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[SCEV] Look through single value PHIs.
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
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4 files changed

+22
-43
lines changed

4 files changed

+22
-43
lines changed

‎llvm/lib/Analysis/ScalarEvolution.cpp

Lines changed: 1 addition & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -5112,13 +5112,8 @@ const SCEV *ScalarEvolution::createNodeForPHI(PHINode *PN) {
51125112
if (const SCEV *S = createNodeFromSelectLikePHI(PN))
51135113
return S;
51145114

5115-
// If the PHI has a single incoming value, follow that value, unless the
5116-
// PHI's incoming blocks are in a different loop, in which case doing so
5117-
// risks breaking LCSSA form. Instcombine would normally zap these, but
5118-
// it doesn't have DominatorTree information, so it may miss cases.
51195115
if (Value *V = SimplifyInstruction(PN, {getDataLayout(), &TLI, &DT, &AC}))
5120-
if (LI.replacementPreservesLCSSAForm(PN, V))
5121-
return getSCEV(V);
5116+
return getSCEV(V);
51225117

51235118
// If it's not a loop phi, we can't handle it yet.
51245119
return getUnknown(PN);

‎llvm/test/Analysis/ScalarEvolution/solve-quadratic-i1.ll

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -58,9 +58,9 @@ b2: ; preds = %b1
5858
; CHECK-NEXT: %v6 = add nuw nsw i32 %v1, 1
5959
; CHECK-NEXT: --> {4,+,1}<nuw><nsw><%b1> U: [4,7) S: [4,7) Exits: 6 LoopDispositions: { %b1: Computable }
6060
; CHECK-NEXT: %v7 = phi i32 [ %v1, %b1 ]
61-
; CHECK-NEXT: --> %v7 U: [3,6) S: [3,6)
61+
; CHECK-NEXT: --> {3,+,1}<nuw><nsw><%b1> U: [3,6) S: [3,6) --> 5 U: [5,6) S: [5,6)
6262
; CHECK-NEXT: %v8 = phi i16 [ %v3, %b1 ]
63-
; CHECK-NEXT: --> %v8 U: full-set S: full-set
63+
; CHECK-NEXT: --> {3,+,4,+,1}<%b1> U: full-set S: full-set --> 12 U: [12,13) S: [12,13)
6464
; CHECK-NEXT: Determining loop execution counts for: @f1
6565
; CHECK-NEXT: Loop %b3: <multiple exits> Unpredictable backedge-taken count.
6666
; CHECK-NEXT: Loop %b3: Unpredictable max backedge-taken count.

‎llvm/test/Analysis/ScalarEvolution/solve-quadratic-overflow.ll

Lines changed: 3 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -13,11 +13,11 @@
1313
; CHECK-NEXT: %v3 = mul i16 %v2, %v2
1414
; CHECK-NEXT: --> {1,+,3,+,2}<%b1> U: full-set S: full-set Exits: 0 LoopDispositions: { %b1: Computable }
1515
; CHECK-NEXT: %v5 = phi i16 [ %v2, %b1 ]
16-
; CHECK-NEXT: --> %v5 U: [-256,0) S: [-256,0)
16+
; CHECK-NEXT: --> {-1,+,-1}<%b1> U: [-256,0) S: [-256,0) --> -256 U: [-256,-255) S: [-256,-255)
1717
; CHECK-NEXT: %v6 = phi i16 [ %v3, %b1 ]
18-
; CHECK-NEXT: --> %v6 U: full-set S: full-set
18+
; CHECK-NEXT: --> {1,+,3,+,2}<%b1> U: full-set S: full-set --> 0 U: [0,1) S: [0,1)
1919
; CHECK-NEXT: %v7 = sext i16 %v5 to i32
20-
; CHECK-NEXT: --> (sext i16 %v5 to i32) U: [-256,0) S: [-256,0)
20+
; CHECK-NEXT: --> {-1,+,-1}<nsw><%b1> U: [-256,0) S: [-256,0) --> -256 U: [-256,-255) S: [-256,-255)
2121
; CHECK-NEXT: Determining loop execution counts for: @f0
2222
; CHECK-NEXT: Loop %b1: backedge-taken count is 255
2323
; CHECK-NEXT: Loop %b1: max backedge-taken count is 255

