[MemorySSA] Fix for non-determinism in codegen

This patch fixes the non-determinism caused due to iterating SmallPtrSet's
which was uncovered due to the experimental "reverse iteration order " patch:
https://reviews.llvm.org/D26718

The following unit tests failed because of the undefined order of iteration.
LLVM :: Transforms/Util/MemorySSA/cyclicphi.ll
LLVM :: Transforms/Util/MemorySSA/many-dom-backedge.ll
LLVM :: Transforms/Util/MemorySSA/many-doms.ll
LLVM :: Transforms/Util/MemorySSA/phi-translation.ll

Reviewers: dberlin, mgrang

Subscribers: dberlin, llvm-commits, david2050

Differential Revision: https://reviews.llvm.org/D26704

llvm-svn: 287563

diff --git a/llvm/include/llvm/Transforms/Utils/MemorySSA.h b/llvm/include/llvm/Transforms/Utils/MemorySSA.h
index b0db0af..f377791 100644 (file)
--- a/llvm/include/llvm/Transforms/Utils/MemorySSA.h
+++ b/llvm/include/llvm/Transforms/Utils/MemorySSA.h
@@ -629,7 +629,8 @@ private:
   MemoryAccess *findDominatingDef(BasicBlock *, enum InsertionPlace);
   void removeFromLookups(MemoryAccess *);
 
-  void placePHINodes(const SmallPtrSetImpl<BasicBlock *> &);
+  void placePHINodes(const SmallPtrSetImpl<BasicBlock *> &,
+                     const DenseMap<const BasicBlock *, unsigned int> &);
   MemoryAccess *renameBlock(BasicBlock *, MemoryAccess *);
   void renamePass(DomTreeNode *, MemoryAccess *IncomingVal,
                   SmallPtrSet<BasicBlock *, 16> &Visited);

diff --git a/llvm/lib/Transforms/Utils/MemorySSA.cpp b/llvm/lib/Transforms/Utils/MemorySSA.cpp
index 58a8c88..1cf5ef0 100644 (file)
--- a/llvm/lib/Transforms/Utils/MemorySSA.cpp
+++ b/llvm/lib/Transforms/Utils/MemorySSA.cpp
@@ -1463,13 +1463,19 @@ void MemorySSA::OptimizeUses::optimizeUses() {
 }
 
 void MemorySSA::placePHINodes(
-    const SmallPtrSetImpl<BasicBlock *> &DefiningBlocks) {
+    const SmallPtrSetImpl<BasicBlock *> &DefiningBlocks,
+    const DenseMap<const BasicBlock *, unsigned int> &BBNumbers) {
   // Determine where our MemoryPhi's should go
   ForwardIDFCalculator IDFs(*DT);
   IDFs.setDefiningBlocks(DefiningBlocks);
   SmallVector<BasicBlock *, 32> IDFBlocks;
   IDFs.calculate(IDFBlocks);
 
+  std::sort(IDFBlocks.begin(), IDFBlocks.end(),
+            [&BBNumbers](const BasicBlock *A, const BasicBlock *B) {
+              return BBNumbers.lookup(A) < BBNumbers.lookup(B);
+            });
+
   // Now place MemoryPhi nodes.
   for (auto &BB : IDFBlocks) {
     // Insert phi node
@@ -1491,6 +1497,8 @@ void MemorySSA::buildMemorySSA() {
   BasicBlock &StartingPoint = F.getEntryBlock();
   LiveOnEntryDef = make_unique<MemoryDef>(F.getContext(), nullptr, nullptr,
                                           &StartingPoint, NextID++);
+  DenseMap<const BasicBlock *, unsigned int> BBNumbers;
+  unsigned NextBBNum = 0;
 
   // We maintain lists of memory accesses per-block, trading memory for time. We
   // could just look up the memory access for every possible instruction in the
@@ -1500,6 +1508,7 @@ void MemorySSA::buildMemorySSA() {
   // Go through each block, figure out where defs occur, and chain together all
   // the accesses.
   for (BasicBlock &B : F) {
+    BBNumbers[&B] = NextBBNum++;
     bool InsertIntoDef = false;
     AccessList *Accesses = nullptr;
     for (Instruction &I : B) {
@@ -1517,7 +1526,7 @@ void MemorySSA::buildMemorySSA() {
     if (Accesses)
       DefUseBlocks.insert(&B);
   }
-  placePHINodes(DefiningBlocks);
+  placePHINodes(DefiningBlocks, BBNumbers);
 
