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Revert f0c2a5a "[LV] Generalize conditions for sinking instrs for first order recurrences."
It broke Chromium, causing "Instruction does not dominate all uses!" errors. See https://bugs.chromium.org/p/chromium/issues/detail?id=1022297#c1 for a reproducer. > If the recurrence PHI node has a single user, we can sink any > instruction without side effects, given that all users are dominated by > the instruction computing the incoming value of the next iteration > ('Previous'). We can sink instructions that may cause traps, because > that only causes the trap to occur later, but not on any new paths. > > With the relaxed check, we also have to make sure that we do not have a > direct cycle (meaning PHI user == 'Previous), which indicates a > reduction relation, which potentially gets missed by > ReductionDescriptor. > > As follow-ups, we can also sink stores, iff they do not alias with > other instructions we move them across and we could also support sinking > chains of instructions and multiple users of the PHI. > > Fixes PR43398. > > Reviewers: hsaito, dcaballe, Ayal, rengolin > > Reviewed By: Ayal > > Differential Revision: https://reviews.llvm.org/D69228
This commit is contained in:
Hans Wennborg
parent
0607d36922
commit
173103be2a
@ -699,37 +699,25 @@ bool RecurrenceDescriptor::isFirstOrderRecurrence(
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// Ensure every user of the phi node is dominated by the previous value.
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// The dominance requirement ensures the loop vectorizer will not need to
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// vectorize the initial value prior to the first iteration of the loop.
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// TODO: Consider extending this sinking to handle memory instructions and
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// phis with multiple users.
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// Returns true, if all users of I are dominated by DominatedBy.
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auto allUsesDominatedBy = [DT](Instruction *I, Instruction *DominatedBy) {
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return all_of(I->uses(), [DT, DominatedBy](Use &U) {
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return DT->dominates(DominatedBy, U);
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});
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};
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// TODO: Consider extending this sinking to handle other kinds of instructions
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// and expressions, beyond sinking a single cast past Previous.
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if (Phi->hasOneUse()) {
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Instruction *I = Phi->user_back();
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// If the user of the PHI is also the incoming value, we potentially have a
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// reduction and which cannot be handled by sinking.
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if (Previous == I)
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return false;
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if (DT->dominates(Previous, I)) // We already are good w/o sinking.
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return true;
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// We can sink any instruction without side effects, as long as all users
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// are dominated by the instruction we are sinking after.
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if (I->getParent() == Phi->getParent() && !I->mayHaveSideEffects() &&
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allUsesDominatedBy(I, Previous)) {
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SinkAfter[I] = Previous;
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auto *I = Phi->user_back();
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if (I->isCast() && (I->getParent() == Phi->getParent()) && I->hasOneUse() &&
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DT->dominates(Previous, I->user_back())) {
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if (!DT->dominates(Previous, I)) // Otherwise we're good w/o sinking.
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SinkAfter[I] = Previous;
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return true;
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}
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}
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return allUsesDominatedBy(Phi, Previous);
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for (User *U : Phi->users())
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if (auto *I = dyn_cast<Instruction>(U)) {
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if (!DT->dominates(Previous, I))
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return false;
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}
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return true;
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}
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/// This function returns the identity element (or neutral element) for
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@ -1,245 +0,0 @@
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; RUN: opt -loop-vectorize -force-vector-width=4 -force-vector-interleave=1 -S %s | FileCheck %s
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@p = external local_unnamed_addr global [257 x i32], align 16
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@q = external local_unnamed_addr global [257 x i32], align 16
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; Test case for PR43398.
