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4b35f83b91
when one of them can be converted to a trivial icmp and conditional branch. This addresses what is essentially a phase ordering problem. SimplifyCFG knows how to do this transformation, but it doesn't do so if the primary block has any instructions in it other than an icmp and a branch. In the given testcase, the block contains other instructions, however they are loop-invariant and can be hoisted. SimplifyCFG doesn't have LoopInfo though, so it can't hoist them. And, it's important that the blocks be merged before LoopRotation, as it doesn't support multiple-exit loops. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@74396 91177308-0d34-0410-b5e6-96231b3b80d8
127 lines
5.0 KiB
C++
127 lines
5.0 KiB
C++
//===-- Local.h - Functions to perform local transformations ----*- C++ -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This family of functions perform various local transformations to the
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// program.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_TRANSFORMS_UTILS_LOCAL_H
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#define LLVM_TRANSFORMS_UTILS_LOCAL_H
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namespace llvm {
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class User;
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class BasicBlock;
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class BranchInst;
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class Instruction;
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class Value;
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class Pass;
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class PHINode;
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class AllocaInst;
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class ConstantExpr;
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class TargetData;
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struct DbgInfoIntrinsic;
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template<typename T> class SmallVectorImpl;
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//===----------------------------------------------------------------------===//
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// Local analysis.
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//
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/// isSafeToLoadUnconditionally - Return true if we know that executing a load
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/// from this value cannot trap. If it is not obviously safe to load from the
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/// specified pointer, we do a quick local scan of the basic block containing
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/// ScanFrom, to determine if the address is already accessed.
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bool isSafeToLoadUnconditionally(Value *V, Instruction *ScanFrom);
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//===----------------------------------------------------------------------===//
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// Local constant propagation.
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//
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/// ConstantFoldTerminator - If a terminator instruction is predicated on a
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/// constant value, convert it into an unconditional branch to the constant
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/// destination. This is a nontrivial operation because the successors of this
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/// basic block must have their PHI nodes updated.
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///
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bool ConstantFoldTerminator(BasicBlock *BB);
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//===----------------------------------------------------------------------===//
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// Local dead code elimination.
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//
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/// isInstructionTriviallyDead - Return true if the result produced by the
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/// instruction is not used, and the instruction has no side effects.
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///
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bool isInstructionTriviallyDead(Instruction *I);
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/// RecursivelyDeleteTriviallyDeadInstructions - If the specified value is a
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/// trivially dead instruction, delete it. If that makes any of its operands
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/// trivially dead, delete them too, recursively.
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void RecursivelyDeleteTriviallyDeadInstructions(Value *V);
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/// RecursivelyDeleteDeadPHINode - If the specified value is an effectively
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/// dead PHI node, due to being a def-use chain of single-use nodes that
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/// either forms a cycle or is terminated by a trivially dead instruction,
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/// delete it. If that makes any of its operands trivially dead, delete them
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/// too, recursively.
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void RecursivelyDeleteDeadPHINode(PHINode *PN);
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//===----------------------------------------------------------------------===//
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// Control Flow Graph Restructuring.
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//
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/// MergeBasicBlockIntoOnlyPred - BB is a block with one predecessor and its
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/// predecessor is known to have one successor (BB!). Eliminate the edge
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/// between them, moving the instructions in the predecessor into BB. This
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/// deletes the predecessor block.
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///
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void MergeBasicBlockIntoOnlyPred(BasicBlock *BB);
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/// SimplifyCFG - This function is used to do simplification of a CFG. For
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/// example, it adjusts branches to branches to eliminate the extra hop, it
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/// eliminates unreachable basic blocks, and does other "peephole" optimization
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/// of the CFG. It returns true if a modification was made, possibly deleting
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/// the basic block that was pointed to.
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///
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/// WARNING: The entry node of a method may not be simplified.
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///
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bool SimplifyCFG(BasicBlock *BB);
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/// FoldBranchToCommonDest - If this basic block is ONLY a setcc and a branch,
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/// and if a predecessor branches to us and one of our successors, fold the
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/// setcc into the predecessor and use logical operations to pick the right
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/// destination.
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bool FoldBranchToCommonDest(BranchInst *BI);
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/// DemoteRegToStack - This function takes a virtual register computed by an
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/// Instruction and replaces it with a slot in the stack frame, allocated via
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/// alloca. This allows the CFG to be changed around without fear of
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/// invalidating the SSA information for the value. It returns the pointer to
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/// the alloca inserted to create a stack slot for X.
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///
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AllocaInst *DemoteRegToStack(Instruction &X, bool VolatileLoads = false,
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Instruction *AllocaPoint = 0);
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/// DemotePHIToStack - This function takes a virtual register computed by a phi
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/// node and replaces it with a slot in the stack frame, allocated via alloca.
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/// The phi node is deleted and it returns the pointer to the alloca inserted.
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AllocaInst *DemotePHIToStack(PHINode *P, Instruction *AllocaPoint = 0);
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/// OnlyUsedByDbgIntrinsics - Return true if the instruction I is only used
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/// by DbgIntrinsics. If DbgInUses is specified then the vector is filled
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/// with DbgInfoIntrinsic that use the instruction I.
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bool OnlyUsedByDbgInfoIntrinsics(Instruction *I,
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SmallVectorImpl<DbgInfoIntrinsic *> *DbgInUses = 0);
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} // End llvm namespace
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#endif
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