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[Utils] recognizeBSwapOrBitReverseIdiom - support matching from funnel shift roots (PR40058) 

We were missing bitreverse matches in cases where InstCombine had seen a byte-level rotation at the end of a bitreverse sequence (replacing or() with fshl()), hindering the exhaustive bitreverse matching in CodeGenPrepare later on.
This commit is contained in:
Simon Pilgrim 2021-05-04 13:46:45 +01:00
parent e0dd708f40
commit 2bb41851a1
2 changed files with 5 additions and 28 deletions
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4
llvm/lib/Transforms/Utils/Local.cpp
View File

@ -3101,7 +3101,9 @@ static bool bitTransformIsCorrectForBitReverse(unsigned From, unsigned To,
bool llvm::recognizeBSwapOrBitReverseIdiom(
Instruction *I, bool MatchBSwaps, bool MatchBitReversals,
SmallVectorImpl<Instruction *> &InsertedInsts) {
if (Operator::getOpcode(I) != Instruction::Or)
if (!match(I, m_Or(m_Value(), m_Value())) &&
!match(I, m_FShl(m_Value(), m_Value(), m_Value())) &&
!match(I, m_FShr(m_Value(), m_Value(), m_Value())))
return false;
if (!MatchBSwaps && !MatchBitReversals)
return false;

29
llvm/test/Transforms/CodeGenPrepare/X86/bitreverse-recognize.ll
View File

@ -29,33 +29,8 @@ for.body: ; preds = %for.body, %entry
; PR40058
define i64 @bitreverse_i64(i64 %0) {
; CHECK-LABEL: @bitreverse_i64(
; CHECK-NEXT: [[TMP2:%.*]] = lshr i64 [[TMP0:%.*]], 1
; CHECK-NEXT: [[TMP3:%.*]] = and i64 [[TMP2]], 6148914691236517205
; CHECK-NEXT: [[TMP4:%.*]] = shl i64 [[TMP0]], 1
; CHECK-NEXT: [[TMP5:%.*]] = and i64 [[TMP4]], -6148914691236517206
; CHECK-NEXT: [[TMP6:%.*]] = or i64 [[TMP3]], [[TMP5]]
; CHECK-NEXT: [[TMP7:%.*]] = lshr i64 [[TMP6]], 2
; CHECK-NEXT: [[TMP8:%.*]] = and i64 [[TMP7]], 3689348814741910323
; CHECK-NEXT: [[TMP9:%.*]] = shl i64 [[TMP6]], 2
; CHECK-NEXT: [[TMP10:%.*]] = and i64 [[TMP9]], -3689348814741910324
; CHECK-NEXT: [[TMP11:%.*]] = or i64 [[TMP8]], [[TMP10]]
; CHECK-NEXT: [[TMP12:%.*]] = lshr i64 [[TMP11]], 4
; CHECK-NEXT: [[TMP13:%.*]] = and i64 [[TMP12]], 1085102592571150095
; CHECK-NEXT: [[TMP14:%.*]] = shl i64 [[TMP11]], 4
; CHECK-NEXT: [[TMP15:%.*]] = and i64 [[TMP14]], -1085102592571150096
; CHECK-NEXT: [[TMP16:%.*]] = or i64 [[TMP13]], [[TMP15]]
; CHECK-NEXT: [[TMP17:%.*]] = lshr i64 [[TMP16]], 8
; CHECK-NEXT: [[TMP18:%.*]] = and i64 [[TMP17]], 71777214294589695
; CHECK-NEXT: [[TMP19:%.*]] = shl i64 [[TMP16]], 8
; CHECK-NEXT: [[TMP20:%.*]] = and i64 [[TMP19]], -71777214294589696
; CHECK-NEXT: [[TMP21:%.*]] = or i64 [[TMP18]], [[TMP20]]
; CHECK-NEXT: [[TMP22:%.*]] = lshr i64 [[TMP21]], 16
; CHECK-NEXT: [[TMP23:%.*]] = and i64 [[TMP22]], 281470681808895
; CHECK-NEXT: [[TMP24:%.*]] = shl i64 [[TMP21]], 16
; CHECK-NEXT: [[TMP25:%.*]] = and i64 [[TMP24]], -281470681808896
; CHECK-NEXT: [[TMP26:%.*]] = or i64 [[TMP23]], [[TMP25]]
; CHECK-NEXT: [[TMP27:%.*]] = tail call i64 @llvm.fshl.i64(i64 [[TMP26]], i64 [[TMP26]], i64 32)
; CHECK-NEXT: ret i64 [[TMP27]]
; CHECK-NEXT: [[REV:%.*]] = call i64 @llvm.bitreverse.i64(i64 [[TMP0:%.*]])
; CHECK-NEXT: ret i64 [[REV]]
;
%2 = lshr i64 %0, 1
%3 = and i64 %2, 6148914691236517205