMPass()); // Hoist loop invariants
172 addPass(Passes, createGVNPass()); // Remove redundancies
173 addPass(Passes, createMemCpyOptPass()); // Remove dead memcpy's
174 addPass(Passes, createDeadStoreEliminationPass()); // Nuke dead stores
176 // Cleanup and simplify the code after the scalar optimizations.
177 addPass(Passes, createInstructionCombiningPass());
179 addPass(Passes, createJumpThreadingPass()); // Thread jumps.
181 // Delete basic blocks, which optimization passes may have killed...
182 addPass(Passes, createCFGSimplificationPass());
184 // Now that we have optimized the program, discard unreachable functions...
185 addPass(Passes, createGlobalDCEPass());
188 // If the -s or -S command line options were specified, strip the symbols out
189 // of the resulting program to make it smaller. -s and -S are GNU ld options
190 // that we are supporting; they alias -strip-all and -strip-debug.
191 if (Strip || StripDebug)
192 addPass(Passes, createStripSymbolsPass(StripDebug && !Strip));
194 // Create a new optimization pass for each one specified on the command line
195 std::auto_ptr<TargetMachine> target;
196 for (unsigned i = 0; i < OptimizationList.size(); ++i) {
197 const PassInfo *Opt = OptimizationList[i];
198 if (Opt->getNormalCtor())
199 addPass(Passes, Opt->getNormalCtor()());
201 std::cerr << "llvm-ld: cannot create pass: " << Opt->getPassName()
205 // The user's passes may leave cruft around. Clean up after them them but
206 // only if we haven't got DisableOptimizations set
207 if (!DisableOptimizations) {
208 addPass(Passes, createInstructionCombiningPass());
209 addPass(Passes, createCFGSimplificationPass());
210 addPass(Passes, createDeadCodeEliminationPass());
211 addPass(Passes, createGlobalDCEPass());
214 // Make sure everything is still good.
216 Passes.add(createVerifierPass());
218 // Run our queue of passes all at once now, efficiently.