[llvm] r300946 - [PartialInliner] Fix crash when inlining functions with unreachable blocks.

[Davide Italiano via llvm-commits]

Author: davide
Date: Thu Apr 20 23:25:00 2017
New Revision: 300946

URL: http://llvm.org/viewvc/llvm-project?rev=300946&view=rev
Log:
[PartialInliner] Fix crash when inlining functions with unreachable blocks.

CodeExtractor looks up the dominator node corresponding to return blocks
when splitting them. If one of these blocks is unreachable, there's no
node in the Dom and CodeExtractor crashes because it doesn't check
for domtree node validity.
In theory, we could add just a check for skipping null DTNodes in
`splitReturnBlock` but the fix I propose here is slightly different. To the
best of my knowledge, unreachable blocks are irrelevant for the algorithm,
therefore we can just skip them when building the candidate set in the
constructor.

Differential Revision:  https://reviews.llvm.org/D32335

Added:
    llvm/trunk/test/Transforms/CodeExtractor/unreachable-block.ll
Modified:
    llvm/trunk/lib/Transforms/Utils/CodeExtractor.cpp

Modified: llvm/trunk/lib/Transforms/Utils/CodeExtractor.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/CodeExtractor.cpp?rev=300946&r1=300945&r2=300946&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Utils/CodeExtractor.cpp (original)
+++ llvm/trunk/lib/Transforms/Utils/CodeExtractor.cpp Thu Apr 20 23:25:00 2017
@@ -74,24 +74,25 @@ bool CodeExtractor::isBlockValidForExtra
 
 /// \brief Build a set of blocks to extract if the input blocks are viable.
 static SetVector<BasicBlock *>
-buildExtractionBlockSet(ArrayRef<BasicBlock *> BBs) {
-  auto BBBegin = BBs.begin();
-  auto BBEnd = BBs.end();
-  assert(BBBegin != BBEnd && "The set of blocks to extract must be non-empty");
-
+buildExtractionBlockSet(ArrayRef<BasicBlock *> BBs, DominatorTree *DT) {
+  assert(!BBs.empty() && "The set of blocks to extract must be non-empty");
   SetVector<BasicBlock *> Result;
 
   // Loop over the blocks, adding them to our set-vector, and aborting with an
   // empty set if we encounter invalid blocks.
-  do {
-    if (!Result.insert(*BBBegin))
-      llvm_unreachable("Repeated basic blocks in extraction input");
+  for (BasicBlock *BB : BBs) {
 
-    if (!CodeExtractor::isBlockValidForExtraction(**BBBegin)) {
+    // If this block is dead, don't process it.
+    if (DT && !DT->isReachableFromEntry(BB))
+      continue;
+
+    if (!Result.insert(BB))
+      llvm_unreachable("Repeated basic blocks in extraction input");
+    if (!CodeExtractor::isBlockValidForExtraction(*BB)) {
       Result.clear();
       return Result;
     }
-  } while (++BBBegin != BBEnd);
+  }
 
 #ifndef NDEBUG
   for (SetVector<BasicBlock *>::iterator I = std::next(Result.begin()),
@@ -111,13 +112,13 @@ CodeExtractor::CodeExtractor(ArrayRef<Ba
                              bool AggregateArgs, BlockFrequencyInfo *BFI,
                              BranchProbabilityInfo *BPI)
     : DT(DT), AggregateArgs(AggregateArgs || AggregateArgsOpt), BFI(BFI),
-      BPI(BPI), Blocks(buildExtractionBlockSet(BBs)), NumExitBlocks(~0U) {}
+      BPI(BPI), Blocks(buildExtractionBlockSet(BBs, DT)), NumExitBlocks(~0U) {}
 
 CodeExtractor::CodeExtractor(DominatorTree &DT, Loop &L, bool AggregateArgs,
                              BlockFrequencyInfo *BFI,
                              BranchProbabilityInfo *BPI)
     : DT(&DT), AggregateArgs(AggregateArgs || AggregateArgsOpt), BFI(BFI),
-      BPI(BPI), Blocks(buildExtractionBlockSet(L.getBlocks())),
+      BPI(BPI), Blocks(buildExtractionBlockSet(L.getBlocks(), &DT)),
       NumExitBlocks(~0U) {}
 
 /// definedInRegion - Return true if the specified value is defined in the

Added: llvm/trunk/test/Transforms/CodeExtractor/unreachable-block.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/CodeExtractor/unreachable-block.ll?rev=300946&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/CodeExtractor/unreachable-block.ll (added)
+++ llvm/trunk/test/Transforms/CodeExtractor/unreachable-block.ll Thu Apr 20 23:25:00 2017
@@ -0,0 +1,38 @@
+; RUN: opt -S -partial-inliner %s | FileCheck %s
+
+; CHECK-LABEL: define void @dipsy(
+; CHECK-NEXT:   call void @tinkywinky.1_ontrue()
+; CHECK-NEXT:   call void @patatuccio()
+; CHECK-NEXT:   ret void
+; CHECK-NEXT: }
+
+; CHECK-LABEL: define internal void @tinkywinky.1_ontrue() {
+; CHECK-NEXT: newFuncRoot:
+; CHECK-NEXT:   br label %ontrue
+; CHECK: .exitStub:
+; CHECK-NEXT:   ret void
+; CHECK: ontrue:
+; CHECK-NEXT:   call void @patatino()
+; CHECK-NEXT:   br label %onfalse
+; CHECK: onfalse:
+; CHECK-NEXT:   br label %.exitStub
+; CHECK-NEXT: }
+
+declare void @patatino()
+declare void @patatuccio()
+
+define fastcc void @tinkywinky() {
+  br i1 true, label %ontrue, label %onfalse
+ontrue:
+  call void @patatino()
+  br label %onfalse
+onfalse:
+  call void @patatuccio()
+  ret void
+cantreachme:
+  ret void
+}
+define void @dipsy() {
+  call fastcc void @tinkywinky()
+  ret void
+}