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[SCEV] Look through single value PHIs.

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Now that SCEVExpander can preserve LCSSA form,
we do not have to worry about LCSSA form when
trying to look through PHIs. SCEVExpander will take
care of inserting LCSSA PHI nodes as required.

This increases precision of the analysis in some cases.

Reviewed By: mkazantsev, bmahjour

Differential Revision: https://reviews.llvm.org/D71539
This commit is contained in:
Florian Hahn 2020-08-12 08:46:07 +01:00
parent cde37ff605
commit 371c1e57df
4 changed files with 22 additions and 43 deletions
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7
lib/Analysis/ScalarEvolution.cpp
View File

@ -5112,13 +5112,8 @@ const SCEV *ScalarEvolution::createNodeForPHI(PHINode *PN) {
if (const SCEV *S = createNodeFromSelectLikePHI(PN))
return S;
// If the PHI has a single incoming value, follow that value, unless the
// PHI's incoming blocks are in a different loop, in which case doing so
// risks breaking LCSSA form. Instcombine would normally zap these, but
// it doesn't have DominatorTree information, so it may miss cases.
if (Value *V = SimplifyInstruction(PN, {getDataLayout(), &TLI, &DT, &AC}))
if (LI.replacementPreservesLCSSAForm(PN, V))
return getSCEV(V);
return getSCEV(V);
// If it's not a loop phi, we can't handle it yet.
return getUnknown(PN);

4
test/Analysis/ScalarEvolution/solve-quadratic-i1.ll
View File

@ -58,9 +58,9 @@ b2: ; preds = %b1
; CHECK-NEXT: %v6 = add nuw nsw i32 %v1, 1
; CHECK-NEXT: --> {4,+,1}<nuw><nsw><%b1> U: [4,7) S: [4,7) Exits: 6 LoopDispositions: { %b1: Computable }
; CHECK-NEXT: %v7 = phi i32 [ %v1, %b1 ]
; CHECK-NEXT: --> %v7 U: [3,6) S: [3,6)
; CHECK-NEXT: --> {3,+,1}<nuw><nsw><%b1> U: [3,6) S: [3,6) --> 5 U: [5,6) S: [5,6)
; CHECK-NEXT: %v8 = phi i16 [ %v3, %b1 ]
; CHECK-NEXT: --> %v8 U: full-set S: full-set
; CHECK-NEXT: --> {3,+,4,+,1}<%b1> U: full-set S: full-set --> 12 U: [12,13) S: [12,13)
; CHECK-NEXT: Determining loop execution counts for: @f1
; CHECK-NEXT: Loop %b3: <multiple exits> Unpredictable backedge-taken count.
; CHECK-NEXT: Loop %b3: Unpredictable max backedge-taken count.

6
test/Analysis/ScalarEvolution/solve-quadratic-overflow.ll
View File

@ -13,11 +13,11 @@
; CHECK-NEXT: %v3 = mul i16 %v2, %v2
; CHECK-NEXT: --> {1,+,3,+,2}<%b1> U: full-set S: full-set Exits: 0 LoopDispositions: { %b1: Computable }
; CHECK-NEXT: %v5 = phi i16 [ %v2, %b1 ]
; CHECK-NEXT: --> %v5 U: [-256,0) S: [-256,0)
; CHECK-NEXT: --> {-1,+,-1}<%b1> U: [-256,0) S: [-256,0) --> -256 U: [-256,-255) S: [-256,-255)
; CHECK-NEXT: %v6 = phi i16 [ %v3, %b1 ]
; CHECK-NEXT: --> %v6 U: full-set S: full-set
; CHECK-NEXT: --> {1,+,3,+,2}<%b1> U: full-set S: full-set --> 0 U: [0,1) S: [0,1)
; CHECK-NEXT: %v7 = sext i16 %v5 to i32
; CHECK-NEXT: --> (sext i16 %v5 to i32) U: [-256,0) S: [-256,0)
; CHECK-NEXT: --> {-1,+,-1}<nsw><%b1> U: [-256,0) S: [-256,0) --> -256 U: [-256,-255) S: [-256,-255)
; CHECK-NEXT: Determining loop execution counts for: @f0
; CHECK-NEXT: Loop %b1: backedge-taken count is 255
; CHECK-NEXT: Loop %b1: max backedge-taken count is 255

