Allow "callbr" to return non-void values

[void]

Summary

THIS IS A WIP!

Remove the restrictions that preventing "callbr" from returning non-void
values. The value returned by "callbr" is only valid on the "normal" path.
Values used on "abnormal" paths are poisoned.

Allow output constraints on "asm goto"

clang/include/clang/AST/Stmt.h

bool isAsmGoto() const {
     return NumLabels > 0;
   }
 
   unsigned getNumLabels() const {
     return NumLabels;
   }
 
   IdentifierInfo *getLabelIdentifier(unsigned i) const {
-    return Names[i + NumInputs];
+    return Names[i + NumOutputs + NumInputs];
   }
 
   AddrLabelExpr *getLabelExpr(unsigned i) const;
   StringRef getLabelName(unsigned i) const;
   using labels_iterator = CastIterator<AddrLabelExpr>;
   using const_labels_iterator = ConstCastIterator<AddrLabelExpr>;
   using labels_range = llvm::iterator_range<labels_iterator>;
   using labels_const_range = llvm::iterator_range<const_labels_iterator>;
 
   labels_iterator begin_labels() {
-    return &Exprs[0] + NumInputs;
+    return &Exprs[0] + NumOutputs + NumInputs;
   }
 
   labels_iterator end_labels() {
-    return &Exprs[0] + NumInputs + NumLabels;
+    return &Exprs[0] + NumOutputs + NumInputs + NumLabels;
   }
 
   labels_range labels() {
     return labels_range(begin_labels(), end_labels());
   }
 
   const_labels_iterator begin_labels() const {
-    return &Exprs[0] + NumInputs;
+    return &Exprs[0] + NumOutputs + NumInputs;
   }
 
   const_labels_iterator end_labels() const {
-    return &Exprs[0] + NumInputs + NumLabels;
+    return &Exprs[0] + NumOutputs + NumInputs + NumLabels;
   }
 
   labels_const_range labels() const {
     return labels_const_range(begin_labels(), end_labels());
   }
 
 private:
   void setOutputsAndInputsAndClobbers(const ASTContext &C,

clang/lib/AST/Stmt.cpp

Expr *GCCAsmStmt::getInputExpr(unsigned i) {
   return cast<Expr>(Exprs[i + NumOutputs]);
 }
 
 void GCCAsmStmt::setInputExpr(unsigned i, Expr *E) {
   Exprs[i + NumOutputs] = E;
 }
 
 AddrLabelExpr *GCCAsmStmt::getLabelExpr(unsigned i) const {
-  return cast<AddrLabelExpr>(Exprs[i + NumInputs]);
+  return cast<AddrLabelExpr>(Exprs[i + NumOutputs + NumInputs]);
 }
 
 StringRef GCCAsmStmt::getLabelName(unsigned i) const {
   return getLabelExpr(i)->getLabel()->getName();
 }
 
 /// getInputConstraint - Return the specified input constraint.  Unlike output
 /// constraints, these can be empty.
int GCCAsmStmt::getNamedOperand(StringRef SymbolicName) const {
   }
 
   for (unsigned i = 0, e = getNumInputs(); i != e; ++i)
     if (getInputName(i) == SymbolicName)
       return getNumOutputs() + NumPlusOperands + i;
 
   for (unsigned i = 0, e = getNumLabels(); i != e; ++i)
     if (getLabelName(i) == SymbolicName)
-      return i + getNumInputs();
+      return i + getNumOutputs() + getNumInputs();
 
   // Not found.
   return -1;
 }
 
 /// AnalyzeAsmString - Analyze the asm string of the current asm, decomposing
 /// it into pieces.  If the asm string is erroneous, emit errors and return
 /// true, otherwise return false.

clang/lib/Parse/ParseStmtAsm.cpp

StmtResult Parser::ParseAsmStatement(bool &msAsm) {
 
   // Parse Outputs, if present.
   bool AteExtraColon = false;
   if (Tok.is(tok::colon) || Tok.is(tok::coloncolon)) {
     // In C++ mode, parse "::" like ": :".
     AteExtraColon = Tok.is(tok::coloncolon);
     ConsumeToken();
 
-    if (!AteExtraColon && isGotoAsm && Tok.isNot(tok::colon)) {
-      Diag(Tok, diag::err_asm_goto_cannot_have_output);
-      SkipUntil(tok::r_paren, StopAtSemi);
-      return StmtError();
-    }
-
     if (!AteExtraColon && ParseAsmOperandsOpt(Names, Constraints, Exprs))
       return StmtError();
   }
 
   unsigned NumOutputs = Names.size();
 