   // Now do regular SSA renaming on the MemoryDef/MemoryUse. Visited will get
   // filled in with all blocks.

diff --git a/llvm/test/Transforms/Util/MemorySSA/cyclicphi.ll b/llvm/test/Transforms/Util/MemorySSA/cyclicphi.ll
index 9c29784..6e91db9 100644 (file)
--- a/llvm/test/Transforms/Util/MemorySSA/cyclicphi.ll
+++ b/llvm/test/Transforms/Util/MemorySSA/cyclicphi.ll
@@ -11,7 +11,7 @@ define hidden void @quux(%struct.hoge *%f) align 2 {
   br label %bb26
 
 bb26:                                             ; preds = %bb77, %0
-; CHECK:  3 = MemoryPhi({%0,liveOnEntry},{bb77,2})
+; CHECK:  2 = MemoryPhi({%0,liveOnEntry},{bb77,3})
 ; CHECK-NEXT:   br i1 undef, label %bb68, label %bb77
   br i1 undef, label %bb68, label %bb77
 
@@ -19,14 +19,14 @@ bb68:                                             ; preds = %bb26
 ; CHECK:  MemoryUse(liveOnEntry)
 ; CHECK-NEXT:   %tmp69 = load i64, i64* null, align 8
   %tmp69 = load i64, i64* null, align 8
-; CHECK:  1 = MemoryDef(3)
+; CHECK:  1 = MemoryDef(2)
 ; CHECK-NEXT:   store i64 %tmp69, i64* %tmp, align 8
   store i64 %tmp69, i64* %tmp, align 8
   br label %bb77
 
 bb77:                                             ; preds = %bb68, %bb26
-; CHECK:  2 = MemoryPhi({bb26,3},{bb68,1})
-; CHECK:  MemoryUse(2)
+; CHECK:  3 = MemoryPhi({bb26,2},{bb68,1})
+; CHECK:  MemoryUse(3)
 ; CHECK-NEXT:   %tmp78 = load i64*, i64** %tmp25, align 8
   %tmp78 = load i64*, i64** %tmp25, align 8
   %tmp79 = getelementptr inbounds i64, i64* %tmp78, i64 undef
@@ -41,21 +41,21 @@ define void @quux_skip(%struct.hoge* noalias %f, i64* noalias %g) align 2 {
   br label %bb26
 
 bb26:                                             ; preds = %bb77, %0
-; CHECK: 3 = MemoryPhi({%0,liveOnEntry},{bb77,2})
+; CHECK: 2 = MemoryPhi({%0,liveOnEntry},{bb77,3})
 ; CHECK-NEXT: br i1 undef, label %bb68, label %bb77
   br i1 undef, label %bb68, label %bb77
 
 bb68:                                             ; preds = %bb26
-; CHECK: MemoryUse(3)
+; CHECK: MemoryUse(2)
 ; CHECK-NEXT: %tmp69 = load i64, i64* %g, align 8
   %tmp69 = load i64, i64* %g, align 8
-; CHECK: 1 = MemoryDef(3)
+; CHECK: 1 = MemoryDef(2)
 ; CHECK-NEXT: store i64 %tmp69, i64* %g, align 8
   store i64 %tmp69, i64* %g, align 8
   br label %bb77
 
 bb77:                                             ; preds = %bb68, %bb26
-; CHECK: 2 = MemoryPhi({bb26,3},{bb68,1})
+; CHECK: 3 = MemoryPhi({bb26,2},{bb68,1})
 ; CHECK: MemoryUse(liveOnEntry)
 ; CHECK-NEXT: %tmp78 = load i64*, i64** %tmp25, align 8
   %tmp78 = load i64*, i64** %tmp25, align 8
@@ -70,24 +70,24 @@ define void @quux_dominated(%struct.hoge* noalias %f, i64* noalias %g) align 2 {
   br label %bb26
 
 bb26:                                             ; preds = %bb77, %0
-; CHECK: 4 = MemoryPhi({%0,liveOnEntry},{bb77,2})
-; CHECK: MemoryUse(4)
+; CHECK: 3 = MemoryPhi({%0,liveOnEntry},{bb77,2})
+; CHECK: MemoryUse(3)
 ; CHECK-NEXT: load i64*, i64** %tmp25, align 8
   load i64*, i64** %tmp25, align 8
   br i1 undef, label %bb68, label %bb77
 