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define void @can_sink_after_store(i32 %x, i32* %ptr, i64 %tc) local_unnamed_addr #0 {
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; CHECK-LABEL: vector.ph:
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; CHECK: %broadcast.splatinsert1 = insertelement <4 x i32> undef, i32 %x, i32 0
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; CHECK-NEXT: %broadcast.splat2 = shufflevector <4 x i32> %broadcast.splatinsert1, <4 x i32> undef, <4 x i32> zeroinitializer
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; CHECK-NEXT: %vector.recur.init = insertelement <4 x i32> undef, i32 %.pre, i32 3
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; CHECK-NEXT: br label %vector.body
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; CHECK-LABEL: vector.body:
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; CHECK-NEXT: %index = phi i64 [ 0, %vector.ph ], [ %index.next, %vector.body ]
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; CHECK-NEXT: %vector.recur = phi <4 x i32> [ %vector.recur.init, %vector.ph ], [ %wide.load, %vector.body ]
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; CHECK-NEXT: %offset.idx = add i64 1, %index
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; CHECK-NEXT: %broadcast.splatinsert = insertelement <4 x i64> undef, i64 %offset.idx, i32 0
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; CHECK-NEXT: %broadcast.splat = shufflevector <4 x i64> %broadcast.splatinsert, <4 x i64> undef, <4 x i32> zeroinitializer
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; CHECK-NEXT: %induction = add <4 x i64> %broadcast.splat, <i64 0, i64 1, i64 2, i64 3>
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; CHECK-NEXT: %0 = add i64 %offset.idx, 0
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; CHECK-NEXT: %1 = getelementptr inbounds [257 x i32], [257 x i32]* @p, i64 0, i64 %0
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; CHECK-NEXT: %2 = getelementptr inbounds i32, i32* %1, i32 0
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; CHECK-NEXT: %3 = bitcast i32* %2 to <4 x i32>*
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; CHECK-NEXT: %wide.load = load <4 x i32>, <4 x i32>* %3, align 4
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; CHECK-NEXT: %4 = shufflevector <4 x i32> %vector.recur, <4 x i32> %wide.load, <4 x i32> <i32 3, i32 4, i32 5, i32 6>
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; CHECK-NEXT: %5 = add <4 x i32> %4, %broadcast.splat2
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; CHECK-NEXT: %6 = add <4 x i32> %5, %wide.load
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; CHECK-NEXT: %7 = getelementptr inbounds [257 x i32], [257 x i32]* @q, i64 0, i64 %0
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; CHECK-NEXT: %8 = getelementptr inbounds i32, i32* %7, i32 0
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; CHECK-NEXT: %9 = bitcast i32* %8 to <4 x i32>*
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; CHECK-NEXT: store <4 x i32> %6, <4 x i32>* %9, align 4
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; CHECK-NEXT: %index.next = add i64 %index, 4
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; CHECK-NEXT: %10 = icmp eq i64 %index.next, 1996
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; CHECK-NEXT: br i1 %10, label %middle.block, label %vector.body
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;
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entry:
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br label %preheader
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preheader:
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%idx.phi.trans = getelementptr inbounds [257 x i32], [257 x i32]* @p, i64 0, i64 1
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%.pre = load i32, i32* %idx.phi.trans, align 4
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br label %for
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for:
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%pre.phi = phi i32 [ %.pre, %preheader ], [ %pre.next, %for ]
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%iv = phi i64 [ 1, %preheader ], [ %iv.next, %for ]
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%add.1 = add i32 %pre.phi, %x
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%idx.1 = getelementptr inbounds [257 x i32], [257 x i32]* @p, i64 0, i64 %iv
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%pre.next = load i32, i32* %idx.1, align 4
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%add.2 = add i32 %add.1, %pre.next
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%idx.2 = getelementptr inbounds [257 x i32], [257 x i32]* @q, i64 0, i64 %iv
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store i32 %add.2, i32* %idx.2, align 4
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%iv.next = add nuw nsw i64 %iv, 1
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%exitcond = icmp eq i64 %iv.next, 2000
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br i1 %exitcond, label %exit, label %for
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exit:
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ret void
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}
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; We can sink potential trapping instructions, as this will only delay the trap
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; and not introduce traps on additional paths.
