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move some generally useful functions out of jump threading 

into libanalysis and transformutils.

llvm-svn: 86735
This commit is contained in:
Chris Lattner 2009-11-10 22:26:15 +00:00
parent 42855f2043
commit 852d6d64ff
5 changed files with 106 additions and 85 deletions
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9
llvm/include/llvm/Analysis/InstructionSimplify.h
View File

@ -59,6 +59,15 @@ namespace llvm {
/// instruction. If not, this returns null.
Value *SimplifyInstruction(Instruction *I, const TargetData *TD = 0);
/// ReplaceAndSimplifyAllUses - Perform From->replaceAllUsesWith(To) and then
/// delete the From instruction. In addition to a basic RAUW, this does a
/// recursive simplification of the updated instructions. This catches
/// things where one simplification exposes other opportunities. This only
/// simplifies and deletes scalar operations, it does not change the CFG.
///
void ReplaceAndSimplifyAllUses(Instruction *From, Value *To,
const TargetData *TD = 0);
} // end namespace llvm
#endif

15
llvm/include/llvm/Transforms/Utils/Local.h
View File

@ -78,6 +78,21 @@ void RecursivelyDeleteDeadPHINode(PHINode *PN);
// Control Flow Graph Restructuring.
//
/// RemovePredecessorAndSimplify - Like BasicBlock::removePredecessor, this
/// method is called when we're about to delete Pred as a predecessor of BB. If
/// BB contains any PHI nodes, this drops the entries in the PHI nodes for Pred.
///
/// Unlike the removePredecessor method, this attempts to simplify uses of PHI
/// nodes that collapse into identity values. For example, if we have:
/// x = phi(1, 0, 0, 0)
/// y = and x, z
///
/// .. and delete the predecessor corresponding to the '1', this will attempt to
/// recursively fold the 'and' to 0.
void RemovePredecessorAndSimplify(BasicBlock *BB, BasicBlock *Pred,
TargetData *TD = 0);
/// MergeBasicBlockIntoOnlyPred - BB is a block with one predecessor and its
/// predecessor is known to have one successor (BB!). Eliminate the edge
/// between them, moving the instructions in the predecessor into BB. This

35
llvm/lib/Analysis/InstructionSimplify.cpp
View File

@ -15,6 +15,7 @@
#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/Analysis/ConstantFolding.h"
#include "llvm/Support/ValueHandle.h"
#include "llvm/Instructions.h"
#include "llvm/Support/PatternMatch.h"
using namespace llvm;
@ -311,3 +312,37 @@ Value *llvm::SimplifyInstruction(Instruction *I, const TargetData *TD) {
}
}
/// ReplaceAndSimplifyAllUses - Perform From->replaceAllUsesWith(To) and then
/// delete the From instruction. In addition to a basic RAUW, this does a
/// recursive simplification of the newly formed instructions. This catches
/// things where one simplification exposes other opportunities. This only
/// simplifies and deletes scalar operations, it does not change the CFG.
///
void llvm::ReplaceAndSimplifyAllUses(Instruction *From, Value *To,
const TargetData *TD) {
assert(From != To && "ReplaceAndSimplifyAllUses(X,X) is not valid!");
// FromHandle - This keeps a weakvh on the from value so that we can know if
// it gets deleted out from under us in a recursive simplification.
WeakVH FromHandle(From);
while (!From->use_empty()) {
// Update the instruction to use the new value.
Use &U = From->use_begin().getUse();
Instruction *User = cast<Instruction>(U.getUser());
U = To;
// See if we can simplify it.
if (Value *V = SimplifyInstruction(User, TD)) {
// Recursively simplify this.
ReplaceAndSimplifyAllUses(User, V, TD);
// If the recursive simplification ended up revisiting and deleting 'From'
// then we're done.
if (FromHandle == 0)
return;
}
}
From->eraseFromParent();
}