‎llvm/test/Transforms/LoopStrengthReduce/funclet.ll

Lines changed: 16 additions & 32 deletions
Original file line numberDiff line numberDiff line change
@@ -15,25 +15,21 @@ define void @f() personality i32 (...)* @_except_handler3 {
1515
; CHECK-NEXT: entry:
1616
; CHECK-NEXT: br label [[THROW:%.*]]
1717
; CHECK: throw:
18-
; CHECK-NEXT: [[TMP96:%.*]] = getelementptr inbounds i8, i8* undef, i32 1
1918
; CHECK-NEXT: invoke void @reserve()
2019
; CHECK-NEXT: to label [[THROW]] unwind label [[PAD:%.*]]
2120
; CHECK: pad:
22-
; CHECK-NEXT: [[PHI2:%.*]] = phi i8* [ [[TMP96]], [[THROW]] ]
2321
; CHECK-NEXT: [[CS:%.*]] = catchswitch within none [label %unreachable] unwind label [[BLAH2:%.*]]
2422
; CHECK: unreachable:
2523
; CHECK-NEXT: [[TMP0:%.*]] = catchpad within [[CS]] []
2624
; CHECK-NEXT: unreachable
2725
; CHECK: blah2:
2826
; CHECK-NEXT: [[CLEANUPPADI4_I_I_I:%.*]] = cleanuppad within none []
29-
; CHECK-NEXT: [[PHI21:%.*]] = ptrtoint i8* [[PHI2]] to i32
30-
; CHECK-NEXT: [[TMP1:%.*]] = sub i32 1, [[PHI21]]
31-
; CHECK-NEXT: [[SCEVGEP:%.*]] = getelementptr i8, i8* undef, i32 [[TMP1]]
3227
; CHECK-NEXT: br label [[LOOP_BODY:%.*]]
3328
; CHECK: loop_body:
34-
; CHECK-NEXT: [[LSR_IV:%.*]] = phi i8* [ [[SCEVGEP2:%.*]], [[ITER:%.*]] ], [ [[SCEVGEP]], [[BLAH2]] ]
35-
; CHECK-NEXT: [[SCEVGEP2]] = getelementptr i8, i8* [[LSR_IV]], i32 -1
36-
; CHECK-NEXT: [[TMP100:%.*]] = icmp eq i8* [[SCEVGEP2]], null
29+
; CHECK-NEXT: [[LSR_IV:%.*]] = phi i32 [ [[LSR_IV_NEXT:%.*]], [[ITER:%.*]] ], [ 0, [[BLAH2]] ]
30+
; CHECK-NEXT: [[LSR_IV_NEXT]] = add nuw nsw i32 [[LSR_IV]], -1
31+
; CHECK-NEXT: [[LSR_IV_NEXT1:%.*]] = inttoptr i32 [[LSR_IV_NEXT]] to i8*
32+
; CHECK-NEXT: [[TMP100:%.*]] = icmp eq i8* [[LSR_IV_NEXT1]], null
3733
; CHECK-NEXT: br i1 [[TMP100]], label [[UNWIND_OUT:%.*]], label [[ITER]]
3834
; CHECK: iter:
3935
; CHECK-NEXT: br i1 true, label [[UNWIND_OUT]], label [[LOOP_BODY]]
@@ -78,29 +74,25 @@ define void @g() personality i32 (...)* @_except_handler3 {
7874
; CHECK-NEXT: entry:
7975
; CHECK-NEXT: br label [[THROW:%.*]]
8076
; CHECK: throw:
81-
; CHECK-NEXT: [[TMP96:%.*]] = getelementptr inbounds i8, i8* undef, i32 1
8277
; CHECK-NEXT: invoke void @reserve()
8378
; CHECK-NEXT: to label [[THROW]] unwind label [[PAD:%.*]]
8479
; CHECK: pad:
85-
; CHECK-NEXT: [[PHI2:%.*]] = phi i8* [ [[TMP96]], [[THROW]] ]
8680
; CHECK-NEXT: [[CS:%.*]] = catchswitch within none [label [[UNREACHABLE:%.*]], label %blah] unwind to caller
8781
; CHECK: unreachable:
8882
; CHECK-NEXT: [[TMP0:%.*]] = catchpad within [[CS]] []
8983
