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[LoopIdiom] 'left-shift until bittest': don't forget to check that PHI node is in loop header 

Fixes an issue reported by Peter Collingbourne in
https://reviews.llvm.org/D91726#2475301
This commit is contained in:
Roman Lebedev 2020-12-30 23:53:23 +03:00
parent 7f221c9196
commit 51879a5256
No known key found for this signature in database
GPG Key ID: 083C3EBB4A1689E0
2 changed files with 83 additions and 2 deletions
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4
llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp
View File

@ -2024,8 +2024,8 @@ static bool detectShiftUntilBitTestIdiom(Loop *CurLoop, Value *&BaseX,
// Step 3: Check if the recurrence is in desirable form.
auto *CurrXPN = dyn_cast<PHINode>(CurrX);
if (!CurrXPN) {
LLVM_DEBUG(dbgs() << DEBUG_TYPE " Not a PHI node.\n");
if (!CurrXPN || CurrXPN->getParent() != LoopHeaderBB) {
LLVM_DEBUG(dbgs() << DEBUG_TYPE " Not an expected PHI node.\n");
return false;
}

81
llvm/test/Transforms/LoopIdiom/X86/left-shift-until-bittest.ll
View File

@ -1812,3 +1812,84 @@ end:
call void @use1(i1 %x.curr.isbitunset)
ret i32 %x.curr
}
; %x.curr is not a PHI node
define i32 @n33(i32 %x, i32 %bit, i32 %x.curr) {
; ALL-LABEL: @n33(
; ALL-NEXT: entry:
; ALL-NEXT: [[BITMASK:%.*]] = shl i32 1, [[BIT:%.*]], [[DBG507:!dbg !.*]]
; ALL-NEXT: call void @llvm.dbg.value(metadata i32 [[BITMASK]], [[META503:metadata !.*]], metadata !DIExpression()), [[DBG507]]
; ALL-NEXT: br label [[LOOP:%.*]], [[DBG508:!dbg !.*]]
; ALL: loop:
; ALL-NEXT: [[X_CURR_BITMASKED:%.*]] = and i32 [[X_CURR:%.*]], [[BITMASK]], [[DBG509:!dbg !.*]]
; ALL-NEXT: call void @llvm.dbg.value(metadata i32 [[X_CURR_BITMASKED]], [[META504:metadata !.*]], metadata !DIExpression()), [[DBG509]]
; ALL-NEXT: [[X_CURR_ISBITUNSET:%.*]] = icmp eq i32 [[X_CURR_BITMASKED]], 0, [[DBG510:!dbg !.*]]
; ALL-NEXT: call void @llvm.dbg.value(metadata i1 [[X_CURR_ISBITUNSET]], [[META505:metadata !.*]], metadata !DIExpression()), [[DBG510]]
; ALL-NEXT: [[X_NEXT:%.*]] = shl i32 [[X_CURR]], 1, [[DBG511:!dbg !.*]]
; ALL-NEXT: call void @llvm.dbg.value(metadata i32 [[X_NEXT]], [[META506:metadata !.*]], metadata !DIExpression()), [[DBG511]]
; ALL-NEXT: br i1 [[X_CURR_ISBITUNSET]], label [[LOOP]], label [[END:%.*]], [[DBG512:!dbg !.*]]
; ALL: end:
; ALL-NEXT: ret i32 [[X_CURR]], [[DBG513:!dbg !.*]]
;
entry:
%bitmask = shl i32 1, %bit
br label %loop
loop:
%x.curr.bitmasked = and i32 %x.curr, %bitmask
%x.curr.isbitunset = icmp eq i32 %x.curr.bitmasked, 0
%x.next = shl i32 %x.curr, 1
br i1 %x.curr.isbitunset, label %loop, label %end
end:
ret i32 %x.curr
}
; %x.curr is a PHI node in a wrong block
define i32 @n34(i32 %bit, i1 %c, i32 %x0, i32 %x1) {
; ALL-LABEL: @n34(
; ALL-NEXT: entry:
; ALL-NEXT: [[BITMASK:%.*]] = shl i32 1, [[BIT:%.*]], [[DBG521:!dbg !.*]]
; ALL-NEXT: call void @llvm.dbg.value(metadata i32 [[BITMASK]], [[META516:metadata !.*]], metadata !DIExpression()), [[DBG521]]
; ALL-NEXT: br i1 [[C:%.*]], label [[BB0:%.*]], label [[BB1:%.*]], [[DBG522:!dbg !.*]]
; ALL: bb0:
; ALL-NEXT: br label [[MERGE:%.*]], [[DBG523:!dbg !.*]]
; ALL: bb1:
; ALL-NEXT: br label [[MERGE]], [[DBG524:!dbg !.*]]
; ALL: merge:
; ALL-NEXT: [[X_CURR:%.*]] = phi i32 [ [[X0:%.*]], [[BB0]] ], [ [[X1:%.*]], [[BB1]] ], [[DBG525:!dbg !.*]]
; ALL-NEXT: call void @llvm.dbg.value(metadata i32 [[X_CURR]], [[META517:metadata !.*]], metadata !DIExpression()), [[DBG525]]
; ALL-NEXT: br label [[LOOP:%.*]], [[DBG526:!dbg !.*]]
; ALL: loop:
; ALL-NEXT: [[X_CURR_BITMASKED:%.*]] = and i32 [[X_CURR]], [[BITMASK]], [[DBG527:!dbg !.*]]
; ALL-NEXT: call void @llvm.dbg.value(metadata i32 [[X_CURR_BITMASKED]], [[META518:metadata !.*]], metadata !DIExpression()), [[DBG527]]
; ALL-NEXT: [[X_CURR_ISBITUNSET:%.*]] = icmp eq i32 [[X_CURR_BITMASKED]], 0, [[DBG528:!dbg !.*]]
; ALL-NEXT: call void @llvm.dbg.value(metadata i1 [[X_CURR_ISBITUNSET]], [[META519:metadata !.*]], metadata !DIExpression()), [[DBG528]]
; ALL-NEXT: [[X_NEXT:%.*]] = shl i32 [[X_CURR]], 1, [[DBG529:!dbg !.*]]
; ALL-NEXT: call void @llvm.dbg.value(metadata i32 [[X_NEXT]], [[META520:metadata !.*]], metadata !DIExpression()), [[DBG529]]
; ALL-NEXT: br i1 [[X_CURR_ISBITUNSET]], label [[LOOP]], label [[END:%.*]], [[DBG530:!dbg !.*]]
; ALL: end:
; ALL-NEXT: ret i32 [[X_CURR]], [[DBG531:!dbg !.*]]
;
entry:
%bitmask = shl i32 1, %bit
br i1 %c, label %bb0, label %bb1
bb0:
br label %merge
bb1:
br label %merge
merge:
%x.curr = phi i32 [ %x0, %bb0 ], [ %x1, %bb1 ]
br label %loop
loop:
%x.curr.bitmasked = and i32 %x.curr, %bitmask
%x.curr.isbitunset = icmp eq i32 %x.curr.bitmasked, 0
%x.next = shl i32 %x.curr, 1
br i1 %x.curr.isbitunset, label %loop, label %end
end:
ret i32 %x.curr
}