6502/llvm-6502
1
0
Fork 0
mirror of https://github.com/c64scene-ar/llvm-6502.git synced 2024-12-14 11:32:34 +00:00
Code Issues Projects Releases Wiki Activity

Generalize some of the add tests to allow for reassociation to take place

Browse Source 
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@7825 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2003-08-13 19:01:45 +00:00
parent d2ae23979c
commit 564a727969
1 changed files with 130 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

140
lib/Transforms/Scalar/InstructionCombining.cpp
View File

@ -267,18 +267,140 @@ static unsigned Log2(uint64_t Val) {
return Count;
}
/// AssociativeOpt - Perform an optimization on an associative operator. This
/// function is designed to check a chain of associative operators for a
/// potential to apply a certain optimization. Since the optimization may be
/// applicable if the expression was reassociated, this checks the chain, then
/// reassociates the expression as necessary to expose the optimization
/// opportunity. This makes use of a special Functor, which must define
/// 'shouldApply' and 'apply' methods.
///
template<typename Functor>
Instruction *AssociativeOpt(BinaryOperator &Root, const Functor &F) {
unsigned Opcode = Root.getOpcode();
Value *LHS = Root.getOperand(0);
// Quick check, see if the immediate LHS matches...
if (F.shouldApply(LHS))
return F.apply(Root);
// Otherwise, if the LHS is not of the same opcode as the root, return.
Instruction *LHSI = dyn_cast<Instruction>(LHS);
while (LHSI && LHSI->getOpcode() == Opcode && LHSI->use_size() == 1) {
// Should we apply this transform to the RHS?
bool ShouldApply = F.shouldApply(LHSI->getOperand(1));
// If not to the RHS, check to see if we should apply to the LHS...
if (!ShouldApply && F.shouldApply(LHSI->getOperand(0))) {
cast<BinaryOperator>(LHSI)->swapOperands(); // Make the LHS the RHS
ShouldApply = true;
}
// If the functor wants to apply the optimization to the RHS of LHSI,
// reassociate the expression from ((? op A) op B) to (? op (A op B))
if (ShouldApply) {
BasicBlock *BB = Root.getParent();
// All of the instructions have a single use and have no side-effects,
// because of this, we can pull them all into the current basic block.
if (LHSI->getParent() != BB) {
// Move all of the instructions from root to LHSI into the current
// block.
Instruction *TmpLHSI = cast<Instruction>(Root.getOperand(0));
Instruction *LastUse = &Root;
while (TmpLHSI->getParent() == BB) {
LastUse = TmpLHSI;
TmpLHSI = cast<Instruction>(TmpLHSI->getOperand(0));
}
// Loop over all of the instructions in other blocks, moving them into
// the current one.
Value *TmpLHS = TmpLHSI;
do {
TmpLHSI = cast<Instruction>(TmpLHS);
// Remove from current block...
TmpLHSI->getParent()->getInstList().remove(TmpLHSI);
// Insert before the last instruction...
BB->getInstList().insert(LastUse, TmpLHSI);
TmpLHS = TmpLHSI->getOperand(0);
} while (TmpLHSI != LHSI);
}
// Now all of the instructions are in the current basic block, go ahead
// and perform the reassociation.
Instruction *TmpLHSI = cast<Instruction>(Root.getOperand(0));
// First move the selected RHS to the LHS of the root...
Root.setOperand(0, LHSI->getOperand(1));
// Make what used to be the LHS of the root be the user of the root...
Value *ExtraOperand = TmpLHSI->getOperand(1);
Root.replaceAllUsesWith(TmpLHSI); // Users now use TmpLHSI
TmpLHSI->setOperand(1, &Root); // TmpLHSI now uses the root
BB->getInstList().remove(&Root); // Remove root from the BB
BB->getInstList().insert(TmpLHSI, &Root); // Insert root before TmpLHSI
// Now propagate the ExtraOperand down the chain of instructions until we
// get to LHSI.
while (TmpLHSI != LHSI) {
Instruction *NextLHSI = cast<Instruction>(TmpLHSI->getOperand(0));
Value *NextOp = NextLHSI->getOperand(1);
NextLHSI->setOperand(1, ExtraOperand);
TmpLHSI = NextLHSI;
ExtraOperand = NextOp;
}
// Now that the instructions are reassociated, have the functor perform
// the transformation...
return F.apply(Root);
}
LHSI = dyn_cast<Instruction>(LHSI->getOperand(0));
}
return 0;
}
// AddRHS - Implements: X + X --> X << 1
struct AddRHS {
Value *RHS;
AddRHS(Value *rhs) : RHS(rhs) {}
bool shouldApply(Value *LHS) const { return LHS == RHS; }
Instruction *apply(BinaryOperator &Add) const {
return new ShiftInst(Instruction::Shl, Add.getOperand(0),
ConstantInt::get(Type::UByteTy, 1));
}
};
// AddMaskingAnd - Implements (A & C1)+(B & C2) --> (A & C1)|(B & C2)
// iff C1&C2 == 0
struct AddMaskingAnd {
Constant *C2;
AddMaskingAnd(Constant *c) : C2(c) {}
bool shouldApply(Value *LHS) const {
if (Constant *C1 = dyn_castMaskingAnd(LHS))
return ConstantExpr::get(Instruction::And, C1, C2)->isNullValue();
return false;
}
Instruction *apply(BinaryOperator &Add) const {
return BinaryOperator::create(Instruction::Or, Add.getOperand(0),
Add.getOperand(1));
}
};
Instruction *InstCombiner::visitAdd(BinaryOperator &I) {
bool Changed = SimplifyCommutative(I);
Value *LHS = I.getOperand(0), *RHS = I.getOperand(1);
// Eliminate 'add int %X, 0'
// X + 0 --> X
if (RHS == Constant::getNullValue(I.getType()))
return ReplaceInstUsesWith(I, LHS);
// Convert 'add X, X' to 'shl X, 1'
if (LHS == RHS && I.getType()->isInteger())
return new ShiftInst(Instruction::Shl, LHS,
ConstantInt::get(Type::UByteTy, 1));
// X + X --> X << 1
if (I.getType()->isInteger())
if (Instruction *Result = AssociativeOpt(I, AddRHS(RHS))) return Result;
// -A + B --> B - A
if (Value *V = dyn_castNegVal(LHS))
@ -307,11 +429,9 @@ Instruction *InstCombiner::visitAdd(BinaryOperator &I) {
return BinaryOperator::create(Instruction::Mul, LHS, CP1);
}
// (A & C1)+(B & C2) -> (A & C1)|(B & C2) iff C1&C2 == 0
if (Constant *C1 = dyn_castMaskingAnd(LHS))
if (Constant *C2 = dyn_castMaskingAnd(RHS))
if (ConstantExpr::get(Instruction::And, C1, C2)->isNullValue())
return BinaryOperator::create(Instruction::Or, LHS, RHS);
// (A & C1)+(B & C2) --> (A & C1)|(B & C2) iff C1&C2 == 0
if (Constant *C2 = dyn_castMaskingAnd(RHS))
if (Instruction *R = AssociativeOpt(I, AddMaskingAnd(C2))) return R;
return Changed ? &I : 0;
}