MarkLiveEdge(BB, Succ);
};
- // Check if there is only one predecessor on 1st iteration. Note that because
- // we iterate in RPOT, we have already visited all its (non-latch)
- // predecessors.
- auto GetSolePredecessorOnFirstIteration = [&](BasicBlock * BB)->BasicBlock * {
+ // Check if there is only one value coming from all live predecessor blocks.
+ // Note that because we iterate in RPOT, we have already visited all its
+ // (non-latch) predecessors.
+ auto GetSoleInputOnFirstIteration = [&](PHINode & PN)->Value * {
+ BasicBlock *BB = PN.getParent();
if (BB == Header)
- return L->getLoopPredecessor();
- BasicBlock *OnlyPred = nullptr;
+ return PN.getIncomingValueForBlock(L->getLoopPredecessor());
+ Value *OnlyInput = nullptr;
for (auto *Pred : predecessors(BB))
- if (OnlyPred != Pred && LiveEdges.count({ Pred, BB })) {
- // 2 live preds.
- if (OnlyPred)
+ if (LiveEdges.count({ Pred, BB })) {
+ Value *Incoming = PN.getIncomingValueForBlock(Pred);
+ // Two inputs.
+ if (OnlyInput && OnlyInput != Incoming)
return nullptr;
- OnlyPred = Pred;
+ OnlyInput = Incoming;
}
- assert(OnlyPred && "No live predecessors?");
- return OnlyPred;
+ assert(OnlyInput && "No live predecessors?");
+ return OnlyInput;
};
DenseMap<Value *, Value *> FirstIterValue;
continue;
}
- // If this block has only one live pred, map its phis onto their SCEVs.
- if (auto *OnlyPred = GetSolePredecessorOnFirstIteration(BB))
- for (auto &PN : BB->phis()) {
- if (!PN.getType()->isIntegerTy())
- continue;
- auto *Incoming = PN.getIncomingValueForBlock(OnlyPred);
- if (DT.dominates(Incoming, BB->getTerminator())) {
- Value *FirstIterV =
- getValueOnFirstIteration(Incoming, FirstIterValue, SQ);
- FirstIterValue[&PN] = FirstIterV;
- }
+ // If Phi has only one input from all live input blocks, use it.
+ for (auto &PN : BB->phis()) {
+ if (!PN.getType()->isIntegerTy())
+ continue;
+ auto *Incoming = GetSoleInputOnFirstIteration(PN);
+ if (Incoming && DT.dominates(Incoming, BB->getTerminator())) {
+ Value *FirstIterV =
+ getValueOnFirstIteration(Incoming, FirstIterValue, SQ);
+ FirstIterValue[&PN] = FirstIterV;
}
+ }
using namespace PatternMatch;
ICmpInst::Predicate Pred;
unreachable
}
-; TODO: We can break the backedge here.
define i32 @test_multiple_pred_2() {
; CHECK-LABEL: @test_multiple_pred_2(
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[LOOP:%.*]]
; CHECK: loop:
-; CHECK-NEXT: [[SUM:%.*]] = phi i32 [ 0, [[ENTRY:%.*]] ], [ [[SUM_NEXT:%.*]], [[BACKEDGE:%.*]] ]
+; CHECK-NEXT: [[SUM:%.*]] = phi i32 [ 0, [[ENTRY:%.*]] ]
; CHECK-NEXT: [[SUB:%.*]] = sub i32 4, [[SUM]]
; CHECK-NEXT: [[IS_POSITIVE:%.*]] = icmp sgt i32 [[SUB]], 0
; CHECK-NEXT: br i1 [[IS_POSITIVE]], label [[IF_TRUE:%.*]], label [[IF_FALSE:%.*]]
; CHECK: if.true:
; CHECK-NEXT: br i1 undef, label [[IF_TRUE_1:%.*]], label [[IF_TRUE_2:%.*]]
; CHECK: if.true.1:
-; CHECK-NEXT: br label [[BACKEDGE]]
+; CHECK-NEXT: br label [[BACKEDGE:%.*]]
; CHECK: if.true.2:
; CHECK-NEXT: br label [[BACKEDGE]]
; CHECK: if.false:
; CHECK-NEXT: br label [[BACKEDGE]]
; CHECK: backedge:
; CHECK-NEXT: [[MERGE_PHI:%.*]] = phi i32 [ 0, [[IF_FALSE_1]] ], [ 0, [[IF_FALSE_2]] ], [ [[SUB]], [[IF_TRUE_1]] ], [ [[SUB]], [[IF_TRUE_2]] ]
-; CHECK-NEXT: [[SUM_NEXT]] = add i32 [[SUM]], [[MERGE_PHI]]
+; CHECK-NEXT: [[SUM_NEXT:%.*]] = add i32 [[SUM]], [[MERGE_PHI]]
; CHECK-NEXT: [[LOOP_COND:%.*]] = icmp ne i32 [[SUM_NEXT]], 4
-; CHECK-NEXT: br i1 [[LOOP_COND]], label [[LOOP]], label [[DONE:%.*]]
+; CHECK-NEXT: br i1 [[LOOP_COND]], label [[BACKEDGE_LOOP_CRIT_EDGE:%.*]], label [[DONE:%.*]]
+; CHECK: backedge.loop_crit_edge:
+; CHECK-NEXT: unreachable
; CHECK: done:
; CHECK-NEXT: [[SUM_NEXT_LCSSA:%.*]] = phi i32 [ [[SUM_NEXT]], [[BACKEDGE]] ]
; CHECK-NEXT: ret i32 [[SUM_NEXT_LCSSA]]