[MemorySSA] Add all MemoryPhis before filling their values.

Summary:
Add all MemoryPhis in IDF before filling in their incomign values.
Otherwise, a new Phi can be added that needs to become the incoming
value of another Phi.
Test fails the verification in verifyPrevDefInPhis.

Reviewers: george.burgess.iv

Subscribers: jlebar, Prazek, zzheng, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D63353

llvm-svn: 363590

2 files changed, 64 insertions, 3 deletions

diff --git a/llvm/lib/Analysis/MemorySSAUpdater.cpp b/llvm/lib/Analysis/MemorySSAUpdater.cpp
index 9b82808681e..a9553e008d0 100644
--- a/llvm/lib/Analysis/MemorySSAUpdater.cpp
+++ b/llvm/lib/Analysis/MemorySSAUpdater.cpp
@@ -960,15 +960,25 @@ void MemorySSAUpdater::applyInsertUpdates(ArrayRef<CFGUpdate> Updates,
                                                  BlocksToProcess.end());
     IDFs.setDefiningBlocks(DefiningBlocks);
     IDFs.calculate(IDFBlocks);
+
+    SmallSetVector<MemoryPhi *, 4> PhisToFill;
+    // First create all needed Phis.
+    for (auto *BBIDF : IDFBlocks)
+      if (!MSSA->getMemoryAccess(BBIDF)) {
+        auto *IDFPhi = MSSA->createMemoryPhi(BBIDF);
+        InsertedPhis.push_back(IDFPhi);
+        PhisToFill.insert(IDFPhi);
+      }
+    // Then update or insert their correct incoming values.
     for (auto *BBIDF : IDFBlocks) {
-      if (auto *IDFPhi = MSSA->getMemoryAccess(BBIDF)) {
+      auto *IDFPhi = MSSA->getMemoryAccess(BBIDF);
+      assert(IDFPhi && "Phi must exist");
+      if (!PhisToFill.count(IDFPhi)) {
         // Update existing Phi.
         // FIXME: some updates may be redundant, try to optimize and skip some.
         for (unsigned I = 0, E = IDFPhi->getNumIncomingValues(); I < E; ++I)
           IDFPhi->setIncomingValue(I, GetLastDef(IDFPhi->getIncomingBlock(I)));
       } else {
-        IDFPhi = MSSA->createMemoryPhi(BBIDF);
-        InsertedPhis.push_back(IDFPhi);
         for (auto &Pair : children<GraphDiffInvBBPair>({GD, BBIDF})) {
           BasicBlock *Pi = Pair.second;
           IDFPhi->addIncoming(GetLastDef(Pi), Pi);
diff --git a/llvm/test/Analysis/MemorySSA/update_unroll.ll b/llvm/test/Analysis/MemorySSA/update_unroll.ll
new file mode 100644
index 00000000000..5fa4eacc119
--- /dev/null
+++ b/llvm/test/Analysis/MemorySSA/update_unroll.ll
@@ -0,0 +1,51 @@
+; RUN: opt -enable-mssa-loop-dependency -verify-memoryssa  -loop-rotate -S %s | FileCheck %s
+; REQUIRES: asserts
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-grtev4-linux-gnu"
+
+; Check verification passes after loop rotate, when adding phis in blocks
+; receiving incoming edges and adding phis in IDF blocks.
+; CHECK-LABEL: @f
+define void @f() align 32 {
+entry:
+  br label %while.cond.outer
+
+while.cond80.while.cond.loopexit_crit_edge:       ; preds = %if.else99
+  br label %while.cond.outer
+
+while.cond.outer:                                 ; preds = %while.cond80.while.cond.loopexit_crit_edge, %entry
+  br i1 undef, label %while.cond.outer.return.loopexit2_crit_edge, label %while.body.lr.ph
+
+while.body.lr.ph:                                 ; preds = %while.cond.outer
+  br label %while.body
+
+while.body:                                       ; preds = %while.body.lr.ph
+  br i1 undef, label %if.then42, label %if.end61
+
+if.then42:                                        ; preds = %while.body
+  br label %return.loopexit2
+
+if.end61:                                         ; preds = %while.body
+  br label %while.body82
+
+while.body82:                                     ; preds = %if.end61
+  br i1 undef, label %return.loopexit, label %if.else99
+
+if.else99:                                        ; preds = %while.body82
+  store i32 0, i32* inttoptr (i64 44 to i32*), align 4
+  br label %while.cond80.while.cond.loopexit_crit_edge
+
+return.loopexit:                                  ; preds = %while.body82
+  br label %return
+
+while.cond.outer.return.loopexit2_crit_edge:      ; preds = %while.cond.outer
+  br label %return.loopexit2
+
+return.loopexit2:                                 ; preds = %while.cond.outer.return.loopexit2_crit_edge, %if.then42
+  br label %return
+
+return:                                           ; preds = %return.loopexit2, %return.loopexit
+  ret void
+}
+