48
test/Transforms/LoopStrengthReduce/funclet.ll
View File

@ -15,25 +15,21 @@ define void @f() personality i32 (...)* @_except_handler3 {
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[THROW:%.*]]
; CHECK: throw:
; CHECK-NEXT: [[TMP96:%.*]] = getelementptr inbounds i8, i8* undef, i32 1
; CHECK-NEXT: invoke void @reserve()
; CHECK-NEXT: to label [[THROW]] unwind label [[PAD:%.*]]
; CHECK: pad:
; CHECK-NEXT: [[PHI2:%.*]] = phi i8* [ [[TMP96]], [[THROW]] ]
; CHECK-NEXT: [[CS:%.*]] = catchswitch within none [label %unreachable] unwind label [[BLAH2:%.*]]
; CHECK: unreachable:
; CHECK-NEXT: [[TMP0:%.*]] = catchpad within [[CS]] []
; CHECK-NEXT: unreachable
; CHECK: blah2:
; CHECK-NEXT: [[CLEANUPPADI4_I_I_I:%.*]] = cleanuppad within none []
; CHECK-NEXT: [[PHI21:%.*]] = ptrtoint i8* [[PHI2]] to i32
; CHECK-NEXT: [[TMP1:%.*]] = sub i32 1, [[PHI21]]
; CHECK-NEXT: [[SCEVGEP:%.*]] = getelementptr i8, i8* undef, i32 [[TMP1]]
; CHECK-NEXT: br label [[LOOP_BODY:%.*]]
; CHECK: loop_body:
; CHECK-NEXT: [[LSR_IV:%.*]] = phi i8* [ [[SCEVGEP2:%.*]], [[ITER:%.*]] ], [ [[SCEVGEP]], [[BLAH2]] ]
; CHECK-NEXT: [[SCEVGEP2]] = getelementptr i8, i8* [[LSR_IV]], i32 -1
; CHECK-NEXT: [[TMP100:%.*]] = icmp eq i8* [[SCEVGEP2]], null
; CHECK-NEXT: [[LSR_IV:%.*]] = phi i32 [ [[LSR_IV_NEXT:%.*]], [[ITER:%.*]] ], [ 0, [[BLAH2]] ]
; CHECK-NEXT: [[LSR_IV_NEXT]] = add nuw nsw i32 [[LSR_IV]], -1
; CHECK-NEXT: [[LSR_IV_NEXT1:%.*]] = inttoptr i32 [[LSR_IV_NEXT]] to i8*
; CHECK-NEXT: [[TMP100:%.*]] = icmp eq i8* [[LSR_IV_NEXT1]], null
; CHECK-NEXT: br i1 [[TMP100]], label [[UNWIND_OUT:%.*]], label [[ITER]]
; CHECK: iter:
; CHECK-NEXT: br i1 true, label [[UNWIND_OUT]], label [[LOOP_BODY]]
@ -78,29 +74,25 @@ define void @g() personality i32 (...)* @_except_handler3 {
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[THROW:%.*]]
; CHECK: throw:
; CHECK-NEXT: [[TMP96:%.*]] = getelementptr inbounds i8, i8* undef, i32 1
; CHECK-NEXT: invoke void @reserve()
; CHECK-NEXT: to label [[THROW]] unwind label [[PAD:%.*]]
; CHECK: pad:
; CHECK-NEXT: [[PHI2:%.*]] = phi i8* [ [[TMP96]], [[THROW]] ]
; CHECK-NEXT: [[CS:%.*]] = catchswitch within none [label [[UNREACHABLE:%.*]], label %blah] unwind to caller
; CHECK: unreachable:
; CHECK-NEXT: [[TMP0:%.*]] = catchpad within [[CS]] []