; CHECK-NEXT: unreachable
9084
; CHECK: blah:
9185
; CHECK-NEXT: [[CATCHPAD:%.*]] = catchpad within [[CS]] []
92-
; CHECK-NEXT: [[PHI21:%.*]] = ptrtoint i8* [[PHI2]] to i32
93-
; CHECK-NEXT: [[TMP1:%.*]] = sub i32 1, [[PHI21]]
94-
; CHECK-NEXT: [[SCEVGEP:%.*]] = getelementptr i8, i8* undef, i32 [[TMP1]]
9586
; CHECK-NEXT: br label [[LOOP_BODY:%.*]]
9687
; CHECK: unwind_out:
9788
; CHECK-NEXT: catchret from [[CATCHPAD]] to label [[LEAVE:%.*]]
9889
; CHECK: leave:
9990
; CHECK-NEXT: ret void
10091
; CHECK: loop_body:
101-
; CHECK-NEXT: [[LSR_IV:%.*]] = phi i8* [ [[SCEVGEP2:%.*]], [[ITER:%.*]] ], [ [[SCEVGEP]], [[BLAH:%.*]] ]
102-
; CHECK-NEXT: [[SCEVGEP2]] = getelementptr i8, i8* [[LSR_IV]], i32 -1
103-
; CHECK-NEXT: [[TMP100:%.*]] = icmp eq i8* [[SCEVGEP2]], null
92+
; CHECK-NEXT: [[LSR_IV:%.*]] = phi i32 [ [[LSR_IV_NEXT:%.*]], [[ITER:%.*]] ], [ 0, [[BLAH:%.*]] ]
93+
; CHECK-NEXT: [[LSR_IV_NEXT]] = add nuw nsw i32 [[LSR_IV]], -1
94+
; CHECK-NEXT: [[LSR_IV_NEXT1:%.*]] = inttoptr i32 [[LSR_IV_NEXT]] to i8*
95+
; CHECK-NEXT: [[TMP100:%.*]] = icmp eq i8* [[LSR_IV_NEXT1]], null
10496
; CHECK-NEXT: br i1 [[TMP100]], label [[UNWIND_OUT:%.*]], label [[ITER]]
10597
; CHECK: iter:
10698
; CHECK-NEXT: br i1 true, label [[UNWIND_OUT]], label [[LOOP_BODY]]
@@ -146,7 +138,6 @@ define void @h() personality i32 (...)* @_except_handler3 {
146138
; CHECK-NEXT: entry:
147139
; CHECK-NEXT: br label [[THROW:%.*]]
148140
; CHECK: throw:
149-
; CHECK-NEXT: [[TMP96:%.*]] = getelementptr inbounds i8, i8* undef, i32 1
150141
; CHECK-NEXT: invoke void @reserve()
151142
; CHECK-NEXT: to label [[THROW]] unwind label [[PAD:%.*]]
152143
; CHECK: pad:
@@ -155,20 +146,17 @@ define void @h() personality i32 (...)* @_except_handler3 {
155146
; CHECK-NEXT: [[TMP0:%.*]] = catchpad within [[CS]] []
156147
; CHECK-NEXT: unreachable
157148
; CHECK: blug:
158-
; CHECK-NEXT: [[PHI2:%.*]] = phi i8* [ [[TMP96]], [[PAD]] ]
159149
; CHECK-NEXT: [[CATCHPAD:%.*]] = catchpad within [[CS]] []
160-
; CHECK-NEXT: [[PHI21:%.*]] = ptrtoint i8* [[PHI2]] to i32
161-
; CHECK-NEXT: [[TMP1:%.*]] = sub i32 1, [[PHI21]]
162-
; CHECK-NEXT: [[SCEVGEP:%.*]] = getelementptr i8, i8* undef, i32 [[TMP1]]
163150
; CHECK-NEXT: br label [[LOOP_BODY:%.*]]
164151
; CHECK: unwind_out:
165152
; CHECK-NEXT: catchret from [[CATCHPAD]] to label [[LEAVE:%.*]]
166153
; CHECK: leave:
167154
; CHECK-NEXT: ret void
168155
; CHECK: loop_body:
169-
; CHECK-NEXT: [[LSR_IV:%.*]] = phi i8* [ [[SCEVGEP2:%.*]], [[ITER:%.*]] ], [ [[SCEVGEP]], [[BLUG:%.*]] ]
170-
