Skip to content

[InstCombine] Handle a bitreverse idiom which ends with a bswap #77677

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 2 commits into from
Jan 11, 2024
Merged

[InstCombine] Handle a bitreverse idiom which ends with a bswap #77677

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
fb91a75
[InstCombine] Add pre-commit tests. NFC.
dtcxzyw Jan 10, 2024
0b4083d
[InstCombine] Handle a bitreverse idiom which ends with a bswap
dtcxzyw Jan 10, 2024
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
4 changes: 4 additions & 0 deletions llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -1884,6 +1884,10 @@ Instruction *InstCombinerImpl::visitCallInst(CallInst &CI) {
return crossLogicOpFold;
}

// Try to fold into bitreverse if bswap is the root of the expression tree.
if (Instruction *BitOp = matchBSwapOrBitReverse(*II, /*MatchBSwaps*/ false,
/*MatchBitReversals*/ true))
return BitOp;
break;
}
case Intrinsic::masked_load:
Expand Down
3 changes: 2 additions & 1 deletion llvm/lib/Transforms/Utils/Local.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -3905,7 +3905,8 @@ bool llvm::recognizeBSwapOrBitReverseIdiom(
SmallVectorImpl<Instruction *> &InsertedInsts) {
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())))
!match(I, m_FShr(m_Value(), m_Value(), m_Value())) &&
!match(I, m_BSwap(m_Value())))
return false;
if (!MatchBSwaps && !MatchBitReversals)
return false;
Expand Down
26 changes: 26 additions & 0 deletions llvm/test/Transforms/InstCombine/bitreverse.ll
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -106,6 +106,30 @@ entry:
ret i32 %or.4
}

define i32 @rev32_bswap(i32 %v) {
; CHECK-LABEL: @rev32_bswap(
; CHECK-NEXT: [[RET:%.*]] = call i32 @llvm.bitreverse.i32(i32 [[V:%.*]])
; CHECK-NEXT: ret i32 [[RET]]
;
%and.i = lshr i32 %v, 1
%shr.i = and i32 %and.i, 1431655765
%and1.i = shl i32 %v, 1
%shl.i = and i32 %and1.i, -1431655766
%or.i = or disjoint i32 %shr.i, %shl.i
%and2.i = lshr i32 %or.i, 2
%shr3.i = and i32 %and2.i, 858993459
%and4.i = shl i32 %or.i, 2
%shl5.i = and i32 %and4.i, -858993460
%or6.i = or disjoint i32 %shr3.i, %shl5.i
%and7.i = lshr i32 %or6.i, 4
%shr8.i = and i32 %and7.i, 252645135
%and9.i = shl i32 %or6.i, 4
%shl10.i = and i32 %and9.i, -252645136
%or11.i = or disjoint i32 %shr8.i, %shl10.i
%ret = call i32 @llvm.bswap.i32(i32 %or11.i)
ret i32 %ret
}

define i64 @rev64(i64 %v) {
; CHECK-LABEL: @rev64(
; CHECK-NEXT: entry:
Expand Down Expand Up @@ -508,3 +532,5 @@ define i64 @rev_all_operand64_multiuse_both(i64 %a, i64 %b) #0 {
call void @use_i64(i64 %2)
ret i64 %4
}

declare i32 @llvm.bswap.i32(i32 %or11.i)