 bb68:                                             ; preds = %bb26
-; CHECK: MemoryUse(4)
+; CHECK: MemoryUse(3)
 ; CHECK-NEXT: %tmp69 = load i64, i64* %g, align 8
   %tmp69 = load i64, i64* %g, align 8
-; CHECK: 1 = MemoryDef(4)
+; CHECK: 1 = MemoryDef(3)
 ; CHECK-NEXT: store i64 %tmp69, i64* %g, align 8
   store i64 %tmp69, i64* %g, align 8
   br label %bb77
 
 bb77:                                             ; preds = %bb68, %bb26
-; CHECK: 3 = MemoryPhi({bb26,4},{bb68,1})
-; CHECK: 2 = MemoryDef(3)
+; CHECK: 4 = MemoryPhi({bb26,3},{bb68,1})
+; CHECK: 2 = MemoryDef(4)
 ; CHECK-NEXT: store i64* null, i64** %tmp25, align 8
   store i64* null, i64** %tmp25, align 8
   br label %bb26
@@ -101,23 +101,23 @@ define void @quux_nodominate(%struct.hoge* noalias %f, i64* noalias %g) align 2
   br label %bb26
 
 bb26:                                             ; preds = %bb77, %0
-; CHECK: 3 = MemoryPhi({%0,liveOnEntry},{bb77,2})
+; CHECK: 2 = MemoryPhi({%0,liveOnEntry},{bb77,3})
 ; CHECK: MemoryUse(liveOnEntry)
 ; CHECK-NEXT: load i64*, i64** %tmp25, align 8
   load i64*, i64** %tmp25, align 8
   br i1 undef, label %bb68, label %bb77
 
 bb68:                                             ; preds = %bb26
-; CHECK: MemoryUse(3)
+; CHECK: MemoryUse(2)
 ; CHECK-NEXT: %tmp69 = load i64, i64* %g, align 8
   %tmp69 = load i64, i64* %g, align 8
-; CHECK: 1 = MemoryDef(3)
+; CHECK: 1 = MemoryDef(2)
 ; CHECK-NEXT: store i64 %tmp69, i64* %g, align 8
   store i64 %tmp69, i64* %g, align 8
   br label %bb77
 
 bb77:                                             ; preds = %bb68, %bb26
-; CHECK: 2 = MemoryPhi({bb26,3},{bb68,1})
+; CHECK: 3 = MemoryPhi({bb26,2},{bb68,1})
 ; CHECK-NEXT: br label %bb26
   br label %bb26
 }

diff --git a/llvm/test/Transforms/Util/MemorySSA/many-dom-backedge.ll b/llvm/test/Transforms/Util/MemorySSA/many-dom-backedge.ll
index 3d76f4a..c2216a4 100644 (file)
--- a/llvm/test/Transforms/Util/MemorySSA/many-dom-backedge.ll
+++ b/llvm/test/Transforms/Util/MemorySSA/many-dom-backedge.ll
@@ -11,7 +11,7 @@ entry:
   br label %loopbegin
 
 loopbegin:
-; CHECK: 9 = MemoryPhi({entry,liveOnEntry},{sw.epilog,6})
+; CHECK: 8 = MemoryPhi({entry,liveOnEntry},{sw.epilog,6})
 ; CHECK-NEXT: %n =
   %n = phi i32 [ 0, %entry ], [ %1, %sw.epilog ]
   %m = alloca i32, align 4
@@ -23,42 +23,42 @@ loopbegin:
   ]
 
 sw.bb:
-; CHECK: 1 = MemoryDef(9)
+; CHECK: 1 = MemoryDef(8)
 ; CHECK-NEXT: store i32 1
   store i32 1, i32* %m, align 4
   br label %sw.epilog
 
 sw.bb1:
-; CHECK: 2 = MemoryDef(9)
+; CHECK: 2 = MemoryDef(8)
 ; CHECK-NEXT: store i32 2
   store i32 2, i32* %m, align 4
   br label %sw.epilog
 
 sw.bb2:
-; CHECK: 3 = MemoryDef(9)
+; CHECK: 3 = MemoryDef(8)
 ; CHECK-NEXT: store i32 3
   store i32 3, i32* %m, align 4
   br label %sw.epilog
 
