1 //===-- Passes.h - Target independent code generation passes ----*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file was developed by the LLVM research group and is distributed under
6 // the University of Illinois Open Source License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file defines interfaces to access the target independent code generation
11 // passes provided by the LLVM backend.
13 //===----------------------------------------------------------------------===//
15 #ifndef LLVM_CODEGEN_PASSES_H
16 #define LLVM_CODEGEN_PASSES_H
26 class RegisterCoalescer;
28 /// createUnreachableBlockEliminationPass - The LLVM code generator does not
29 /// work well with unreachable basic blocks (what live ranges make sense for a
30 /// block that cannot be reached?). As such, a code generator should either
31 /// not instruction select unreachable blocks, or it can run this pass as it's
32 /// last LLVM modifying pass to clean up blocks that are not reachable from
34 FunctionPass *createUnreachableBlockEliminationPass();
36 /// MachineFunctionPrinter pass - This pass prints out the machine function to
37 /// standard error, as a debugging tool.
38 FunctionPass *createMachineFunctionPrinterPass(std::ostream *OS,
39 const std::string &Banner ="");
41 /// PHIElimination pass - This pass eliminates machine instruction PHI nodes
42 /// by inserting copy instructions. This destroys SSA information, but is the
43 /// desired input for some register allocators. This pass is "required" by
44 /// these register allocator like this: AU.addRequiredID(PHIEliminationID);
46 extern const PassInfo *PHIEliminationID;
48 /// StrongPHIElimination pass - This pass eliminates machine instruction PHI
49 /// nodes by inserting copy instructions. This destroys SSA information, but
50 /// is the desired input for some register allocators. This pass is
51 /// "required" by these register allocator like this:
52 /// AU.addRequiredID(PHIEliminationID);
53 /// This pass is still in development
54 extern const PassInfo *StrongPHIEliminationID;
56 /// SimpleRegisterCoalescing pass. Aggressively coalesces every register
59 extern const PassInfo *SimpleRegisterCoalescingID;
61 /// BreakCriticalMachineEdges pass. Breaks critical edges between
62 /// machine basic blocks.
63 extern const PassInfo *BreakCriticalMachineEdgesID;
65 /// TwoAddressInstruction pass - This pass reduces two-address instructions to
66 /// use two operands. This destroys SSA information but it is desired by
67 /// register allocators.
68 extern const PassInfo *TwoAddressInstructionPassID;
70 /// Creates a register allocator as the user specified on the command line.
72 FunctionPass *createRegisterAllocator();
74 /// SimpleRegisterAllocation Pass - This pass converts the input machine code
75 /// from SSA form to use explicit registers by spilling every register. Wow,
78 FunctionPass *createSimpleRegisterAllocator();
80 /// LocalRegisterAllocation Pass - This pass register allocates the input code
81 /// a basic block at a time, yielding code better than the simple register
82 /// allocator, but not as good as a global allocator.
84 FunctionPass *createLocalRegisterAllocator();
86 /// BigBlockRegisterAllocation Pass - The BigBlock register allocator
87 /// munches single basic blocks at a time, like the local register
88 /// allocator. While the BigBlock allocator is a little slower, and uses
89 /// somewhat more memory than the local register allocator, it tends to
90 /// yield the best allocations (of any of the allocators) for blocks that
91 /// have hundreds or thousands of instructions in sequence.
93 FunctionPass *createBigBlockRegisterAllocator();
95 /// LinearScanRegisterAllocation Pass - This pass implements the linear scan
96 /// register allocation algorithm, a global register allocator.
98 FunctionPass *createLinearScanRegisterAllocator();
100 /// SimpleRegisterCoalescing Pass - Coalesce all copies possible. Can run
101 /// independently of the register allocator.
103 RegisterCoalescer *createSimpleRegisterCoalescer();
105 /// PrologEpilogCodeInserter Pass - This pass inserts prolog and epilog code,
106 /// and eliminates abstract frame references.
108 FunctionPass *createPrologEpilogCodeInserter();
110 /// LowerSubregs Pass - This pass lowers subregs to register-register copies
111 /// which yields suboptimal, but correct code if the register allocator
112 /// cannot coalesce all subreg operations during allocation.
114 FunctionPass *createLowerSubregsPass();
116 /// createPostRAScheduler - under development.
117 FunctionPass *createPostRAScheduler();
119 /// BranchFolding Pass - This pass performs machine code CFG based
120 /// optimizations to delete branches to branches, eliminate branches to
121 /// successor blocks (creating fall throughs), and eliminating branches over
123 FunctionPass *createBranchFoldingPass(bool DefaultEnableTailMerge);
125 /// IfConverter Pass - This pass performs machine code if conversion.
126 FunctionPass *createIfConverterPass();
128 /// DebugLabelFoldingPass - This pass prunes out redundant debug labels. This
129 /// allows a debug emitter to determine if the range of two labels is empty,
130 /// by seeing if the labels map to the same reduced label.
131 FunctionPass *createDebugLabelFoldingPass();
133 /// MachineCodeDeletion Pass - This pass deletes all of the machine code for
134 /// the current function, which should happen after the function has been
135 /// emitted to a .s file or to memory.
136 FunctionPass *createMachineCodeDeleter();
138 /// getRegisterAllocator - This creates an instance of the register allocator
140 FunctionPass *getRegisterAllocator(TargetMachine &T);
142 } // End llvm namespace