; CHECK-NEXT: [[SCEVGEP2]] = getelementptr i8, i8* [[LSR_IV]], i32 -1
171-
; CHECK-NEXT: [[TMP100:%.*]] = icmp eq i8* [[SCEVGEP2]], null
156+
; CHECK-NEXT: [[LSR_IV:%.*]] = phi i32 [ [[LSR_IV_NEXT:%.*]], [[ITER:%.*]] ], [ 0, [[BLUG:%.*]] ]
157+
; CHECK-NEXT: [[LSR_IV_NEXT]] = add nuw nsw i32 [[LSR_IV]], -1
158+
; CHECK-NEXT: [[LSR_IV_NEXT1:%.*]] = inttoptr i32 [[LSR_IV_NEXT]] to i8*
159+
; CHECK-NEXT: [[TMP100:%.*]] = icmp eq i8* [[LSR_IV_NEXT1]], null
172160
; CHECK-NEXT: br i1 [[TMP100]], label [[UNWIND_OUT:%.*]], label [[ITER]]
173161
; CHECK: iter:
174162
; CHECK-NEXT: br i1 true, label [[UNWIND_OUT]], label [[LOOP_BODY]]
@@ -214,11 +202,9 @@ define void @i() personality i32 (...)* @_except_handler3 {
214202
; CHECK-NEXT: entry:
215203
; CHECK-NEXT: br label [[THROW:%.*]]
216204
; CHECK: throw:
217-
; CHECK-NEXT: [[TMP96:%.*]] = getelementptr inbounds i8, i8* undef, i32 1
218205
; CHECK-NEXT: invoke void @reserve()
219206
; CHECK-NEXT: to label [[THROW]] unwind label [[CATCHPAD:%.*]]
220207
; CHECK: catchpad:
221-
; CHECK-NEXT: [[PHI2:%.*]] = phi i8* [ [[TMP96]], [[THROW]] ]
222208
; CHECK-NEXT: [[CS:%.*]] = catchswitch within none [label %cp_body] unwind label [[CLEANUPPAD:%.*]]
223209
; CHECK: cp_body:
224210
; CHECK-NEXT: [[TMP0:%.*]] = catchpad within [[CS]] []
@@ -227,14 +213,12 @@ define void @i() personality i32 (...)* @_except_handler3 {
227213
; CHECK-NEXT: [[TMP1:%.*]] = cleanuppad within none []
228214
; CHECK-NEXT: br label [[LOOP_HEAD]]
229215
; CHECK: loop_head:
230-
; CHECK-NEXT: [[PHI21:%.*]] = ptrtoint i8* [[PHI2]] to i32
231-
; CHECK-NEXT: [[TMP2:%.*]] = sub i32 1, [[PHI21]]
232-
; CHECK-NEXT: [[SCEVGEP:%.*]] = getelementptr i8, i8* undef, i32 [[TMP2]]
233216
; CHECK-NEXT: br label [[LOOP_BODY:%.*]]
234217
; CHECK: loop_body:
235-
; CHECK-NEXT: [[LSR_IV:%.*]] = phi i8* [ [[SCEVGEP2:%.*]], [[ITER:%.*]] ], [ [[SCEVGEP]], [[LOOP_HEAD]] ]
236-
; CHECK-NEXT: [[SCEVGEP2]] = getelementptr i8, i8* [[LSR_IV]], i32 -1
237-
; CHECK-NEXT: [[TMP100:%.*]] = icmp eq i8* [[SCEVGEP2]], null
218+
; CHECK-NEXT: [[LSR_IV:%.*]] = phi i32 [ [[LSR_IV_NEXT:%.*]], [[ITER:%.*]] ], [ 0, [[LOOP_HEAD]] ]
219+
; CHECK-NEXT: [[LSR_IV_NEXT]] = add nuw nsw i32 [[LSR_IV]], -1
220+
; CHECK-NEXT: [[LSR_IV_NEXT1:%.*]] = inttoptr i32 [[LSR_IV_NEXT]] to i8*
221+
; CHECK-NEXT: [[TMP100:%.*]] = icmp eq i8* [[LSR_IV_NEXT1]], null
238222
; CHECK-NEXT: br i1 [[TMP100]], label [[UNWIND_OUT:%.*]], label [[ITER]]
239223
; CHECK: iter:
240224
; CHECK-NEXT: br i1 true, label [[UNWIND_OUT]], label [[LOOP_BODY]]

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