   // Parse Inputs, if present.
   if (AteExtraColon || Tok.is(tok::colon) || Tok.is(tok::coloncolon)) {

clang/lib/Sema/SemaStmtAsm.cpp

StmtResult Sema::ActOnGCCAsmStmt(SourceLocation AsmLoc, bool IsSimple,
 
   // Validate constraints and modifiers.
   for (unsigned i = 0, e = Pieces.size(); i != e; ++i) {
     GCCAsmStmt::AsmStringPiece &Piece = Pieces[i];
     if (!Piece.isOperand()) continue;
 
     // Look for the correct constraint index.
     unsigned ConstraintIdx = Piece.getOperandNo();
+    unsigned NumOperands = NS->getNumOutputs() + NS->getNumInputs();
     // Labels are the last in the Exprs list.
-    if (NS->isAsmGoto() && ConstraintIdx >= NS->getNumInputs())
+    if (NS->isAsmGoto() && ConstraintIdx >= NumOperands)
       continue;
-    unsigned NumOperands = NS->getNumOutputs() + NS->getNumInputs();
     // Look for the (ConstraintIdx - NumOperands + 1)th constraint with
     // modifier '+'.
     if (ConstraintIdx >= NumOperands) {
       unsigned I = 0, E = NS->getNumOutputs();
 
       for (unsigned Cnt = ConstraintIdx - NumOperands; I != E; ++I)
         if (OutputConstraintInfos[I].isReadWrite() && Cnt-- == 0) {
           ConstraintIdx = I;

clang/test/Parser/asm-goto.c

fgoto2 (void)
   __asm__ volatile goto (""
             :: [a] "r,m" (a), [b] "r,m" (b), [c] "r,m" (c), [d] "r,m" (d),
                [e] "r,m" (e), [f] "r,m" (f), [g] "r,m" (g), [h] "r,m" (h),
                [i] "r,m" (i), [j] "r,m" (j), [k] "r,m" (k), [l] "r,m" (l)
             :: lab);
   lab: return;
 }
 
-int zoo ()
+int
+fgoto3 (int x)
+{
+  __asm__ volatile goto ("decl %0; jnz %l[a]"
+                         : "=r" (x) : "m" (x) : "memory" : a);
+a:
+  return -x;
+}
+
+int
+zoo (void)
 {
   int x,cond,*e;
   // expected-error@+1 {{expected ')'}}
   asm ("mov %[e], %[e]" : : [e] "rm" (*e)::a)
-  // expected-error@+1 {{'asm goto' cannot have output constraints}}
-  asm goto ("decl %0; jnz %l[a]" :"=r"(x): "m"(x) : "memory" : a);
-  // expected-error@+1 {{expected identifie}}
+  // expected-error@+1 {{expected identifier}}
   asm goto ("decl %0;" :: "m"(x) : "memory" : );
   // expected-error@+1 {{expected ':'}}
   asm goto ("decl %0;" :: "m"(x) : "memory" );
   // expected-error@+1 {{use of undeclared label 'x'}}
   asm goto ("decl %0;" :: "m"(x) : "memory" :x);
   // expected-error@+1 {{use of undeclared label 'b'}}
   asm goto ("decl %0;" :: "m"(x) : "memory" :b);
   // expected-error@+1 {{invalid operand number in inline asm string}}
   asm goto ("testl %0, %0; jne %l3;" :: "r"(cond)::label_true, loop);
   // expected-error@+1 {{unknown symbolic operand name in inline assembly string}}
   asm goto ("decl %0; jnz %l[b]" :: "m"(x) : "memory" : a);
 a:
 label_true:
 loop:
   return 0;
 }

clang/test/Parser/asm-goto.cpp

 // RUN: %clang_cc1 -triple i386-pc-linux-gnu -fsyntax-only -verify -std=c++11 %s
 // RUN: %clang_cc1 -triple x86_64-pc-linux-gnu -fsyntax-only -verify -std=c++11 %s
 
 int zoo ()
 {
   int x,cond,*e;
   // expected-error@+1 {{expected ')'}}
   asm ("mov %[e], %[e]" : : [e] "rm" (*e)::a)
-  // expected-error@+1  {{'asm goto' cannot have output constraints}}
-  asm goto ("decl %0; jnz %l[a]" :"=r"(x): "m"(x) : "memory" : a);
-  // expected-error@+1 {{expected identifie}}
+  // expected-error@+1 {{expected identifier}}
   asm goto ("decl %0;" :: "m"(x) : "memory" : );
   // expected-error@+1  {{expected ':'}}
   asm goto ("decl %0;" :: "m"(x) : "memory" );
   // expected-error@+1 {{use of undeclared label 'x'}}
   asm goto ("decl %0;" :: "m"(x) : "memory" :x);
   // expected-error@+1 {{use of undeclared label 'b'}}
   asm goto ("decl %0;" :: "m"(x) : "memory" :b);
   // expected-error@+1 {{invalid operand number in inline asm string}}