 sw.bb3:
-; CHECK: 10 = MemoryPhi({loopbegin,9},{sw.almostexit,6})
-; CHECK: 4 = MemoryDef(10)
+; CHECK: 9 = MemoryPhi({loopbegin,8},{sw.almostexit,6})
+; CHECK: 4 = MemoryDef(9)
 ; CHECK-NEXT: store i32 4
   store i32 4, i32* %m, align 4
   br label %sw.epilog
 
 sw.default:
-; CHECK: 5 = MemoryDef(9)
+; CHECK: 5 = MemoryDef(8)
 ; CHECK-NEXT: store i32 5
   store i32 5, i32* %m, align 4
   br label %sw.epilog
 
 sw.epilog:
-; CHECK: 8 = MemoryPhi({sw.default,5},{sw.bb3,4},{sw.bb,1},{sw.bb1,2},{sw.bb2,3})
-; CHECK-NEXT: MemoryUse(8)
+; CHECK: 10 = MemoryPhi({sw.default,5},{sw.bb3,4},{sw.bb,1},{sw.bb1,2},{sw.bb2,3})
+; CHECK-NEXT: MemoryUse(10)
 ; CHECK-NEXT: %0 =
   %0 = load i32, i32* %m, align 4
-; CHECK: 6 = MemoryDef(8)
+; CHECK: 6 = MemoryDef(10)
 ; CHECK-NEXT: %1 =
   %1 = load volatile i32, i32* %p, align 4
   %2 = icmp eq i32 %0, %1

diff --git a/llvm/test/Transforms/Util/MemorySSA/many-doms.ll b/llvm/test/Transforms/Util/MemorySSA/many-doms.ll
index d2e6c6f..1f57cbf 100644 (file)
--- a/llvm/test/Transforms/Util/MemorySSA/many-doms.ll
+++ b/llvm/test/Transforms/Util/MemorySSA/many-doms.ll
@@ -10,7 +10,7 @@ entry:
   br label %loopbegin
 
 loopbegin:
-; CHECK: 8 = MemoryPhi({entry,liveOnEntry},{sw.epilog,6})
+; CHECK: 7 = MemoryPhi({entry,liveOnEntry},{sw.epilog,6})
 ; CHECK-NEXT: %n =
   %n = phi i32 [ 0, %entry ], [ %1, %sw.epilog ]
   %m = alloca i32, align 4
@@ -22,41 +22,41 @@ loopbegin:
   ]
 
 sw.bb:
-; CHECK: 1 = MemoryDef(8)
+; CHECK: 1 = MemoryDef(7)
 ; CHECK-NEXT: store i32 1
   store i32 1, i32* %m, align 4
   br label %sw.epilog
 
 sw.bb1:
-; CHECK: 2 = MemoryDef(8)
+; CHECK: 2 = MemoryDef(7)
 ; CHECK-NEXT: store i32 2
   store i32 2, i32* %m, align 4
   br label %sw.epilog
 
 sw.bb2:
-; CHECK: 3 = MemoryDef(8)
+; CHECK: 3 = MemoryDef(7)
 ; CHECK-NEXT: store i32 3
   store i32 3, i32* %m, align 4
   br label %sw.epilog
 
 sw.bb3:
-; CHECK: 4 = MemoryDef(8)
+; CHECK: 4 = MemoryDef(7)
 ; CHECK-NEXT: store i32 4
   store i32 4, i32* %m, align 4
   br label %sw.epilog
 
 sw.default:
-; CHECK: 5 = MemoryDef(8)
+; CHECK: 5 = MemoryDef(7)
 ; CHECK-NEXT: store i32 5
   store i32 5, i32* %m, align 4
   br label %sw.epilog
 
 sw.epilog:
-; CHECK: 7 = MemoryPhi({sw.default,5},{sw.bb,1},{sw.bb1,2},{sw.bb2,3},{sw.bb3,4})
-; CHECK-NEXT: MemoryUse(7)
+; CHECK: 8 = MemoryPhi({sw.default,5},{sw.bb,1},{sw.bb1,2},{sw.bb2,3},{sw.bb3,4})
+; CHECK-NEXT: MemoryUse(8)
 ; CHECK-NEXT: %0 =
   %0 = load i32, i32* %m, align 4
-; CHECK: 6 = MemoryDef(7)
+; CHECK: 6 = MemoryDef(8)
 ; CHECK-NEXT: %1 =
   %1 = load volatile i32, i32* %p, align 4
   %2 = icmp eq i32 %0, %1

