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be more aggressive about transforming add -> or when the operands have no

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intersecting bits.  This triggers all over the place, for example in lencode,
with adds of stuff like:

	%tmp580 = mul i32 %tmp579, 2	
	%tmp582 = and i32 %b8, 1
and

	%tmp28 = shl i32 %abs.i, 1		
	%sign.0 = select i1 %tmp23, i32 1, i32 0
and
	%tmp344 = shl i32 %tmp343, 2	
	%tmp346 = and i32 %tmp96, 3

etc.

llvm-svn: 51263
This commit is contained in:
Chris Lattner 2008-05-19 20:01:56 +00:00
parent 1c11cba7ec
commit 510a6b249c
2 changed files with 34 additions and 0 deletions
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19
lib/Transforms/Scalar/InstructionCombining.cpp
View File

@ -2503,6 +2503,25 @@ Instruction *InstCombiner::visitAdd(BinaryOperator &I) {
if (match(RHS, m_And(m_Value(), m_ConstantInt(C2))))
if (Instruction *R = AssociativeOpt(I, AddMaskingAnd(C2)))
return R;
// A+B --> A|B iff A and B have no bits set in common.
if (const IntegerType *IT = dyn_cast<IntegerType>(I.getType())) {
APInt Mask = APInt::getAllOnesValue(IT->getBitWidth());
APInt LHSKnownOne(IT->getBitWidth(), 0);
APInt LHSKnownZero(IT->getBitWidth(), 0);
ComputeMaskedBits(LHS, Mask, LHSKnownZero, LHSKnownOne);
if (LHSKnownZero != 0) {
APInt RHSKnownOne(IT->getBitWidth(), 0);
APInt RHSKnownZero(IT->getBitWidth(), 0);
ComputeMaskedBits(RHS, Mask, RHSKnownZero, RHSKnownOne);
// No bits in common -> bitwise or.
if ((LHSKnownZero|RHSKnownZero).isAllOnesValue()) {
cerr << "HACK\n" << *LHS << *RHS << "\n";
return BinaryOperator::CreateOr(LHS, RHS);
}
}
}
// W*X + Y*Z --> W * (X+Z) iff W == Y
if (I.getType()->isIntOrIntVector()) {

15
test/Transforms/InstCombine/add2.ll
View File

@ -29,3 +29,18 @@ EntryBlock:
declare i32 @callee(i32)
define i32 @test3(i32 %A) {
%B = and i32 %A, 7
%C = and i32 %A, 32
%F = add i32 %B, %C
ret i32 %F
}
define i32 @test4(i32 %A) {
%B = and i32 %A, 128
%C = lshr i32 %A, 30
%F = add i32 %B, %C
ret i32 %F
}