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Turn A % (C << N), where C is 2^k, into A & ((C << N)-1) [urem only].

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Turn A / (C1 << N), where C1 is "1<<C2" into A >> (N+C2) [udiv only].

Tested with: rem.ll:test5, div.ll:test10


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@26003 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2006-02-05 07:54:04 +00:00
parent fee906b482
commit 5f3b0eeddb
1 changed files with 35 additions and 0 deletions
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35
lib/Transforms/Scalar/InstructionCombining.cpp
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@ -1261,6 +1261,25 @@ Instruction *InstCombiner::visitDiv(BinaryOperator &I) {
InsertNewInstBefore(Div, I);
return new CastInst(Div, I.getType());
}
} else {
// Known to be an unsigned division.
if (Instruction *RHSI = dyn_cast<Instruction>(I.getOperand(1))) {
// Turn A / (C1 << N), where C1 is "1<<C2" into A >> (N+C2) [udiv only].
if (RHSI->getOpcode() == Instruction::Shl &&
isa<ConstantUInt>(RHSI->getOperand(0))) {
unsigned C1 = cast<ConstantUInt>(RHSI->getOperand(0))->getRawValue();
if (isPowerOf2_64(C1)) {
unsigned C2 = Log2_64(C1);
Value *Add = RHSI->getOperand(1);
if (C2) {
Constant *C2V = ConstantUInt::get(Add->getType(), C2);
Add = InsertNewInstBefore(BinaryOperator::createAdd(Add, C2V,
"tmp"), I);
}
return new ShiftInst(Instruction::Shr, Op0, Add);
}
}
}
}
return 0;
@ -1352,6 +1371,22 @@ Instruction *InstCombiner::visitRem(BinaryOperator &I) {
if (LHS->equalsInt(0))
return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
if (Instruction *RHSI = dyn_cast<Instruction>(I.getOperand(1))) {
// Turn A % (C << N), where C is 2^k, into A & ((C << N)-1) [urem only].
if (I.getType()->isUnsigned() &&
RHSI->getOpcode() == Instruction::Shl &&
isa<ConstantUInt>(RHSI->getOperand(0))) {
unsigned C1 = cast<ConstantUInt>(RHSI->getOperand(0))->getRawValue();
if (isPowerOf2_64(C1)) {
Constant *N1 = ConstantInt::getAllOnesValue(I.getType());
Value *Add = InsertNewInstBefore(BinaryOperator::createAdd(RHSI, N1,
"tmp"), I);
return BinaryOperator::createAnd(Op0, Add);
}
}
}
return 0;
}