1 //===-- Scalar.h - Scalar Transformations -----------------------*- 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 header file defines prototypes for accessor functions that expose passes
11 // in the Scalar transformations library.
13 //===----------------------------------------------------------------------===//
15 #ifndef LLVM_TRANSFORMS_SCALAR_H
16 #define LLVM_TRANSFORMS_SCALAR_H
22 class GetElementPtrInst;
26 //===----------------------------------------------------------------------===//
28 // RaisePointerReferences - Try to eliminate as many pointer arithmetic
29 // expressions as possible, by converting expressions to use getelementptr and
32 Pass *createRaisePointerReferencesPass();
34 //===----------------------------------------------------------------------===//
36 // Constant Propagation Pass - A worklist driven constant propagation pass
38 Pass *createConstantPropagationPass();
41 //===----------------------------------------------------------------------===//
43 // Sparse Conditional Constant Propagation Pass
45 Pass *createSCCPPass();
48 //===----------------------------------------------------------------------===//
50 // DeadInstElimination - This pass quickly removes trivially dead instructions
51 // without modifying the CFG of the function. It is a BasicBlockPass, so it
52 // runs efficiently when queued next to other BasicBlockPass's.
54 Pass *createDeadInstEliminationPass();
57 //===----------------------------------------------------------------------===//
59 // DeadCodeElimination - This pass is more powerful than DeadInstElimination,
60 // because it is worklist driven that can potentially revisit instructions when
61 // their other instructions become dead, to eliminate chains of dead
64 Pass *createDeadCodeEliminationPass();
67 //===----------------------------------------------------------------------===//
69 // AggressiveDCE - This pass uses the SSA based Aggressive DCE algorithm. This
70 // algorithm assumes instructions are dead until proven otherwise, which makes
71 // it more successful are removing non-obviously dead instructions.
73 Pass *createAggressiveDCEPass();
76 //===----------------------------------------------------------------------===//
78 // Scalar Replacement of Aggregates - Break up alloca's of aggregates into
79 // multiple allocas if possible.
81 Pass *createScalarReplAggregatesPass();
83 //===----------------------------------------------------------------------===//
85 // DecomposeMultiDimRefs - Convert multi-dimensional references consisting of
86 // any combination of 2 or more array and structure indices into a sequence of
87 // instructions (using getelementpr and cast) so that each instruction has at
88 // most one index (except structure references, which need an extra leading
91 // This pass decomposes all multi-dimensional references in a function.
92 FunctionPass *createDecomposeMultiDimRefsPass();
94 // This function decomposes a single instance of such a reference.
95 // Return value: true if the instruction was replaced; false otherwise.
97 bool DecomposeArrayRef(GetElementPtrInst* GEP);
99 //===----------------------------------------------------------------------===//
101 // GCSE - This pass is designed to be a very quick global transformation that
102 // eliminates global common subexpressions from a function. It does this by
103 // examining the SSA value graph of the function, instead of doing slow
104 // bit-vector computations.
106 FunctionPass *createGCSEPass();
109 //===----------------------------------------------------------------------===//
111 // InductionVariableSimplify - Transform induction variables in a program to all
112 // use a single canonical induction variable per loop.
114 Pass *createIndVarSimplifyPass();
117 //===----------------------------------------------------------------------===//
119 // InstructionCombining - Combine instructions to form fewer, simple
120 // instructions. This pass does not modify the CFG, and has a tendency to
121 // make instructions dead, so a subsequent DCE pass is useful.
123 // This pass combines things like:
124 // %Y = add int 1, %X
125 // %Z = add int 1, %Y
127 // %Z = add int 2, %X
129 Pass *createInstructionCombiningPass();
132 //===----------------------------------------------------------------------===//
134 // LICM - This pass is a simple natural loop based loop invariant code motion
137 FunctionPass *createLICMPass();
140 //===----------------------------------------------------------------------===//
142 // PiNodeInsertion - This pass inserts single entry Phi nodes into basic blocks
143 // that are preceeded by a conditional branch, where the branch gives
144 // information about the operands of the condition. For example, this C code:
145 // if (x == 0) { ... = x + 4;
148 // x2 = phi(x); // Node that can hold data flow information about X
151 // Since the direction of the condition branch gives information about X itself
152 // (whether or not it is zero), some passes (like value numbering or ABCD) can
153 // use the inserted Phi/Pi nodes as a place to attach information, in this case
154 // saying that X has a value of 0 in this scope. The power of this analysis
155 // information is that "in the scope" translates to "for all uses of x2".