83
llvm/lib/Transforms/Scalar/JumpThreading.cpp
View File

@ -203,89 +203,6 @@ static unsigned getJumpThreadDuplicationCost(const BasicBlock *BB) {
return Size;
}
//===----------------------------------------------------------------------===//
/// ReplaceAndSimplifyAllUses - Perform From->replaceAllUsesWith(To) and then
/// delete the From instruction. In addition to a basic RAUW, this does a
/// recursive simplification of the newly formed instructions. This catches
/// things where one simplification exposes other opportunities. This only
/// simplifies and deletes scalar operations, it does not change the CFG.
///
static void ReplaceAndSimplifyAllUses(Instruction *From, Value *To,
const TargetData *TD) {
assert(From != To && "ReplaceAndSimplifyAllUses(X,X) is not valid!");
// FromHandle - This keeps a weakvh on the from value so that we can know if
// it gets deleted out from under us in a recursive simplification.
WeakVH FromHandle(From);
while (!From->use_empty()) {
// Update the instruction to use the new value.
Use &U = From->use_begin().getUse();
Instruction *User = cast<Instruction>(U.getUser());
U = To;
// See if we can simplify it.
if (Value *V = SimplifyInstruction(User, TD)) {
// Recursively simplify this.
ReplaceAndSimplifyAllUses(User, V, TD);
// If the recursive simplification ended up revisiting and deleting 'From'
// then we're done.
if (FromHandle == 0)
return;
}
}
From->eraseFromParent();
}
/// RemovePredecessorAndSimplify - Like BasicBlock::removePredecessor, this
/// method is called when we're about to delete Pred as a predecessor of BB. If
/// BB contains any PHI nodes, this drops the entries in the PHI nodes for Pred.
///
/// Unlike the removePredecessor method, this attempts to simplify uses of PHI
/// nodes that collapse into identity values. For example, if we have:
/// x = phi(1, 0, 0, 0)
/// y = and x, z
///
/// .. and delete the predecessor corresponding to the '1', this will attempt to
/// recursively fold the and to 0.
static void RemovePredecessorAndSimplify(BasicBlock *BB, BasicBlock *Pred,
TargetData *TD) {
// This only adjusts blocks with PHI nodes.
if (!isa<PHINode>(BB->begin()))
return;
// Remove the entries for Pred from the PHI nodes in BB, but do not simplify
// them down. This will leave us with single entry phi nodes and other phis
// that can be removed.
BB->removePredecessor(Pred, true);
WeakVH PhiIt = &BB->front();
while (PHINode *PN = dyn_cast<PHINode>(PhiIt)) {
PhiIt = &*++BasicBlock::iterator(cast<Instruction>(PhiIt));
Value *PNV = PN->hasConstantValue();
if (PNV == 0) continue;
// If we're able to simplify the phi to a single value, substitute the new
// value into all of its uses.
assert(PNV != PN && "hasConstantValue broken");
ReplaceAndSimplifyAllUses(PN, PNV, TD);
// If recursive simplification ended up deleting the next PHI node we would
// iterate to, then our iterator is invalid, restart scanning from the top
// of the block.
if (PhiIt == 0) PhiIt = &BB->front();
}
}
//===----------------------------------------------------------------------===//
/// FindLoopHeaders - We do not want jump threading to turn proper loop
/// structures into irreducible loops. Doing this breaks up the loop nesting
/// hierarchy and pessimizes later transformations. To prevent this from

49
llvm/lib/Transforms/Utils/Local.cpp
View File

@ -24,6 +24,7 @@
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/Analysis/ConstantFolding.h"
#include "llvm/Analysis/DebugInfo.h"
#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/Analysis/ProfileInfo.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Support/CFG.h"
@ -239,7 +240,7 @@ bool llvm::ConstantFoldTerminator(BasicBlock *BB) {
//===----------------------------------------------------------------------===//
// Local dead code elimination...
// Local dead code elimination.
//
/// isInstructionTriviallyDead - Return true if the result produced by the
@ -326,9 +327,53 @@ llvm::RecursivelyDeleteDeadPHINode(PHINode *PN) {
}
//===----------------------------------------------------------------------===//
// Control Flow Graph Restructuring...
// Control Flow Graph Restructuring.
//
/// RemovePredecessorAndSimplify - Like BasicBlock::removePredecessor, this
/// method is called when we're about to delete Pred as a predecessor of BB. If
/// BB contains any PHI nodes, this drops the entries in the PHI nodes for Pred.
///
/// Unlike the removePredecessor method, this attempts to simplify uses of PHI
/// nodes that collapse into identity values. For example, if we have:
/// x = phi(1, 0, 0, 0)
/// y = and x, z
///
/// .. and delete the predecessor corresponding to the '1', this will attempt to
/// recursively fold the and to 0.
void llvm::RemovePredecessorAndSimplify(BasicBlock *BB, BasicBlock *Pred,
TargetData *TD) {
// This only adjusts blocks with PHI nodes.
if (!isa<PHINode>(BB->begin()))
return;
// Remove the entries for Pred from the PHI nodes in BB, but do not simplify
// them down. This will leave us with single entry phi nodes and other phis
// that can be removed.
BB->removePredecessor(Pred, true);
WeakVH PhiIt = &BB->front();
while (PHINode *PN = dyn_cast<PHINode>(PhiIt)) {
PhiIt = &*++BasicBlock::iterator(cast<Instruction>(PhiIt));
Value *PNV = PN->hasConstantValue();
if (PNV == 0) continue;
// If we're able to simplify the phi to a single value, substitute the new
// value into all of its uses.
assert(PNV != PN && "hasConstantValue broken");
ReplaceAndSimplifyAllUses(PN, PNV, TD);
// If recursive simplification ended up deleting the next PHI node we would
// iterate to, then our iterator is invalid, restart scanning from the top
// of the block.
if (PhiIt == 0) PhiIt = &BB->front();
}
}
/// MergeBasicBlockIntoOnlyPred - DestBB is a block with one predecessor and its
/// predecessor is known to have one successor (DestBB!). Eliminate the edge
/// between them, moving the instructions in the predecessor into DestBB and