ARM: correctly update CFG when splitting BB to fix branch.

Because the block-splitting code is multi-purpose, we have to meddle with the
branches when using it to fixup a conditional branch destination. We got the
code right, but forgot to update the CFG so the verifier complained when
expensive checks were on.

Probably harmless since constant-islands comes so late, but best to fix it
anyway.

llvm-svn: 318148

1 files changed, 6 insertions, 0 deletions

diff --git a/llvm/lib/Target/ARM/ARMConstantIslandPass.cpp b/llvm/lib/Target/ARM/ARMConstantIslandPass.cpp
index 79356d70b62..e318a862405 100644
--- a/llvm/lib/Target/ARM/ARMConstantIslandPass.cpp
+++ b/llvm/lib/Target/ARM/ARMConstantIslandPass.cpp
@@ -1689,6 +1689,12 @@ ARMConstantIslands::fixupConditionalBr(ImmBranch &Br) {
     int delta = TII->getInstSizeInBytes(MBB->back());
     BBInfo[MBB->getNumber()].Size -= delta;
     MBB->back().eraseFromParent();
+
+    // The conditional successor will be swapped between the BBs after this, so
+    // update CFG.
+    MBB->addSuccessor(DestBB);
+    std::next(MBB->getIterator())->removeSuccessor(DestBB);
+
     // BBInfo[SplitBB].Offset is wrong temporarily, fixed below
   }
   MachineBasicBlock *NextBB = &*++MBB->getIterator();