TableGen asserts on invalid cast

[arsenm]

// RUN: llvm-tblgen -gen-dag-isel -I %p/../../include %s -o - | FileCheck -check-prefix=ISEL %s

include "llvm/Target/Target.td"

class MyReg<string n>
  : Register<n> {
  let Namespace = "MyTarget";
}

def X0 : MyReg<"x0">;
def X1 : MyReg<"x1">;

def XRegs : RegisterClass<"MyTarget", [i64], 64, (add X0, X1)>;

class TestInstruction : Instruction {
  let Size = 2;
  let Namespace = "MyTarget";
  let hasSideEffects = false;
  let hasExtraSrcRegAllocReq = false;
  let hasExtraDefRegAllocReq = false;

  field bits<16> Inst;
  bits<3> dst;
  bits<3> src;
  bits<3> opcode;

  let Inst{2-0} = dst;
  let Inst{5-3} = src;
  let Inst{7-5} = opcode;
}

def MY_LOAD : TestInstruction {
  let OutOperandList = (outs XRegs:$dst);
  let InOperandList = (ins ptr_rc:$ptr);
  let AsmString = "my_load $dst, $ptr";
  let opcode = 0;
}

def : Pat<
  (i64 (load (iPTR:$src))),
  (MY_LOAD $val, $src)
>;

def MyTargetISA : InstrInfo;
def MyTarget : Target { let InstructionSet = MyTargetISA; }

This testcase hits:

error: no check strings found with prefix 'ISEL:'
anonymous_10320: /Users/matt/src/llvm-project/llvm/test/TableGen/cast-error-assert.td:39:1: error: In anonymous_10320: Type cast only takes one operand!
def : Pat<
^
Assertion failed: (Index < Length && "Invalid index!"), function operator[], file ArrayRef.h, line 253.
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace and instructions to reproduce the bug.
Stack dump:
0.	Program arguments: /Users/matt/src/llvm-project/build_debug/bin/llvm-tblgen -gen-dag-isel -I /Users/matt/src/llvm-project/llvm/test/TableGen/../../include /Users/matt/src/llvm-project/llvm/test/TableGen/cast-error-assert.td -o -
 #0 0x0000000101579968 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/Users/matt/src/llvm-project/build_debug/bin/llvm-tblgen+0x100749968)
 #1 0x0000000101579f18 PrintStackTraceSignalHandler(void*) (/Users/matt/src/llvm-project/build_debug/bin/llvm-tblgen+0x100749f18)
 #2 0x0000000101577764 llvm::sys::RunSignalHandlers() (/Users/matt/src/llvm-project/build_debug/bin/llvm-tblgen+0x100747764)
 #3 0x000000010157b940 SignalHandler(int, __siginfo*, void*) (/Users/matt/src/llvm-project/build_debug/bin/llvm-tblgen+0x10074b940)
 #4 0x0000000185500624 (/usr/lib/system/libsystem_platform.dylib+0x1804ac624)
 #5 0x00000001854c688c (/usr/lib/system/libsystem_pthread.dylib+0x18047288c)
 #6 0x00000001853cfc60 (/usr/lib/system/libsystem_c.dylib+0x18037bc60)
 #7 0x00000001853ceeec (/usr/lib/system/libsystem_c.dylib+0x18037aeec)
 #8 0x0000000100f5995c llvm::ArrayRef<llvm::Init const*>::operator[](unsigned long) const (/Users/matt/src/llvm-project/build_debug/bin/llvm-tblgen+0x10012995c)
 #9 0x0000000100f56104 llvm::DagInit::getArg(unsigned int) const (/Users/matt/src/llvm-project/build_debug/bin/llvm-tblgen+0x100126104)
#10 0x0000000100f96f5c llvm::TreePattern::ParseTreePattern(llvm::Init const*, llvm::StringRef)::$_0::operator()(llvm::DagInit const*, llvm::StringRef) const (/Users/matt/src/llvm-project/build_debug/bin/llvm-tblgen+0x100166f5c)
#11 0x0000000100f95b04 llvm::TreePattern::ParseTreePattern(llvm::Init const*, llvm::StringRef) (/Users/matt/src/llvm-project/build_debug/bin/llvm-tblgen+0x100165b04)
#12 0x0000000100f96308 llvm::TreePattern::ParseTreePattern(llvm::Init const*, llvm::StringRef) (/Users/matt/src/llvm-project/build_debug/bin/llvm-tblgen+0x100166308)
#13 0x0000000100f96f94 llvm::TreePattern::ParseTreePattern(llvm::Init const*, llvm::StringRef)::$_0::operator()(llvm::DagInit const*, llvm::StringRef) const (/Users/matt/src/llvm-project/build_debug/bin/llvm-tblgen+0x100166f94)
#14 0x0000000100f95b04 llvm::TreePattern::ParseTreePattern(llvm::Init const*, llvm::StringRef) (/Users/matt/src/llvm-project/build_debug/bin/llvm-tblgen+0x100165b04)
#15 0x0000000100f9687c llvm::TreePattern::TreePattern(llvm::Record const*, llvm::DagInit const*, bool, llvm::CodeGenDAGPatterns&) (/Users/matt/src/llvm-project/build_debug/bin/llvm-tblgen+0x10016687c)
#16 0x0000000100f968e0 llvm::TreePattern::TreePattern(llvm::Record const*, llvm::DagInit const*, bool, llvm::CodeGenDAGPatterns&) (/Users/matt/src/llvm-project/build_debug/bin/llvm-tblgen+0x1001668e0)
#17 0x0000000100f9a554 llvm::CodeGenDAGPatterns::ParsePatterns() (/Users/matt/src/llvm-project/build_debug/bin/llvm-tblgen+0x10016a554)
#18 0x0000000100f98db4 llvm::CodeGenDAGPatterns::CodeGenDAGPatterns(llvm::RecordKeeper const&, std::__1::function<void (llvm::TreePattern*)>) (/Users/matt/src/llvm-project/build_debug/bin/llvm-tblgen+0x100168db4)
#19 0x0000000100f9bc04 llvm::CodeGenDAGPatterns::CodeGenDAGPatterns(llvm::RecordKeeper const&, std::__1::function<void (llvm::TreePattern*)>) (/Users/matt/src/llvm-project/build_debug/bin/llvm-tblgen+0x10016bc04)
#20 0x00000001011b81f8 (anonymous namespace)::DAGISelEmitter::DAGISelEmitter(llvm::RecordKeeper const&) (/Users/matt/src/llvm-project/build_debug/bin/llvm-tblgen+0x1003881f8)

