CodeGenSchedule: smallvector.push_back(smallvector[0]) is dangerous

The element passed to push_back is not copied before the vector reallocates.
The client needs to copy the element first before passing it to push_back.

No test case, will be tested by follow-up swift scheduler model change (it
segfaults without this change).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@183459 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/utils/TableGen/CodeGenSchedule.cpp b/utils/TableGen/CodeGenSchedule.cpp
index f2af7edbb2efa54a1ffbca8909775424b2fad4c5..53b72d03b5b4f898236b1161833516f5094056bd 100644 (file)
--- a/utils/TableGen/CodeGenSchedule.cpp
+++ b/utils/TableGen/CodeGenSchedule.cpp
@@ -1172,7 +1172,9 @@ pushVariant(const TransVariant &VInfo, bool IsRead) {
     unsigned OperIdx = RWSequences.size()-1;
     // Make N-1 copies of this transition's last sequence.
     for (unsigned i = 1, e = SelectedRWs.size(); i != e; ++i) {
-      RWSequences.push_back(RWSequences[OperIdx]);
+      // Create a temporary copy the vector could reallocate.
+      SmallVector<unsigned, 4> Tmp = RWSequences[OperIdx];
+      RWSequences.push_back(Tmp);
     }
     // Push each of the N elements of the SelectedRWs onto a copy of the last
     // sequence (split the current operand into N operands).