; CHECK-NEXT: unreachable
; CHECK: blah:
; CHECK-NEXT: [[CATCHPAD:%.*]] = catchpad within [[CS]] []
; CHECK-NEXT: [[PHI21:%.*]] = ptrtoint i8* [[PHI2]] to i32
; CHECK-NEXT: [[TMP1:%.*]] = sub i32 1, [[PHI21]]
; CHECK-NEXT: [[SCEVGEP:%.*]] = getelementptr i8, i8* undef, i32 [[TMP1]]
; CHECK-NEXT: br label [[LOOP_BODY:%.*]]
; CHECK: unwind_out:
; CHECK-NEXT: catchret from [[CATCHPAD]] to label [[LEAVE:%.*]]
; CHECK: leave:
; CHECK-NEXT: ret void
; CHECK: loop_body:
; CHECK-NEXT: [[LSR_IV:%.*]] = phi i8* [ [[SCEVGEP2:%.*]], [[ITER:%.*]] ], [ [[SCEVGEP]], [[BLAH:%.*]] ]
; CHECK-NEXT: [[SCEVGEP2]] = getelementptr i8, i8* [[LSR_IV]], i32 -1
; CHECK-NEXT: [[TMP100:%.*]] = icmp eq i8* [[SCEVGEP2]], null
; CHECK-NEXT: [[LSR_IV:%.*]] = phi i32 [ [[LSR_IV_NEXT:%.*]], [[ITER:%.*]] ], [ 0, [[BLAH:%.*]] ]
; CHECK-NEXT: [[LSR_IV_NEXT]] = add nuw nsw i32 [[LSR_IV]], -1
; CHECK-NEXT: [[LSR_IV_NEXT1:%.*]] = inttoptr i32 [[LSR_IV_NEXT]] to i8*
; CHECK-NEXT: [[TMP100:%.*]] = icmp eq i8* [[LSR_IV_NEXT1]], null
; CHECK-NEXT: br i1 [[TMP100]], label [[UNWIND_OUT:%.*]], label [[ITER]]
; CHECK: iter:
; CHECK-NEXT: br i1 true, label [[UNWIND_OUT]], label [[LOOP_BODY]]
@ -146,7 +138,6 @@ define void @h() personality i32 (...)* @_except_handler3 {
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[THROW:%.*]]
; CHECK: throw:
; CHECK-NEXT: [[TMP96:%.*]] = getelementptr inbounds i8, i8* undef, i32 1
; CHECK-NEXT: invoke void @reserve()
; CHECK-NEXT: to label [[THROW]] unwind label [[PAD:%.*]]
; CHECK: pad:
@ -155,20 +146,17 @@ define void @h() personality i32 (...)* @_except_handler3 {
; CHECK-NEXT: [[TMP0:%.*]] = catchpad within [[CS]] []
; CHECK-NEXT: unreachable
; CHECK: blug:
; CHECK-NEXT: [[PHI2:%.*]] = phi i8* [ [[TMP96]], [[PAD]] ]
; CHECK-NEXT: [[CATCHPAD:%.*]] = catchpad within [[CS]] []
; CHECK-NEXT: [[PHI21:%.*]] = ptrtoint i8* [[PHI2]] to i32
; CHECK-NEXT: [[TMP1:%.*]] = sub i32 1, [[PHI21]]
; CHECK-NEXT: [[SCEVGEP:%.*]] = getelementptr i8, i8* undef, i32 [[TMP1]]
; CHECK-NEXT: br label [[LOOP_BODY:%.*]]
; CHECK: unwind_out:
; CHECK-NEXT: catchret from [[CATCHPAD]] to label [[LEAVE:%.*]]
; CHECK: leave:
; CHECK-NEXT: ret void
; CHECK: loop_body:
; CHECK-NEXT: [[LSR_IV:%.*]] = phi i8* [ [[SCEVGEP2:%.*]], [[ITER:%.*]] ], [ [[SCEVGEP]], [[BLUG:%.*]] ]
