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[InstCombine] don't form select from logic ops if it's unlikely that we'll eliminate any ops 

llvm-svn: 274926
This commit is contained in:
Sanjay Patel 2016-07-08 20:53:29 +00:00
parent 297a0e67b6
commit f4a08ede03
2 changed files with 23 additions and 20 deletions
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39
llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
View File

@ -2222,23 +2222,28 @@ Instruction *InstCombiner::visitOr(BinaryOperator &I) {
}
}
// (Cond & C) | (~Cond & D) -> Cond ? C : D, and commuted variants.
if (Value *V = matchSelectFromAndOr(A, C, B, D, *Builder))
return replaceInstUsesWith(I, V);
if (Value *V = matchSelectFromAndOr(A, C, D, B, *Builder))
return replaceInstUsesWith(I, V);
if (Value *V = matchSelectFromAndOr(C, A, B, D, *Builder))
return replaceInstUsesWith(I, V);
if (Value *V = matchSelectFromAndOr(C, A, D, B, *Builder))
return replaceInstUsesWith(I, V);
if (Value *V = matchSelectFromAndOr(B, D, A, C, *Builder))
return replaceInstUsesWith(I, V);
if (Value *V = matchSelectFromAndOr(B, D, C, A, *Builder))
return replaceInstUsesWith(I, V);
if (Value *V = matchSelectFromAndOr(D, B, A, C, *Builder))
return replaceInstUsesWith(I, V);
if (Value *V = matchSelectFromAndOr(D, B, C, A, *Builder))
return replaceInstUsesWith(I, V);
// Don't try to form a select if it's unlikely that we'll get rid of at
// least one of the operands. A select is generally more expensive than the
// 'or' that it is replacing.
if (Op0->hasOneUse() || Op1->hasOneUse()) {
// (Cond & C) | (~Cond & D) -> Cond ? C : D, and commuted variants.
if (Value *V = matchSelectFromAndOr(A, C, B, D, *Builder))
return replaceInstUsesWith(I, V);
if (Value *V = matchSelectFromAndOr(A, C, D, B, *Builder))
return replaceInstUsesWith(I, V);
if (Value *V = matchSelectFromAndOr(C, A, B, D, *Builder))
return replaceInstUsesWith(I, V);
if (Value *V = matchSelectFromAndOr(C, A, D, B, *Builder))
return replaceInstUsesWith(I, V);
if (Value *V = matchSelectFromAndOr(B, D, A, C, *Builder))
return replaceInstUsesWith(I, V);
if (Value *V = matchSelectFromAndOr(B, D, C, A, *Builder))
return replaceInstUsesWith(I, V);
if (Value *V = matchSelectFromAndOr(D, B, A, C, *Builder))
return replaceInstUsesWith(I, V);
if (Value *V = matchSelectFromAndOr(D, B, C, A, *Builder))
return replaceInstUsesWith(I, V);
}
// ((A&~B)|(~A&B)) -> A^B
if ((match(C, m_Not(m_Specific(D))) &&

4
llvm/test/Transforms/InstCombine/logical-select.ll
View File

@ -300,10 +300,8 @@ define i1 @bools_multi_uses2(i1 %a, i1 %b, i1 %c) {
; CHECK-NEXT: [[NOT:%.*]] = xor i1 %c, true
; CHECK-NEXT: [[AND1:%.*]] = and i1 [[NOT]], %a
; CHECK-NEXT: [[AND2:%.*]] = and i1 %c, %b
; CHECK-NEXT: [[TMP1:%.*]] = select i1 %c, i1 %b, i1 %a
; CHECK-NEXT: [[ADD:%.*]] = xor i1 [[AND1]], [[AND2]]
; CHECK-NEXT: [[AND3:%.*]] = and i1 [[TMP1]], [[ADD]]
; CHECK-NEXT: ret i1 [[AND3]]
; CHECK-NEXT: ret i1 [[ADD]]
;
%not = xor i1 %c, -1
%and1 = and i1 %not, %a