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define void @sink_sdiv(i32 %x, i32* %ptr, i64 %tc) local_unnamed_addr #0 {
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; CHECK-LABEL: vector.ph:
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; CHECK: %broadcast.splatinsert1 = insertelement <4 x i32> undef, i32 %x, i32 0
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; CHECK-NEXT: %broadcast.splat2 = shufflevector <4 x i32> %broadcast.splatinsert1, <4 x i32> undef, <4 x i32> zeroinitializer
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; CHECK-NEXT: %vector.recur.init = insertelement <4 x i32> undef, i32 %.pre, i32 3
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; CHECK-NEXT: br label %vector.body
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; CHECK-LABEL: vector.body:
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; CHECK-NEXT: %index = phi i64 [ 0, %vector.ph ], [ %index.next, %vector.body ]
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; CHECK-NEXT: %vector.recur = phi <4 x i32> [ %vector.recur.init, %vector.ph ], [ %wide.load, %vector.body ]
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; CHECK-NEXT: %offset.idx = add i64 1, %index
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; CHECK-NEXT: %broadcast.splatinsert = insertelement <4 x i64> undef, i64 %offset.idx, i32 0
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; CHECK-NEXT: %broadcast.splat = shufflevector <4 x i64> %broadcast.splatinsert, <4 x i64> undef, <4 x i32> zeroinitializer
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; CHECK-NEXT: %induction = add <4 x i64> %broadcast.splat, <i64 0, i64 1, i64 2, i64 3>
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; CHECK-NEXT: %0 = add i64 %offset.idx, 0
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; CHECK-NEXT: %1 = getelementptr inbounds [257 x i32], [257 x i32]* @p, i64 0, i64 %0
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; CHECK-NEXT: %2 = getelementptr inbounds i32, i32* %1, i32 0
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; CHECK-NEXT: %3 = bitcast i32* %2 to <4 x i32>*
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; CHECK-NEXT: %wide.load = load <4 x i32>, <4 x i32>* %3, align 4
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; CHECK-NEXT: %4 = shufflevector <4 x i32> %vector.recur, <4 x i32> %wide.load, <4 x i32> <i32 3, i32 4, i32 5, i32 6>
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; CHECK-NEXT: %5 = sdiv <4 x i32> %4, %broadcast.splat2
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; CHECK-NEXT: %6 = add <4 x i32> %5, %wide.load
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; CHECK-NEXT: %7 = getelementptr inbounds [257 x i32], [257 x i32]* @q, i64 0, i64 %0
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; CHECK-NEXT: %8 = getelementptr inbounds i32, i32* %7, i32 0
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; CHECK-NEXT: %9 = bitcast i32* %8 to <4 x i32>*
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; CHECK-NEXT: store <4 x i32> %6, <4 x i32>* %9, align 4
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; CHECK-NEXT: %index.next = add i64 %index, 4
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; CHECK-NEXT: %10 = icmp eq i64 %index.next, 1996
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; CHECK-NEXT: br i1 %10, label %middle.block, label %vector.body
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;
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entry:
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br label %preheader
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preheader:
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%idx.phi.trans = getelementptr inbounds [257 x i32], [257 x i32]* @p, i64 0, i64 1
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%.pre = load i32, i32* %idx.phi.trans, align 4
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br label %for
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for:
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%pre.phi = phi i32 [ %.pre, %preheader ], [ %pre.next, %for ]
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%iv = phi i64 [ 1, %preheader ], [ %iv.next, %for ]
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%div.1 = sdiv i32 %pre.phi, %x
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%idx.1 = getelementptr inbounds [257 x i32], [257 x i32]* @p, i64 0, i64 %iv
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%pre.next = load i32, i32* %idx.1, align 4
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%add.2 = add i32 %div.1, %pre.next
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%idx.2 = getelementptr inbounds [257 x i32], [257 x i32]* @q, i64 0, i64 %iv
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store i32 %add.2, i32* %idx.2, align 4
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%iv.next = add nuw nsw i64 %iv, 1
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%exitcond = icmp eq i64 %iv.next, 2000
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br i1 %exitcond, label %exit, label %for
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exit:
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ret void
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}
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; FIXME: Currently we can only sink a single instruction. For the example below,
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; we also have to sink users.
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define void @cannot_sink_with_additional_user(i32 %x, i32* %ptr, i64 %tc) {
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; CHECK-LABEL: define void @cannot_sink_with_additional_user(
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; CHECK-NEXT: entry:
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; CHECK-NEXT: br label %preheader
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; CHECK-LABEL: preheader: ; preds = %entry
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; CHECK: br label %for
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; CHECK-LABEL: for: ; preds = %for, %preheader
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; CHECK br i1 %exitcond, label %exit, label %for
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; CHECK-LABEL: exit:
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; CHECK-NEXT: ret void
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entry:
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br label %preheader
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preheader:
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%idx.phi.trans = getelementptr inbounds [257 x i32], [257 x i32]* @p, i64 0, i64 1
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%.pre = load i32, i32* %idx.phi.trans, align 4
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br label %for
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for:
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%pre.phi = phi i32 [ %.pre, %preheader ], [ %pre.next, %for ]
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%iv = phi i64 [ 1, %preheader ], [ %iv.next, %for ]
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%add.1 = add i32 %pre.phi, %x
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%add.2 = add i32 %add.1, %x
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%idx.1 = getelementptr inbounds [257 x i32], [257 x i32]* @p, i64 0, i64 %iv
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%pre.next = load i32, i32* %idx.1, align 4
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%add.3 = add i32 %add.1, %pre.next
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%add.4 = add i32 %add.2, %add.3
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%idx.2 = getelementptr inbounds [257 x i32], [257 x i32]* @q, i64 0, i64 %iv
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store i32 %add.4, i32* %idx.2, align 4
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%iv.next = add nuw nsw i64 %iv, 1
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%exitcond = icmp eq i64 %iv.next, 2000
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br i1 %exitcond, label %exit, label %for
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exit:
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ret void
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}
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; FIXME: We can sink a store, if we can guarantee that it does not alias any
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; loads/stores in between.
