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Exploit distributive laws (eg: And distributes over Or, Mul over Add, etc) in a

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fairly systematic way in instcombine.  Some of these cases were already dealt
with, in which case I removed the existing code.  The case of Add has a bunch of
funky logic which covers some of this plus a few variants (considers shifts to be
a form of multiplication), which I didn't touch.  The simplification performed is:
A*B+A*C -> A*(B+C).  The improvement is to do this in cases that were not already
handled [such as A*B-A*C -> A*(B-C), which was reported on the mailing list], and
also to do it more often by not checking for "only one use" if "B+C" simplifies.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@120024 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Duncan Sands
2010-11-23 14:23:47 +00:00
parent 0cc5b1f60e
commit 5057f38141
5 changed files with 144 additions and 42 deletions
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5
lib/Transforms/InstCombine/InstCombineAddSub.cpp
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@@ -91,6 +91,8 @@ Instruction *InstCombiner::visitAdd(BinaryOperator &I) {
I.hasNoUnsignedWrap(), TD))
return ReplaceInstUsesWith(I, V);
if (Instruction *NV = SimplifyDistributed(I)) // (A*B)+(A*C) -> A*(B+C)
return NV;
if (Constant *RHSC = dyn_cast<Constant>(RHS)) {
if (ConstantInt *CI = dyn_cast<ConstantInt>(RHSC)) {
@@ -548,6 +550,9 @@ Instruction *InstCombiner::visitSub(BinaryOperator &I) {
if (Op0 == Op1) // sub X, X -> 0
return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
if (Instruction *NV = SimplifyDistributed(I)) // (A*B)-(A*C) -> A*(B-C)
return NV;
// If this is a 'B = x-(-A)', change to B = x+A. This preserves NSW/NUW.
if (Value *V = dyn_castNegVal(Op1)) {
BinaryOperator *Res = BinaryOperator::CreateAdd(Op0, V);