diff --git a/llvm/test/Transforms/Util/MemorySSA/phi-translation.ll b/llvm/test/Transforms/Util/MemorySSA/phi-translation.ll
index 42959f9..c91faf2 100644 (file)
--- a/llvm/test/Transforms/Util/MemorySSA/phi-translation.ll
+++ b/llvm/test/Transforms/Util/MemorySSA/phi-translation.ll
@@ -45,15 +45,15 @@ if.then:
   br i1 %val2, label %phi.2, label %phi.3
 
 phi.3:
-; CHECK: 6 = MemoryPhi({entry,1},{if.then,2})
-; CHECK: 3 = MemoryDef(6)
+; CHECK: 5 = MemoryPhi({entry,1},{if.then,2})
+; CHECK: 3 = MemoryDef(5)
 ; CHECK-NEXT: store i8 3, i8* %local2
   store i8 3, i8* %local2
   br i1 %val3, label %phi.2, label %phi.1
 
 phi.2:
-; CHECK: 5 = MemoryPhi({if.then,2},{phi.3,3})
-; CHECK: 4 = MemoryDef(5)
+; CHECK: 6 = MemoryPhi({if.then,2},{phi.3,3})
+; CHECK: 4 = MemoryDef(6)
 ; CHECK-NEXT: store i8 4, i8* %local2
   store i8 4, i8* %local2
   br label %phi.1
@@ -120,8 +120,8 @@ define void @looped(i8* noalias %p1, i8* noalias %p2) {
   br label %loop.1
 
 loop.1:
-; CHECK: 7 = MemoryPhi({%0,1},{loop.3,4})
-; CHECK: 2 = MemoryDef(7)
+; CHECK: 5 = MemoryPhi({%0,1},{loop.3,4})
+; CHECK: 2 = MemoryDef(5)
 ; CHECK-NEXT: store i8 0, i8* %p2
   store i8 0, i8* %p2
   br i1 undef, label %loop.2, label %loop.3
@@ -134,8 +134,8 @@ loop.2:
   br label %loop.3
 
 loop.3:
-; CHECK: 5 = MemoryPhi({loop.1,2},{loop.2,3})
-; CHECK: 4 = MemoryDef(5)
+; CHECK: 7 = MemoryPhi({loop.1,2},{loop.2,3})
+; CHECK: 4 = MemoryDef(7)
 ; CHECK-NEXT: store i8 2, i8* %p2
   store i8 2, i8* %p2
 ; CHECK: MemoryUse(1)
@@ -149,12 +149,12 @@ define void @looped_visitedonlyonce(i8* noalias %p1, i8* noalias %p2) {
   br label %while.cond
 
 while.cond:
-; CHECK: 5 = MemoryPhi({%0,liveOnEntry},{if.end,3})
+; CHECK: 4 = MemoryPhi({%0,liveOnEntry},{if.end,3})
 ; CHECK-NEXT: br i1 undef, label %if.then, label %if.end
   br i1 undef, label %if.then, label %if.end
 
 if.then:
-; CHECK: 1 = MemoryDef(5)
+; CHECK: 1 = MemoryDef(4)
 ; CHECK-NEXT: store i8 0, i8* %p1
   store i8 0, i8* %p1
   br i1 undef, label %if.end, label %if.then2
@@ -166,14 +166,14 @@ if.then2:
   br label %if.end
 
 if.end:
-; CHECK: 4 = MemoryPhi({while.cond,5},{if.then,1},{if.then2,2})
-; CHECK: MemoryUse(4)
+; CHECK: 5 = MemoryPhi({while.cond,4},{if.then,1},{if.then2,2})
+; CHECK: MemoryUse(5)
 ; CHECK-NEXT: load i8, i8* %p1
   load i8, i8* %p1
-; CHECK: 3 = MemoryDef(4)
+; CHECK: 3 = MemoryDef(5)
 ; CHECK-NEXT: store i8 2, i8* %p2
   store i8 2, i8* %p2
-; CHECK: MemoryUse(4)
+; CHECK: MemoryUse(5)
 ; CHECK-NEXT: load i8, i8* %p1
   load i8, i8* %p1
   br label %while.cond