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

4 files changed, 130 insertions, 0 deletions

diff --git a/llvm/lib/AsmParser/LLLexer.cpp b/llvm/lib/AsmParser/LLLexer.cpp
index b543115a88e..461117c92b8 100644
--- a/llvm/lib/AsmParser/LLLexer.cpp
+++ b/llvm/lib/AsmParser/LLLexer.cpp
@@ -858,6 +858,7 @@ lltok::Kind LLLexer::LexIdentifier() {
   INSTKEYWORD(invoke,      Invoke);
   INSTKEYWORD(resume,      Resume);
   INSTKEYWORD(unreachable, Unreachable);
+  INSTKEYWORD(callbr,      CallBr);
 
   INSTKEYWORD(alloca,      Alloca);
   INSTKEYWORD(load,        Load);
diff --git a/llvm/lib/AsmParser/LLParser.cpp b/llvm/lib/AsmParser/LLParser.cpp
index 855c5d26500..2a36bb18984 100644
--- a/llvm/lib/AsmParser/LLParser.cpp
+++ b/llvm/lib/AsmParser/LLParser.cpp
@@ -163,6 +163,14 @@ bool LLParser::ValidateEndOfModule() {
       AS = AS.addAttributes(Context, AttributeList::FunctionIndex,
                             AttributeSet::get(Context, FnAttrs));
       II->setAttributes(AS);
+    } else if (CallBrInst *CBI = dyn_cast<CallBrInst>(V)) {
+      AttributeList AS = CBI->getAttributes();
+      AttrBuilder FnAttrs(AS.getFnAttributes());
+      AS = AS.removeAttributes(Context, AttributeList::FunctionIndex);
+      FnAttrs.merge(B);
+      AS = AS.addAttributes(Context, AttributeList::FunctionIndex,
+                            AttributeSet::get(Context, FnAttrs));
+      CBI->setAttributes(AS);
     } else if (auto *GV = dyn_cast<GlobalVariable>(V)) {
       AttrBuilder Attrs(GV->getAttributes());
       Attrs.merge(B);
@@ -5566,6 +5574,7 @@ int LLParser::ParseInstruction(Instruction *&Inst, BasicBlock *BB,
   case lltok::kw_catchswitch: return ParseCatchSwitch(Inst, PFS);
   case lltok::kw_catchpad:    return ParseCatchPad(Inst, PFS);
   case lltok::kw_cleanuppad:  return ParseCleanupPad(Inst, PFS);
+  case lltok::kw_callbr:      return ParseCallBr(Inst, PFS);
   // Unary Operators.
   case lltok::kw_fneg: {
     FastMathFlags FMF = EatFastMathFlagsIfPresent();
@@ -6184,6 +6193,124 @@ bool LLParser::ParseUnaryOp(Instruction *&Inst, PerFunctionState &PFS,
   return false;
 }
 