; CHECK-NEXT: [[SCEVGEP2]] = getelementptr i8, i8* [[LSR_IV]], i32 -1
; CHECK-NEXT: [[TMP100:%.*]] = icmp eq i8* [[SCEVGEP2]], null
; CHECK-NEXT: [[LSR_IV:%.*]] = phi i32 [ [[LSR_IV_NEXT:%.*]], [[ITER:%.*]] ], [ 0, [[BLUG:%.*]] ]
; CHECK-NEXT: [[LSR_IV_NEXT]] = add nuw nsw i32 [[LSR_IV]], -1
; CHECK-NEXT: [[LSR_IV_NEXT1:%.*]] = inttoptr i32 [[LSR_IV_NEXT]] to i8*
; CHECK-NEXT: [[TMP100:%.*]] = icmp eq i8* [[LSR_IV_NEXT1]], null
; CHECK-NEXT: br i1 [[TMP100]], label [[UNWIND_OUT:%.*]], label [[ITER]]
; CHECK: iter:
; CHECK-NEXT: br i1 true, label [[UNWIND_OUT]], label [[LOOP_BODY]]
@ -214,11 +202,9 @@ define void @i() personality i32 (...)* @_except_handler3 {
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[THROW:%.*]]
; CHECK: throw:
; CHECK-NEXT: [[TMP96:%.*]] = getelementptr inbounds i8, i8* undef, i32 1
; CHECK-NEXT: invoke void @reserve()
; CHECK-NEXT: to label [[THROW]] unwind label [[CATCHPAD:%.*]]
; CHECK: catchpad:
; CHECK-NEXT: [[PHI2:%.*]] = phi i8* [ [[TMP96]], [[THROW]] ]
; CHECK-NEXT: [[CS:%.*]] = catchswitch within none [label %cp_body] unwind label [[CLEANUPPAD:%.*]]
; CHECK: cp_body:
; CHECK-NEXT: [[TMP0:%.*]] = catchpad within [[CS]] []
@ -227,14 +213,12 @@ define void @i() personality i32 (...)* @_except_handler3 {
; CHECK-NEXT: [[TMP1:%.*]] = cleanuppad within none []
; CHECK-NEXT: br label [[LOOP_HEAD]]
; CHECK: loop_head:
; CHECK-NEXT: [[PHI21:%.*]] = ptrtoint i8* [[PHI2]] to i32
; CHECK-NEXT: [[TMP2:%.*]] = sub i32 1, [[PHI21]]
; CHECK-NEXT: [[SCEVGEP:%.*]] = getelementptr i8, i8* undef, i32 [[TMP2]]
; CHECK-NEXT: br label [[LOOP_BODY:%.*]]
; CHECK: loop_body:
; CHECK-NEXT: [[LSR_IV:%.*]] = phi i8* [ [[SCEVGEP2:%.*]], [[ITER:%.*]] ], [ [[SCEVGEP]], [[LOOP_HEAD]] ]
; CHECK-NEXT: [[SCEVGEP2]] = getelementptr i8, i8* [[LSR_IV]], i32 -1
; CHECK-NEXT: [[TMP100:%.*]] = icmp eq i8* [[SCEVGEP2]], null
; CHECK-NEXT: [[LSR_IV:%.*]] = phi i32 [ [[LSR_IV_NEXT:%.*]], [[ITER:%.*]] ], [ 0, [[LOOP_HEAD]] ]
; CHECK-NEXT: [[LSR_IV_NEXT]] = add nuw nsw i32 [[LSR_IV]], -1
; CHECK-NEXT: [[LSR_IV_NEXT1:%.*]] = inttoptr i32 [[LSR_IV_NEXT]] to i8*
; CHECK-NEXT: [[TMP100:%.*]] = icmp eq i8* [[LSR_IV_NEXT1]], null
; CHECK-NEXT: br i1 [[TMP100]], label [[UNWIND_OUT:%.*]], label [[ITER]]
; CHECK: iter:
; CHECK-NEXT: br i1 true, label [[UNWIND_OUT]], label [[LOOP_BODY]]