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, 45 insertions, 0 deletions

diff --git a/llvm/lib/IR/AsmWriter.cpp b/llvm/lib/IR/AsmWriter.cpp
index 980de9ab1ee..af3db5186a2 100644
--- a/llvm/lib/IR/AsmWriter.cpp
+++ b/llvm/lib/IR/AsmWriter.cpp
@@ -3836,6 +3836,51 @@ void AssemblyWriter::printInstruction(const Instruction &I) {
     writeOperand(II->getNormalDest(), true);
     Out << " unwind ";
     writeOperand(II->getUnwindDest(), true);
+  } else if (const CallBrInst *CBI = dyn_cast<CallBrInst>(&I)) {
+    Operand = CBI->getCalledValue();
+    FunctionType *FTy = CBI->getFunctionType();
+    Type *RetTy = FTy->getReturnType();
+    const AttributeList &PAL = CBI->getAttributes();
+
+    // Print the calling convention being used.
+    if (CBI->getCallingConv() != CallingConv::C) {
+      Out << " ";
+      PrintCallingConv(CBI->getCallingConv(), Out);
+    }
+
+    if (PAL.hasAttributes(AttributeList::ReturnIndex))
+      Out << ' ' << PAL.getAsString(AttributeList::ReturnIndex);
+
+    // If possible, print out the short form of the callbr instruction. We can
+    // only do this if the first argument is a pointer to a nonvararg function,
+    // and if the return type is not a pointer to a function.
+    //
+    Out << ' ';
+    TypePrinter.print(FTy->isVarArg() ? FTy : RetTy, Out);
+    Out << ' ';
+    writeOperand(Operand, false);
+    Out << '(';
+    for (unsigned op = 0, Eop = CBI->getNumArgOperands(); op < Eop; ++op) {
+      if (op)
+        Out << ", ";
+      writeParamOperand(CBI->getArgOperand(op), PAL.getParamAttributes(op));
+    }
+
+    Out << ')';
+    if (PAL.hasAttributes(AttributeList::FunctionIndex))
+      Out << " #" << Machine.getAttributeGroupSlot(PAL.getFnAttributes());
+
+    writeOperandBundles(CBI);
+
+    Out << "\n          to ";
+    writeOperand(CBI->getDefaultDest(), true);
+    Out << " [";
+    for (unsigned i = 0, e = CBI->getNumIndirectDests(); i != e; ++i) {
+      if (i != 0)
+        Out << ", ";
+      writeOperand(CBI->getIndirectDest(i), true);
+    }
+    Out << ']';
   } else if (const AllocaInst *AI = dyn_cast<AllocaInst>(&I)) {
     Out << ' ';
     if (AI->isUsedWithInAlloca())