+/// ParseCallBr
+///   ::= 'callbr' OptionalCallingConv OptionalAttrs Type Value ParamList
+///       OptionalAttrs OptionalOperandBundles 'to' TypeAndValue
+///       '[' LabelList ']'
+bool LLParser::ParseCallBr(Instruction *&Inst, PerFunctionState &PFS) {
+  LocTy CallLoc = Lex.getLoc();
+  AttrBuilder RetAttrs, FnAttrs;
+  std::vector<unsigned> FwdRefAttrGrps;
+  LocTy NoBuiltinLoc;
+  unsigned CC;
+  Type *RetType = nullptr;
+  LocTy RetTypeLoc;
+  ValID CalleeID;
+  SmallVector<ParamInfo, 16> ArgList;
+  SmallVector<OperandBundleDef, 2> BundleList;
+
+  BasicBlock *DefaultDest;
+  if (ParseOptionalCallingConv(CC) || ParseOptionalReturnAttrs(RetAttrs) ||
+      ParseType(RetType, RetTypeLoc, true /*void allowed*/) ||
+      ParseValID(CalleeID) || ParseParameterList(ArgList, PFS) ||
+      ParseFnAttributeValuePairs(FnAttrs, FwdRefAttrGrps, false,
+                                 NoBuiltinLoc) ||
+      ParseOptionalOperandBundles(BundleList, PFS) ||
+      ParseToken(lltok::kw_to, "expected 'to' in callbr") ||
+      ParseTypeAndBasicBlock(DefaultDest, PFS) ||
+      ParseToken(lltok::lsquare, "expected '[' in callbr"))
+    return true;
+
+  // Parse the destination list.
+  SmallVector<BasicBlock *, 16> IndirectDests;
+
+  if (Lex.getKind() != lltok::rsquare) {
+    BasicBlock *DestBB;
+    if (ParseTypeAndBasicBlock(DestBB, PFS))
+      return true;
+    IndirectDests.push_back(DestBB);
+
+    while (EatIfPresent(lltok::comma)) {
+      if (ParseTypeAndBasicBlock(DestBB, PFS))
+        return true;
+      IndirectDests.push_back(DestBB);
+    }
+  }
+
+  if (ParseToken(lltok::rsquare, "expected ']' at end of block list"))
+    return true;
+
+  // If RetType is a non-function pointer type, then this is the short syntax
+  // for the call, which means that RetType is just the return type.  Infer the
+  // rest of the function argument types from the arguments that are present.
+  FunctionType *Ty = dyn_cast<FunctionType>(RetType);
+  if (!Ty) {
+    // Pull out the types of all of the arguments...
+    std::vector<Type *> ParamTypes;
+    for (unsigned i = 0, e = ArgList.size(); i != e; ++i)
+      ParamTypes.push_back(ArgList[i].V->getType());
+
+    if (!FunctionType::isValidReturnType(RetType))
+      return Error(RetTypeLoc, "Invalid result type for LLVM function");
+
+    Ty = FunctionType::get(RetType, ParamTypes, false);
+  }
+
+  CalleeID.FTy = Ty;
+
+  // Look up the callee.
+  Value *Callee;
+  if (ConvertValIDToValue(PointerType::getUnqual(Ty), CalleeID, Callee, &PFS,
+                          /*IsCall=*/true))
+    return true;
+
+  if (isa<InlineAsm>(Callee) && !Ty->getReturnType()->isVoidTy())
+    return Error(RetTypeLoc, "asm-goto outputs not supported");
+
+  // Set up the Attribute for the function.
+  SmallVector<Value *, 8> Args;
+  SmallVector<AttributeSet, 8> ArgAttrs;
+
+  // Loop through FunctionType's arguments and ensure they are specified
+  // correctly.  Also, gather any parameter attributes.
+  FunctionType::param_iterator I = Ty->param_begin();
+  FunctionType::param_iterator E = Ty->param_end();
+  for (unsigned i = 0, e = ArgList.size(); i != e; ++i) {
+    Type *ExpectedTy = nullptr;
+    if (I != E) {
+      ExpectedTy = *I++;
+    } else if (!Ty->isVarArg()) {
+      return Error(ArgList[i].Loc, "too many arguments specified");
+    }
+
+    if (ExpectedTy && ExpectedTy != ArgList[i].V->getType())
+      return Error(ArgList[i].Loc, "argument is not of expected type '" +
+                                       getTypeString(ExpectedTy) + "'");
+    Args.push_back(ArgList[i].V);
+    ArgAttrs.push_back(ArgList[i].Attrs);
+  }
+
+  if (I != E)
+    return Error(CallLoc, "not enough parameters specified for call");
+
+  if (FnAttrs.hasAlignmentAttr())
+    return Error(CallLoc, "callbr instructions may not have an alignment");
+
+  // Finish off the Attribute and check them
+  AttributeList PAL =
+      AttributeList::get(Context, AttributeSet::get(Context, FnAttrs),
+                         AttributeSet::get(Context, RetAttrs), ArgAttrs);
+
+  CallBrInst *CBI =
+      CallBrInst::Create(Ty, Callee, DefaultDest, IndirectDests, Args,
+                         BundleList);
+  CBI->setCallingConv(CC);
+  CBI->setAttributes(PAL);
+  ForwardRefAttrGroups[CBI] = FwdRefAttrGrps;
+  Inst = CBI;
+  return false;
+}
+
 //===----------------------------------------------------------------------===//
 // Binary Operators.
 //===----------------------------------------------------------------------===//
diff --git a/llvm/lib/AsmParser/LLParser.h b/llvm/lib/AsmParser/LLParser.h
index d8efbb1cf10..95aea0c775a 100644
--- a/llvm/lib/AsmParser/LLParser.h
+++ b/llvm/lib/AsmParser/LLParser.h
@@ -570,6 +570,7 @@ namespace llvm {
     bool ParseCatchSwitch(Instruction *&Inst, PerFunctionState &PFS);
     bool ParseCatchPad(Instruction *&Inst, PerFunctionState &PFS);
     bool ParseCleanupPad(Instruction *&Inst, PerFunctionState &PFS);
+    bool ParseCallBr(Instruction *&Inst, PerFunctionState &PFS);
 
     bool ParseUnaryOp(Instruction *&Inst, PerFunctionState &PFS, unsigned Opc,
                       unsigned OperandType);
diff --git a/llvm/lib/AsmParser/LLToken.h b/llvm/lib/AsmParser/LLToken.h
index 41899b29ce5..88eeae11a4b 100644
--- a/llvm/lib/AsmParser/LLToken.h
+++ b/llvm/lib/AsmParser/LLToken.h
@@ -327,6 +327,7 @@ enum Kind {
   kw_catchret,
   kw_catchpad,
   kw_cleanuppad,
+  kw_callbr,
 
   kw_alloca,
   kw_load,