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Add instruction combining for ((A&~B)|(~A&B)) -> A^B and all permutations.

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llvm-svn: 60291
This commit is contained in:
Bill Wendling 2008-11-30 13:52:49 +00:00
parent 3e27ac16a6
commit 66a7442059
3 changed files with 65 additions and 6 deletions
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6
lib/Target/README.txt
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@ -1171,12 +1171,6 @@ Should combine to "a | 1". Currently not optimized with "clang
//===---------------------------------------------------------------------===//
int a(int a, int b, int c) {return ((a&~b) | (~a&b));}
Should fold to xor. Currently not optimized with "clang -emit-llvm-bc
| opt -std-compile-opts".
//===---------------------------------------------------------------------===//
int a(int a, int b, int c) {return (~a & c) | ((c|a) & b);}
Should fold to "(~a & c) | (a & b)". Currently not optimized with
"clang -emit-llvm-bc | opt -std-compile-opts".

23
lib/Transforms/Scalar/InstructionCombining.cpp
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@ -4638,6 +4638,29 @@ Instruction *InstCombiner::visitOr(BinaryOperator &I) {
return Match;
if (Instruction *Match = MatchSelectFromAndOr(D, A, B, C))
return Match;
V1 = V2 = 0;
// ((A&~B)|(~A&B)) -> A^B
if ((match(C, m_Not(m_Value(V1))) &&
match(B, m_Not(m_Value(V2)))))
if (V1 == D && V2 == A)
return BinaryOperator::CreateXor(V1, V2);
// ((~B&A)|(~A&B)) -> A^B
if ((match(A, m_Not(m_Value(V1))) &&
match(B, m_Not(m_Value(V2)))))
if (V1 == D && V2 == C)
return BinaryOperator::CreateXor(V1, V2);
// ((A&~B)|(B&~A)) -> A^B
if ((match(C, m_Not(m_Value(V1))) &&
match(D, m_Not(m_Value(V2)))))
if (V1 == B && V2 == A)
return BinaryOperator::CreateXor(V1, V2);
// ((~B&A)|(B&~A)) -> A^B
if ((match(A, m_Not(m_Value(V1))) &&
match(D, m_Not(m_Value(V2)))))
if (V1 == B && V2 == C)
return BinaryOperator::CreateXor(V1, V2);
}
// (X >> Z) | (Y >> Z) -> (X|Y) >> Z for all shifts.

42
test/Transforms/InstCombine/or-to-xor.ll Normal file
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@ -0,0 +1,42 @@
; RUN: llvm-as < %s | opt -instcombine | llvm-dis | grep {xor i32 %b, %a} | count 4
; RUN: llvm-as < %s | opt -instcombine | llvm-dis | not grep {and}
define i32 @func1(i32 %a, i32 %b) nounwind readnone {
entry:
%b_not = xor i32 %b, -1
%0 = and i32 %a, %b_not
%a_not = xor i32 %a, -1
%1 = and i32 %a_not, %b
%2 = or i32 %0, %1
ret i32 %2
}
define i32 @func2(i32 %a, i32 %b) nounwind readnone {
entry:
%b_not = xor i32 %b, -1
%0 = and i32 %b_not, %a
%a_not = xor i32 %a, -1
%1 = and i32 %a_not, %b
%2 = or i32 %0, %1
ret i32 %2
}
define i32 @func3(i32 %a, i32 %b) nounwind readnone {
entry:
%b_not = xor i32 %b, -1
%0 = and i32 %a, %b_not
%a_not = xor i32 %a, -1
%1 = and i32 %b, %a_not
%2 = or i32 %0, %1
ret i32 %2
}
define i32 @func4(i32 %a, i32 %b) nounwind readnone {
entry:
%b_not = xor i32 %b, -1
%0 = and i32 %b_not, %a
%a_not = xor i32 %a, -1
%1 = and i32 %b, %a_not
%2 = or i32 %0, %1
ret i32 %2
}