DAGISelEmitter not looking up instruction namespace accurately.

[npatil2]

Bugzilla Link	1001
Resolution	FIXED
Resolved on	Feb 22, 2010 12:53
Version	trunk
OS	Linux

Extended Description

I was trying to write my own simple LLVM backend for my own simple ISA when I
ran into the following error message:

MCGenDAGISel.inc: In member function
'llvm::SDNode*::MCDAGToDAGISel::SelectCode(llvm::SDOperand)':
MCGenDAGISel.inc:463: error: 'INSTRUCTION_LIST_END' is not a member of
'llvm::TargetInstrInfo'

My target description had only one instruction NOP. The problem disappears when
I change NOP to ADD. In fact anything alphabetically before INLINEASM is
okay. (INLINEASM & PHINODE are in namespace TargetInstrInfo.) I have traced
down the problem to utils/TableGen/DAGISelEmitter.cpp:3390, where we only look
at the first instruction in the list of all instructions. So if there happen to
be no instructions alphabetically before INLINEASM, we get screwed.

Please let me know if you need any more information :)

[lattner]

This looks like a relatively easy bug to fix, but a hard one for me to test without an example. Can you
propose a patch please?

Thanks,

-Chris

[npatil2]

There's two ways. (I think I'd prefer (a).)

(a) Check for TargetInstrInfo explicitly

--- DAGISelEmitter.cpp 8 Nov 2006 23:01:03 -0000 1.281
+++ DAGISelEmitter.cpp 14 Nov 2006 03:11:13 -0000
@@ -3387,7 +3387,13 @@
}

void DAGISelEmitter::EmitInstructionSelector(std::ostream &OS) {

• std::string InstNS = Target.inst_begin()->second.Namespace;

• std::string InstNS;

• CodeGenTarget::inst_iterator i;

• for (i = Target.inst_begin(); i != Target.inst_end(); ++i) {

• InstNS = i->second.Namespace;

• if (InstNS != "TargetInstrInfo")

•   break;
  

• }
  if (!InstNS.empty()) InstNS += "::";

  // Group the patterns by their top-level opcodes.

---

(b) Check for INLINEASM & PHI explicitly:

diff -u -r1.281 DAGISelEmitter.cpp
--- DAGISelEmitter.cpp 8 Nov 2006 23:01:03 -0000 1.281
+++ DAGISelEmitter.cpp 14 Nov 2006 03:16:36 -0000
@@ -3387,7 +3387,15 @@
}

void DAGISelEmitter::EmitInstructionSelector(std::ostream &OS) {

• std::string InstNS = Target.inst_begin()->second.Namespace;

• std::string InstNS;

• CodeGenTarget::inst_iterator i;

• for (i = Target.inst_begin(); i != Target.inst_end(); ++i) {

• std::string name = i->second.TheDef->getName();

• if (name != "INLINEASM" && name != "PHI") {

•   InstNS = i->second.Namespace;
  

•   break;
  

• }

• }
  if (!InstNS.empty()) InstNS += "::";

  // Group the patterns by their top-level opcodes.

---

Thanks,

[lattner]

Option #​1 sounds good to me! Thanks, I applied your patch:
http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20061120/040138.html

Thanks,

-Chris