Are multi-output patterns in TableGen supposed to work, or is that a known limitation in the current implementation?
If I have TableGen code like the following…
1242 def SDTTestNode : SDTypeProfile<2, 1, [SDTCisSameAs<0, 1>]>;
1243 def TestNode : SDNode<“NVPTXISD::TestNode”, SDTTestNode>;
1244
1245 def MyTestNode : NVPTXInst<(outs Int32Regs:$dst0, Int32Regs:$dst1),
1246 (ins Int32Regs:$a),
1247 “test $dst0, $dst1, $a;”,
1248 [(set Int32Regs:$dst0, Int32Regs:$dst1, (TestNode Int32Regs:$a))]>;
… TableGen crashes with the following stack trace:
#0 0x00007fff8f372212 in __pthread_kill ()
#1 0x00007fff8dc0eaf4 in pthread_kill ()
#2 0x00000001003a978b in raise (sig=6) at Signals.inc:345
#3 0x00000001003a9842 in abort () at Signals.inc:362
#4 0x00000001003a9821 in __assert_rtn (func=0x1003d0d14 “operator”, file=0x1003b169e “/Users/jholewinski/projects/llvm/src/llvm/include/llvm/ADT/SmallVector.h”, line=139, expr=0x1003b16e7 “begin() + idx < end()”) at Signals.inc:358
#5 0x00000001000ca394 in llvm::SmallVectorTemplateCommon<llvm::EEVT::TypeSet, void>::operator (this=0x10384fed0, idx=1) at SmallVector.h:139
#6 0x00000001000c965b in llvm::TreePatternNode::getExtType (this=0x10384fed0, ResNo=1) at CodeGenDAGPatterns.h:349
#7 0x00000001000bd615 in llvm::CodeGenDAGPatterns::ParseInstructions (this=0x7fff5fbff0b0) at /Users/jholewinski/projects/llvm/src/llvm/utils/TableGen/CodeGenDAGPatterns.cpp:2782
#8 0x00000001000b7143 in llvm::CodeGenDAGPatterns::CodeGenDAGPatterns (this=0x7fff5fbff0b0, R=@0x7fff5fbff670) at /Users/jholewinski/projects/llvm/src/llvm/utils/TableGen/CodeGenDAGPatterns.cpp:2077
#9 0x00000001000b6a3d in llvm::CodeGenDAGPatterns::CodeGenDAGPatterns (this=0x7fff5fbff0b0, R=@0x7fff5fbff670) at /Users/jholewinski/projects/llvm/src/llvm/utils/TableGen/CodeGenDAGPatterns.cpp:2091
#10 0x000000010024cd15 in InstrInfoEmitter (this=0x7fff5fbff0a8, R=@0x7fff5fbff670) at /Users/jholewinski/projects/llvm/src/llvm/utils/TableGen/InstrInfoEmitter.cpp:39
#11 0x0000000100248e8d in InstrInfoEmitter (this=0x7fff5fbff0a8, R=@0x7fff5fbff670) at /Users/jholewinski/projects/llvm/src/llvm/utils/TableGen/InstrInfoEmitter.cpp:39
#12 0x0000000100248e36 in llvm::EmitInstrInfo (RK=@0x7fff5fbff670, OS=@0x7fff5fbff518) at /Users/jholewinski/projects/llvm/src/llvm/utils/TableGen/InstrInfoEmitter.cpp:420
#13 0x00000001002d0930 in LLVMTableGenMain (OS=@0x7fff5fbff518, Records=@0x7fff5fbff670) at /Users/jholewinski/projects/llvm/src/llvm/utils/TableGen/TableGen.cpp:106
#14 0x00000001002e8385 in llvm::TableGenMain (argv0=0x7fff5fbffa88 “/Users/jholewinski/projects/llvm/build/bin/llvm-tblgen”, MainFn=0x1002d0880 ) at /Users/jholewinski/projects/llvm/src/llvm/lib/TableGen/Main.cpp:117
#15 0x00000001002d0864 in main (argc=11, argv=0x7fff5fbff8f8) at /Users/jholewinski/projects/llvm/src/llvm/utils/TableGen/TableGen.cpp:181
The fault occurs in CodeGenDAGPatterns.cpp:
2781 for (unsigned i = 0; i != NumResults; ++i)
2782 ResultPattern->setType(i, Res0Node->getExtType(i));
Res0Node has only 1 type, but it is expected to have 2.
Looking at the X86 back-end code, it looks like there do exist multi-output instructions, but they all use physical (implicit) registers for the second destination, not arbitrary register types. And if I change the second destination to be a certain physical register, this problem goes away in my code. Is this just not a supported case currently? Or am I doing something wrong?
This is my first time looking into the TableGen internals, so I can’t spot anything obviously wrong with the TableGen tool code.