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add one more bitfield optimization, allowing clang to generate

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good code on PR4216:

_test_bitfield:                                             ## @test_bitfield
	orl	$32962, %edi
	movl	$4294941946, %eax
	andq	%rdi, %rax
	ret

instead of:

_test_bitfield:
        movl    $4294941696, %ecx
        movl    %edi, %eax
        orl     $194, %edi
        orl     $32768, %eax
        andq    $250, %rdi
        andq    %rax, %rcx
        movq    %rdi, %rax
        orq     %rcx, %rax
        ret

Evan is looking into the remaining andq+imm -> andl optimization.

llvm-svn: 93147
This commit is contained in:
Chris Lattner 2010-01-11 06:55:24 +00:00
parent 16e36659f5
commit 85a6f02b94
2 changed files with 31 additions and 2 deletions
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17
lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
View File

@ -1544,9 +1544,9 @@ Instruction *InstCombiner::visitOr(BinaryOperator &I) {
}
}
// ((V | N) & C1) | (V & C2) --> (V|N) & (C1|C2)
// iff (C1&C2) == 0 and (N&~C1) == 0
if ((C1->getValue() & C2->getValue()) == 0) {
// ((V | N) & C1) | (V & C2) --> (V|N) & (C1|C2)
// iff (C1&C2) == 0 and (N&~C1) == 0
if (match(A, m_Or(m_Value(V1), m_Value(V2))) &&
((V1 == B && MaskedValueIsZero(V2, ~C1->getValue())) || // (V|N)
(V2 == B && MaskedValueIsZero(V1, ~C1->getValue())))) // (N|V)
@ -1560,6 +1560,19 @@ Instruction *InstCombiner::visitOr(BinaryOperator &I) {
return BinaryOperator::CreateAnd(B,
ConstantInt::get(B->getContext(),
C1->getValue()|C2->getValue()));
// ((V|C3)&C1) | ((V|C4)&C2) --> (V|C3|C4)&(C1|C2)
// iff (C1&C2) == 0 and (C3&~C1) == 0 and (C4&~C2) == 0.
ConstantInt *C3 = 0, *C4 = 0;
if (match(A, m_Or(m_Value(V1), m_ConstantInt(C3))) &&
(C3->getValue() & ~C1->getValue()) == 0 &&
match(B, m_Or(m_Specific(V1), m_ConstantInt(C4))) &&
(C4->getValue() & ~C2->getValue()) == 0) {
V2 = Builder->CreateOr(V1, ConstantExpr::getOr(C3, C4), "bitfield");
return BinaryOperator::CreateAnd(V2,
ConstantInt::get(B->getContext(),
C1->getValue()|C2->getValue()));
}
}
}

16
test/Transforms/InstCombine/or.ll
View File

@ -320,3 +320,19 @@ entry:
; CHECK: %E = and i32 %B, -25350
; CHECK: ret i32 %E
}
; PR4216
define i64 @test31(i64 %A) nounwind readnone ssp noredzone {
%B = or i64 %A, 194
%D = and i64 %B, 250
%C = or i64 %A, 32768
%E = and i64 %C, 4294941696
%F = or i64 %D, %E
ret i64 %F
; CHECK: @test31
; CHECK-NEXT: %bitfield = or i64 %A, 32962
; CHECK-NEXT: %F = and i64 %bitfield, 4294941946
; CHECK-NEXT: ret i64 %F
}