157 // This special form of Phi node is refered to as a Pi node, following the
158 // terminology defined in the "Array Bounds Checks on Demand" paper.
160 Pass *createPiNodeInsertionPass();
163 //===----------------------------------------------------------------------===//
165 // This pass is used to promote memory references to be register references. A
166 // simple example of the transformation performed by this pass is:
169 // %X = alloca int, uint 1 ret int 42
170 // store int 42, int *%X
174 Pass *createPromoteMemoryToRegister();
177 //===----------------------------------------------------------------------===//
179 // This pass reassociates commutative expressions in an order that is designed
180 // to promote better constant propagation, GCSE, LICM, PRE...
182 // For example: 4 + (x + 5) -> x + (4 + 5)
184 FunctionPass *createReassociatePass();
186 //===----------------------------------------------------------------------===//
188 // This pass eliminates correlated conditions, such as these:
190 // if (X > 2) ; // Known false
194 Pass *createCorrelatedExpressionEliminationPass();
196 //===----------------------------------------------------------------------===//
198 // TailDuplication - Eliminate unconditional branches through controlled code
199 // duplication, creating simpler CFG structures.
201 Pass *createTailDuplicationPass();
204 //===----------------------------------------------------------------------===//
206 // CFG Simplification - Merge basic blocks, eliminate unreachable blocks,
207 // simplify terminator instructions, etc...
209 FunctionPass *createCFGSimplificationPass();
212 //===----------------------------------------------------------------------===//
214 // BreakCriticalEdges pass - Break all of the critical edges in the CFG by
215 // inserting a dummy basic block. This pass may be "required" by passes that
216 // cannot deal with critical edges. For this usage, a pass must call:
218 // AU.addRequiredID(BreakCriticalEdgesID);
220 // This pass obviously invalidates the CFG, but can update forward dominator
221 // (set, immediate dominators, tree, and frontier) information.
223 Pass *createBreakCriticalEdgesPass();
224 extern const PassInfo *BreakCriticalEdgesID;
226 //===----------------------------------------------------------------------===//
228 // LoopSimplify pass - Insert Pre-header blocks into the CFG for every function
229 // in the module. This pass updates dominator information, loop information,
230 // and does not add critical edges to the CFG.
232 // AU.addRequiredID(LoopSimplifyID);
234 Pass *createLoopSimplifyPass();
235 extern const PassInfo *LoopSimplifyID;
237 //===----------------------------------------------------------------------===//
239 // This pass eliminates call instructions to the current function which occur
240 // immediately before return instructions.
242 FunctionPass *createTailCallEliminationPass();
245 //===----------------------------------------------------------------------===//
246 // This pass convert malloc and free instructions to %malloc & %free function
249 FunctionPass *createLowerAllocationsPass();
251 //===----------------------------------------------------------------------===//
252 // This pass converts SwitchInst instructions into a sequence of chained binary
253 // branch instructions.
255 FunctionPass *createLowerSwitchPass();
257 //===----------------------------------------------------------------------===//
258 // This pass converts SelectInst instructions into conditional branch and PHI
259 // instructions. If the OnlyFP flag is set to true, then only floating point
260 // select instructions are lowered.
262 FunctionPass *createLowerSelectPass(bool OnlyFP = false);
264 //===----------------------------------------------------------------------===//
265 // This pass converts invoke and unwind instructions to use sjlj exception
266 // handling mechanisms. Note that after this pass runs the CFG is not entirely
267 // accurate (exceptional control flow edges are not correct anymore) so only
268 // very simple things should be done after the lowerinvoke pass has run (like
269 // generation of native code). This should not be used as a general purpose "my
270 // LLVM-to-LLVM pass doesn't support the invoke instruction yet" lowering pass.
272 FunctionPass *createLowerInvokePass();
273 extern const PassInfo *LowerInvokePassID;
275 //===----------------------------------------------------------------------===//
277 // These functions removes symbols from functions and modules.
279 Pass *createSymbolStrippingPass();
280 Pass *createFullSymbolStrippingPass();
282 } // End llvm namespace