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InstCombine: turn (C1 << A) << C2) into (C1 << C2) << A)

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Fixes PR9809.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@130485 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Benjamin Kramer 2011-04-29 08:15:41 +00:00
parent bb0fff0cb4
commit c2e31c1461
2 changed files with 29 additions and 1 deletions
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9
lib/Transforms/InstCombine/InstCombineShifts.cpp
View File

@ -644,7 +644,14 @@ Instruction *InstCombiner::visitShl(BinaryOperator &I) {
return &I;
}
}
// (C1 << A) << C2) -> (C1 << C2) << A)
Constant *C1, *C2;
Value *A;
if (match(I.getOperand(0), m_OneUse(m_Shl(m_Constant(C1), m_Value(A)))) &&
match(I.getOperand(1), m_Constant(C2)))
return BinaryOperator::CreateShl(ConstantExpr::getShl(C1, C2), A);
return 0;
}

21
test/Transforms/InstCombine/shift.ll
View File

@ -485,3 +485,24 @@ entry:
; CHECK: ret i8 %tmp551
ret i8 %tmp55
}
; PR9809
define i32 @test40(i32 %a, i32 %b) nounwind {
%shl1 = shl i32 1, %b
%shl2 = shl i32 %shl1, 2
%div = udiv i32 %a, %shl2
ret i32 %div
; CHECK: @test40
; CHECK-NEXT: add i32 %b, 2
; CHECK-NEXT: lshr i32 %a
; CHECK-NEXT: ret i32
}
define i32 @test41(i32 %a, i32 %b) nounwind {
%1 = shl i32 1, %b
%2 = shl i32 %1, 3
ret i32 %2
; CHECK: @test41
; CHECK-NEXT: shl i32 8, %b
; CHECK-NEXT: ret i32
}