 {
   __asm__ volatile goto (""
             :: [a] "r,m" (a), [b] "r,m" (b), [c] "r,m" (c), [d] "r,m" (d),
                [e] "r,m" (e), [f] "r,m" (f), [g] "r,m" (g), [h] "r,m" (h),
                [i] "r,m" (i), [j] "r,m" (j), [k] "r,m" (k), [l] "r,m" (l)
             :: lab);
   lab: return;
 }
+
+int
+fgoto3 (int x)
+{
+  __asm__ volatile goto ("decl %0; jnz %l[a]"
+                         : "=r" (x) : "m" (x) : "memory" : a);
+a:
+  return -x;
+}

llvm/lib/AsmParser/LLParser.cpp

bool LLParser::ParseCallBr(Instruction *&Inst, PerFunctionState &PFS) {
   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();

llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp

void SelectionDAGBuilder::visitCallBr(const CallBrInst &I) {
   // have to do anything here to lower funclet bundles.
   assert(!I.hasOperandBundlesOtherThan(
              {LLVMContext::OB_deopt, LLVMContext::OB_funclet}) &&
          "Cannot lower callbrs with arbitrary operand bundles yet!");
 
   assert(isa<InlineAsm>(I.getCalledValue()) &&
          "Only know how to handle inlineasm callbr");
   visitInlineAsm(&I);
+  CopyToExportRegsIfNeeded(&I);
 
   // Retrieve successors.
   MachineBasicBlock *Return = FuncInfo.MBBMap[I.getDefaultDest()];
 
   // Update successor info.
   addSuccessorWithProb(CallBrMBB, Return);
   for (unsigned i = 0, e = I.getNumIndirectDests(); i < e; ++i) {
     MachineBasicBlock *Target = FuncInfo.MBBMap[I.getIndirectDest(i)];

llvm/lib/IR/Verifier.cpp

Assert(BI.getDestination(i)->getType()->isLabelTy(),
            "Indirectbr destinations must all have pointer type!", &BI);
 
   visitTerminator(BI);
 }
 
 void Verifier::visitCallBrInst(CallBrInst &CBI) {
   Assert(CBI.isInlineAsm(), "Callbr is currently only used for asm-goto!",
          &CBI);
-  Assert(CBI.getType()->isVoidTy(), "Callbr return value is not supported!",
-         &CBI);
   for (unsigned i = 0, e = CBI.getNumSuccessors(); i != e; ++i)
     Assert(CBI.getSuccessor(i)->getType()->isLabelTy(),
            "Callbr successors must all have pointer type!", &CBI);
   for (unsigned i = 0, e = CBI.getNumOperands(); i != e; ++i) {
     Assert(i >= CBI.getNumArgOperands() || !isa<BasicBlock>(CBI.getOperand(i)),
            "Using an unescaped label as a callbr argument!", &CBI);
     if (isa<BasicBlock>(CBI.getOperand(i)))
       for (unsigned j = i + 1; j != e; ++j)

llvm/test/CodeGen/X86/callbr-asm-outputs.ll

-; RUN: not llc -mtriple=i686-- < %s 2> %t
-; RUN: FileCheck %s < %t
+; RUN: llc -mtriple=i686-- < %s | FileCheck %s
 
-; CHECK: error: asm-goto outputs not supported
+; A test for asm-goto output
 
-; A test for asm-goto output prohibition
-
-define i32 @test(i32 %a) {
+; CHECK-LABEL: test1:
+; CHECK:       movl 4(%esp), %eax
+; CHECK-NEXT:  addl $4, %eax
+; CHECK-NEXT:  #APP
+; CHECK-NEXT:  xorl %eax, %eax
+; CHECK-NEXT:  jmp .Ltmp0
+; CHECK-NEXT:  #NO_APP
+; CHECK-NEXT:  .LBB0_1:
+; CHECK-NEXT:  retl
+; CHECK-NEXT:  .Ltmp0:
+define i32 @test1(i32 %x) {
 entry:
-  %0 = add i32 %a, 4
-  %1 = callbr i32 asm "xorl $1, $1; jmp ${1:l}", "=&r,r,X,~{dirflag},~{fpsr},~{flags}"(i32 %0, i8* blockaddress(@test, %fail)) to label %normal [label %fail]
+  %add = add nsw i32 %x, 4
+  %ret = callbr i32 asm "xorl $1, $0; jmp ${2:l}", "=r,r,X,~{dirflag},~{fpsr},~{flags}"(i32 %add, i8* blockaddress(@test1, %abnormal))
+          to label %normal [label %abnormal]
 
 normal:
-  ret i32 %1
+  ret i32 %ret
 
-fail:
+abnormal:
   ret i32 1
 }