FastIsel: take care to update iterators when removing instructions.

We keep a few iterators into the basic block we're selecting while
performing FastISel. Usually this is fine, but occasionally code wants
to remove already-emitted instructions. When this happens we have to be
careful to update those iterators so they're not pointint at dangling
memory.

llvm-svn: 349365

1 files changed, 9 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/FastISel.cpp b/llvm/lib/CodeGen/SelectionDAG/FastISel.cpp
index d5f066c2423..a9a3c44ea0c 100644
--- a/llvm/lib/CodeGen/SelectionDAG/FastISel.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/FastISel.cpp
@@ -547,6 +547,15 @@ void FastISel::removeDeadCode(MachineBasicBlock::iterator I,
   assert(I.isValid() && E.isValid() && std::distance(I, E) > 0 &&
          "Invalid iterator!");
   while (I != E) {
+    if (LastFlushPoint == I)
+      LastFlushPoint = E;
+    if (SavedInsertPt == I)
+      SavedInsertPt = E;
+    if (EmitStartPt == I)
+      EmitStartPt = E.isValid() ? &*E : nullptr;
+    if (LastLocalValue == I)
+      LastLocalValue = E.isValid() ? &*E : nullptr;
+
     MachineInstr *Dead = &*I;
     ++I;
     Dead->eraseFromParent();