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

1 files changed, 2 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/Utils/BasicBlockUtils.cpp b/llvm/lib/Transforms/Utils/BasicBlockUtils.cpp
index 41ad4fefe1f..2410f652fd7 100644
--- a/llvm/lib/Transforms/Utils/BasicBlockUtils.cpp
+++ b/llvm/lib/Transforms/Utils/BasicBlockUtils.cpp
@@ -549,6 +549,8 @@ BasicBlock *llvm::SplitBlockPredecessors(BasicBlock *BB,
     // all BlockAddress uses would need to be updated.
     assert(!isa<IndirectBrInst>(Preds[i]->getTerminator()) &&
            "Cannot split an edge from an IndirectBrInst");
+    assert(!isa<CallBrInst>(Preds[i]->getTerminator()) &&
+           "Cannot split an edge from a CallBrInst");
     Preds[i]->getTerminator()->replaceUsesOfWith(BB, NewBB);
   }