[pchaudhuri-nv]

Haven't used PatFrag, so a basic question... what is the issue with the above pattern ? While debugging I see that the "Dag" to be typecasted has no arguments, so it asserts. Do we expect a complex pattern operand after load that processes "src" and also generates "val" ?

Also, as a part of this "issue" we should be change it to PrintFatalError for cleaner error reporting and not crash, right ? I do see multiple instances in the file where we prefer to crash and not use the error reporting mechanism. Not sure about the reason...

[arsenm]

The extra parentheses around (iPTR:$src) should be removed. Not sure exactly why it's thinking this is a cast.

Also, as a part of this "issue" we should be change it to PrintFatalError for cleaner error reporting and not crash, right ?

Yes

I do see multiple instances in the file where we prefer to crash and not use the error reporting mechanism. Not sure about the reason...

Crappy ancient code, tablegen used to be a lot worse about using assert-based "error handling'. Crashing is never good

[pchaudhuri-nv]

I see thank you for explaining.
I had replaced the assert with PrintFatalError and it worked as expected.

I can probably create a PR for this one if no-one is working on this. (I want to frankly admit, I have never created PR for LLVM project, so might take some time even for the simple thing).

Also, I think in general, it would be good to clean up such asserts. I was trying to collect similar kind of issues under the initiative "FriendlyTableGen" - https://discourse.llvm.org/t/llvm-tablegen-friendlytablegen-an-initiative-to-make-llvm-tablegen-more-user-friendly/87613/1 and I have documented this issue in the Google sheet attached. (Anyone who has bandwidth can take up the issue of their choice, like I am working on introducing SMLoc for Init classes.)

[arsenm]

If you're interested in improving diagnostics, the diagnostics for !cond are quite bad. That was more of an obstacle to my recent work than this assert

[pchaudhuri-nv]

Hello @arsenm ,

Apologies for delayed response. This is the small MR that I created which addresses only a few errors. #161417 . Can you kindly help review ?