1 //===-- Scalar.h - Scalar Transformations ------------------------*- C++ -*-==//
3 // This header file defines prototypes for accessor functions that expose passes
4 // in the Scalar transformations library.
6 //===----------------------------------------------------------------------===//
8 #ifndef LLVM_TRANSFORMS_SCALAR_H
9 #define LLVM_TRANSFORMS_SCALAR_H
12 class GetElementPtrInst;
15 //===----------------------------------------------------------------------===//
17 // Constant Propogation Pass - A worklist driven constant propogation pass
19 Pass *createConstantPropogationPass();
22 //===----------------------------------------------------------------------===//
24 // Sparse Conditional Constant Propogation Pass
26 Pass *createSCCPPass();
29 //===----------------------------------------------------------------------===//
31 // DeadInstElimination - This pass quickly removes trivially dead instructions
32 // without modifying the CFG of the function. It is a BasicBlockPass, so it
33 // runs efficiently when queued next to other BasicBlockPass's.
35 Pass *createDeadInstEliminationPass();
38 //===----------------------------------------------------------------------===//
40 // DeadCodeElimination - This pass is more powerful than DeadInstElimination,
41 // because it is worklist driven that can potentially revisit instructions when
42 // their other instructions become dead, to eliminate chains of dead
45 Pass *createDeadCodeEliminationPass();
48 //===----------------------------------------------------------------------===//
50 // AggressiveDCE - This pass uses the SSA based Aggressive DCE algorithm. This
51 // algorithm assumes instructions are dead until proven otherwise, which makes
52 // it more successful are removing non-obviously dead instructions.
54 Pass *createAggressiveDCEPass();
57 //===----------------------------------------------------------------------===//
59 // DecomposeMultiDimRefs - Convert multi-dimensional references consisting of
60 // any combination of 2 or more array and structure indices into a sequence of
61 // instructions (using getelementpr and cast) so that each instruction has at
62 // most one index (except structure references, which need an extra leading
65 // This pass decomposes all multi-dimensional references in a function.
66 Pass *createDecomposeMultiDimRefsPass();
68 // This function decomposes a single instance of such a reference.
69 // Return value: true if the instruction was replaced; false otherwise.
71 bool DecomposeArrayRef(GetElementPtrInst* GEP);
73 //===----------------------------------------------------------------------===//
75 // GCSE - This pass is designed to be a very quick global transformation that
76 // eliminates global common subexpressions from a function. It does this by
77 // examining the SSA value graph of the function, instead of doing slow
78 // bit-vector computations.
80 Pass *createGCSEPass();
83 //===----------------------------------------------------------------------===//
85 // InductionVariableSimplify - Transform induction variables in a program to all
86 // use a single cannonical induction variable per loop.
88 Pass *createIndVarSimplifyPass();
91 //===----------------------------------------------------------------------===//
93 // InstructionCombining - Combine instructions to form fewer, simple
94 // instructions. This pass does not modify the CFG, and has a tendancy to
95 // make instructions dead, so a subsequent DCE pass is useful.
97 // This pass combines things like:
101 // %Z = add int 2, %X
103 Pass *createInstructionCombiningPass();
106 //===----------------------------------------------------------------------===//
108 // LICM - This pass is a simple natural loop based loop invariant code motion
111 Pass *createLICMPass();
114 //===----------------------------------------------------------------------===//
116 // PiNodeInsertion - This pass inserts single entry Phi nodes into basic blocks
117 // that are preceeded by a conditional branch, where the branch gives
118 // information about the operands of the condition. For example, this C code:
119 // if (x == 0) { ... = x + 4;
122 // x2 = phi(x); // Node that can hold data flow information about X
125 // Since the direction of the condition branch gives information about X itself
126 // (whether or not it is zero), some passes (like value numbering or ABCD) can
127 // use the inserted Phi/Pi nodes as a place to attach information, in this case
128 // saying that X has a value of 0 in this scope. The power of this analysis
129 // information is that "in the scope" translates to "for all uses of x2".
131 // This special form of Phi node is refered to as a Pi node, following the
132 // terminology defined in the "Array Bounds Checks on Demand" paper.
134 Pass *createPiNodeInsertionPass();
137 //===----------------------------------------------------------------------===//
139 // This pass is used to promote memory references to be register references. A
140 // simple example of the transformation performed by this pass is:
143 // %X = alloca int, uint 1 ret int 42
144 // store int 42, int *%X
148 Pass *createPromoteMemoryToRegister();
151 //===----------------------------------------------------------------------===//
153 // This pass reassociates commutative expressions in an order that is designed
154 // to promote better constant propogation, GCSE, LICM, PRE...
156 // For example: 4 + (x + 5) -> x + (4 + 5)
158 Pass *createReassociatePass();
160 //===----------------------------------------------------------------------===//
162 // This pass eliminates correlated conditions, such as these:
164 // if (X > 2) ; // Known false
168 Pass *createCorrelatedExpressionEliminationPass();
170 //===----------------------------------------------------------------------===//
172 // CFG Simplification - Merge basic blocks, eliminate unreachable blocks,
173 // simplify terminator instructions, etc...
175 Pass *createCFGSimplificationPass();
177 //===----------------------------------------------------------------------===//
179 // BreakCriticalEdges pass - Break all of the critical edges in the CFG by
180 // inserting a dummy basic block. This pass may be "required" by passes that
181 // cannot deal with critical edges. For this usage, a pass must call:
183 // AU.addRequiredID(BreakCriticalEdgesID);
185 // This pass obviously invalidates the CFG, but can update forward dominator
186 // (set, immediate dominators, and tree) information.
188 Pass *createBreakCriticalEdgesPass();
189 extern const PassInfo *BreakCriticalEdgesID;
191 //===----------------------------------------------------------------------===//
192 // These two passes convert malloc and free instructions to and from %malloc &
193 // %free function calls.
195 Pass *createLowerAllocationsPass();
196 Pass *createRaiseAllocationsPass();
199 //===----------------------------------------------------------------------===//
201 // These functions removes symbols from functions and modules.
203 Pass *createSymbolStrippingPass();
204 Pass *createFullSymbolStrippingPass();