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define void @cannot_sink_store(i32 %x, i32* %ptr, i64 %tc) {
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; CHECK-LABEL: define void @cannot_sink_store(
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; CHECK-NEXT: entry:
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; CHECK-NEXT: br label %preheader
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; CHECK-LABEL: preheader: ; preds = %entry
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; CHECK: br label %for
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; CHECK-LABEL: for: ; preds = %for, %preheader
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; CHECK br i1 %exitcond, label %exit, label %for
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; CHECK-LABEL: exit:
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; CHECK-NEXT: ret void
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;
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entry:
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br label %preheader
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preheader:
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%idx.phi.trans = getelementptr inbounds [257 x i32], [257 x i32]* @p, i64 0, i64 1
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%.pre = load i32, i32* %idx.phi.trans, align 4
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br label %for
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for:
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%pre.phi = phi i32 [ %.pre, %preheader ], [ %pre.next, %for ]
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%iv = phi i64 [ 1, %preheader ], [ %iv.next, %for ]
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%add.1 = add i32 %pre.phi, %x
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store i32 %add.1, i32* %ptr
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%idx.1 = getelementptr inbounds [257 x i32], [257 x i32]* @p, i64 0, i64 %iv
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%pre.next = load i32, i32* %idx.1, align 4
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%add.2 = add i32 %add.1, %pre.next
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%idx.2 = getelementptr inbounds [257 x i32], [257 x i32]* @q, i64 0, i64 %iv
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store i32 %add.2, i32* %idx.2, align 4
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%iv.next = add nuw nsw i64 %iv, 1
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%exitcond = icmp eq i64 %iv.next, 2000
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br i1 %exitcond, label %exit, label %for
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exit:
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ret void
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}
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; Some kinds of reductions are not detected by IVDescriptors. If we have a
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; cycle, we cannot sink it.
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define void @cannot_sink_reduction(i32 %x, i32* %ptr, i64 %tc) {
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; CHECK-LABEL: define void @cannot_sink_reduction(
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; CHECK-NEXT: entry:
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; CHECK-NEXT: br label %preheader
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; CHECK-LABEL: preheader: ; preds = %entry
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; CHECK: br label %for
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; CHECK-LABEL: for: ; preds = %for, %preheader
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; CHECK br i1 %exitcond, label %exit, label %for
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; CHECK-LABEL: exit: ; preds = %for
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; CHECK-NET: ret void
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;
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entry:
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br label %preheader
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preheader:
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%idx.phi.trans = getelementptr inbounds [257 x i32], [257 x i32]* @p, i64 0, i64 1
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%.pre = load i32, i32* %idx.phi.trans, align 4
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br label %for
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for:
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%pre.phi = phi i32 [ %.pre, %preheader ], [ %d, %for ]
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%iv = phi i64 [ 1, %preheader ], [ %iv.next, %for ]
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%d = sdiv i32 %pre.phi, %x
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%idx.1 = getelementptr inbounds [257 x i32], [257 x i32]* @p, i64 0, i64 %iv
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%pre.next = load i32, i32* %idx.1, align 4
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%add.2 = add i32 %x, %pre.next
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%idx.2 = getelementptr inbounds [257 x i32], [257 x i32]* @q, i64 0, i64 %iv
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store i32 %add.2, i32* %idx.2, align 4
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%iv.next = add nuw nsw i64 %iv, 1
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%exitcond = icmp eq i64 %iv.next, 2000
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br i1 %exitcond, label %exit, label %for
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exit:
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ret void
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}
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