[llvm] r255344 - [TableGen] Correct Namespace lookup with AltNames in AsmWriterEmitter

[Hal Finkel via llvm-commits]

Author: hfinkel
Date: Fri Dec 11 11:31:27 2015
New Revision: 255344

URL: http://llvm.org/viewvc/llvm-project?rev=255344&view=rev
Log:
[TableGen] Correct Namespace lookup with AltNames in AsmWriterEmitter

AsmWriterEmitter will generate a getRegisterName function with an alternate
register name index as its second argument if the target makes use of them. The
enum of these values is generated in RegisterInfoEmitter. The getRegisterName
generator would assume the namespace could always be found by reading index 1
of the list of AltNameIndices, but this will fail if this list is sorted such
that the NoRegAltName is at index 1. Because this list is sorted by record name
(in CodeGenTarget::ReadRegAltNameIndices), you only run in to problems if your
MyTargetRegisterInfo.td defines a single RegAltNameIndex that sorts lexically
before NoRegAltName.

For example, if a target has something like

  def AnAltNameIndex : RegAltNameIndex

and defines RegAltNameIndices for some registers then, prior to this change,
AsmWriterEmitter would generate references to

  ::AnAltNameIndex and ::NoRegAltName

Patch by Alex Bradbury!

Modified:
    llvm/trunk/utils/TableGen/AsmWriterEmitter.cpp

Modified: llvm/trunk/utils/TableGen/AsmWriterEmitter.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/utils/TableGen/AsmWriterEmitter.cpp?rev=255344&r1=255343&r2=255344&view=diff
==============================================================================
--- llvm/trunk/utils/TableGen/AsmWriterEmitter.cpp (original)
+++ llvm/trunk/utils/TableGen/AsmWriterEmitter.cpp Fri Dec 11 11:31:27 2015
@@ -586,6 +586,8 @@ void AsmWriterEmitter::EmitGetRegisterNa
   const auto &Registers = Target.getRegBank().getRegisters();
   std::vector<Record*> AltNameIndices = Target.getRegAltNameIndices();
   bool hasAltNames = AltNameIndices.size() > 1;
+  std::string Namespace =
+      Registers.front().TheDef->getValueAsString("Namespace");
 
   O <<
   "\n\n/// getRegisterName - This method is automatically generated by tblgen\n"
@@ -610,9 +612,9 @@ void AsmWriterEmitter::EmitGetRegisterNa
     O << "  switch(AltIdx) {\n"
       << "  default: llvm_unreachable(\"Invalid register alt name index!\");\n";
     for (unsigned i = 0, e = AltNameIndices.size(); i < e; ++i) {
-      std::string Namespace = AltNameIndices[1]->getValueAsString("Namespace");
       std::string AltName(AltNameIndices[i]->getName());
-      O << "  case " << Namespace << "::" << AltName << ":\n"
+      std::string Prefix = !Namespace.empty() ? Namespace + "::" : "";
+      O << "  case " << Prefix << AltName << ":\n"
         << "    assert(*(AsmStrs" << AltName << "+RegAsmOffset"
         << AltName << "[RegNo-1]) &&\n"
         << "           \"Invalid alt name index for register!\");\n"