Implementation of asm-goto support in LLVM

This patch accompanies the RFC posted here:
http://lists.llvm.org/pipermail/llvm-dev/2018-October/127239.html

This patch adds a new CallBr IR instruction to support asm-goto
inline assembly like gcc as used by the linux kernel. This
instruction is both a call instruction and a terminator
instruction with multiple successors. Only inline assembly
usage is supported today.

This also adds a new INLINEASM_BR opcode to SelectionDAG and
MachineIR to represent an INLINEASM block that is also
considered a terminator instruction.

There will likely be more bug fixes and optimizations to follow
this, but we felt it had reached a point where we would like to
switch to an incremental development model.

Patch by Craig Topper, Alexander Ivchenko, Mikhail Dvoretckii

Differential Revision: https://reviews.llvm.org/D53765

llvm-svn: 353563
diff --git a/llvm/lib/Target/ARM/ARMISelDAGToDAG.cpp b/llvm/lib/Target/ARM/ARMISelDAGToDAG.cpp
index 648435a..f765334 100644
--- a/llvm/lib/Target/ARM/ARMISelDAGToDAG.cpp
+++ b/llvm/lib/Target/ARM/ARMISelDAGToDAG.cpp
@@ -2615,6 +2615,7 @@
       return;
     break;
   case ISD::INLINEASM:
+  case ISD::INLINEASM_BR:
     if (tryInlineAsm(N))
       return;
     break;
@@ -4319,7 +4320,7 @@
   if (!Changed)
     return false;
 
-  SDValue New = CurDAG->getNode(ISD::INLINEASM, SDLoc(N),
+  SDValue New = CurDAG->getNode(N->getOpcode(), SDLoc(N),
       CurDAG->getVTList(MVT::Other, MVT::Glue), AsmNodeOperands);
   New->setNodeId(-1);
   ReplaceNode(N, New.getNode());