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[InstCombine] Adjusting bswap pattern matching to hold for And/Shift mixed case 

Differential Revision: https://reviews.llvm.org/D45731

Change-Id: I85d4226504e954933c41598327c91b2d08192a9d
llvm-svn: 331257
This commit is contained in:
Omer Paparo Bivas 2018-05-01 12:25:46 +00:00
parent 6f710a6440
commit 82ef8e19ef
2 changed files with 14 additions and 6 deletions
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13
llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
View File

@ -1675,7 +1675,18 @@ Instruction *InstCombiner::MatchBSwap(BinaryOperator &I) {
bool OrOfAnds = match(Op0, m_And(m_Value(), m_Value())) &&
match(Op1, m_And(m_Value(), m_Value()));
if (!OrOfOrs && !OrOfShifts && !OrOfAnds)
// (A << B) | (C & D) -> bswap if possible.
// The bigger pattern here is ((A & C1) << C2) | ((B >> C2) & C1), which is a
// part of the bswap idiom for specific values of C1, C2 (e.g. C1 = 16711935,
// C2 = 8 for i32).
// This pattern can occur when the operands of the 'or' are not canonicalized
// for some reason (not having only one use, for example).
bool OrOfAndAndSh = (match(Op0, m_LogicalShift(m_Value(), m_Value())) &&
match(Op1, m_And(m_Value(), m_Value()))) ||
(match(Op0, m_And(m_Value(), m_Value())) &&
match(Op1, m_LogicalShift(m_Value(), m_Value())));
if (!OrOfOrs && !OrOfShifts && !OrOfAnds && !OrOfAndAndSh)
return nullptr;
SmallVector<Instruction*, 4> Insts;

7
llvm/test/Transforms/InstCombine/bswap.ll
View File

@ -116,7 +116,7 @@ define i32 @bswap32_and_first(i32 %x) {
ret i32 %bswap
}
; FIXME: Extra use should not prevent matching to bswap.
; Extra use should not prevent matching to bswap.
; swaphalf = (x << 16 | x >> 16)
; ((swaphalf & 0x00ff00ff) << 8) | ((swaphalf >> 8) & 0x00ff00ff)
@ -126,10 +126,7 @@ define i32 @bswap32_and_first_extra_use(i32 %x) {
; CHECK-NEXT: [[SHR:%.*]] = lshr i32 %x, 16
; CHECK-NEXT: [[SWAPHALF:%.*]] = or i32 [[SHL]], [[SHR]]
; CHECK-NEXT: [[T:%.*]] = and i32 [[SWAPHALF]], 16711935
; CHECK-NEXT: [[TSHL:%.*]] = shl nuw i32 [[T]], 8
; CHECK-NEXT: [[B:%.*]] = lshr i32 [[SWAPHALF]], 8
; CHECK-NEXT: [[BAND:%.*]] = and i32 [[B]], 16711935
; CHECK-NEXT: [[BSWAP:%.*]] = or i32 [[TSHL]], [[BAND]]
; CHECK-NEXT: [[BSWAP:%.*]] = call i32 @llvm.bswap.i32(i32 %x)
; CHECK-NEXT: call void @extra_use(i32 [[T]])
; CHECK-NEXT: ret i32 [[BSWAP]]
;