[AVR] AsmParser doesn't reject bad asm, again

[workingjubilee]

This code falls through to binary code emission, at which point it hits an llvm_unreachable. This may save you from getting any further if you've enabled the right CMake variable.

It is probably bad code that should get rejected way earlier.

target datalayout = "e-P1-p:16:8-i8:8-i16:8-i32:8-i64:8-f32:8-f64:8-n8-a:8"
target triple = "avr-unknown-unknown"

define void @main() addrspace(1) #0 {
  call addrspace(0) void asm sideeffect alignstack "st ${0}, ${1}", "e,r,~{sreg},~{memory}"(ptr nonnull inttoptr (i16 37 to ptr), i8 0)
  unreachable
}

attributes #0 = { "target-cpu"="atmega328p" }

And speaking of "should get rejected way earlier": It does IF you have debug assertions enabled!

Backtrace

llc: /root/build/lib/Target/AVR/AVRGenAsmWriter.inc:1424: static const char* llvm::AVRInstPrinter::getRegisterName(llvm::MCRegister, unsigned int): Assertion `*(AsmStrsptr+RegAsmOffsetptr[RegNo-1]) && "Invalid alt name index for register!"' failed.
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace.
Stack dump:
0.	Program arguments: /opt/compiler-explorer/clang-assertions-trunk/bin/llc -o /app/output.s -x86-asm-syntax=intel <source>
1.	Running pass 'Function Pass Manager' on module '<source>'.
2.	Running pass 'AVR Assembly Printer' on function '@main'
 #0 0x0000000003ba9ae8 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/opt/compiler-explorer/clang-assertions-trunk/bin/llc+0x3ba9ae8)
 #1 0x0000000003ba749c SignalHandler(int) Signals.cpp:0:0
 #2 0x0000780202242520 (/lib/x86_64-linux-gnu/libc.so.6+0x42520)
 #3 0x00007802022969fc pthread_kill (/lib/x86_64-linux-gnu/libc.so.6+0x969fc)
 #4 0x0000780202242476 gsignal (/lib/x86_64-linux-gnu/libc.so.6+0x42476)
 #5 0x00007802022287f3 abort (/lib/x86_64-linux-gnu/libc.so.6+0x287f3)
 #6 0x000078020222871b (/lib/x86_64-linux-gnu/libc.so.6+0x2871b)
 #7 0x0000780202239e96 (/lib/x86_64-linux-gnu/libc.so.6+0x39e96)
 #8 0x00000000023ddeda llvm::AVRInstPrinter::printOperand(llvm::MCInst const*, unsigned int, llvm::raw_ostream&) (/opt/compiler-explorer/clang-assertions-trunk/bin/llc+0x23ddeda)
 #9 0x00000000023debb3 llvm::AVRInstPrinter::printInst(llvm::MCInst const*, unsigned long, llvm::StringRef, llvm::MCSubtargetInfo const&, llvm::raw_ostream&) (/opt/compiler-explorer/clang-assertions-trunk/bin/llc+0x23debb3)
#10 0x000000000323fd02 llvm::MCTargetStreamer::prettyPrintAsm(llvm::MCInstPrinter&, unsigned long, llvm::MCInst const&, llvm::MCSubtargetInfo const&, llvm::raw_ostream&) (/opt/compiler-explorer/clang-assertions-trunk/bin/llc+0x323fd02)
#11 0x00000000032a8faa (anonymous namespace)::MCAsmStreamer::emitInstruction(llvm::MCInst const&, llvm::MCSubtargetInfo const&) MCAsmStreamer.cpp:0:0
#12 0x00000000009691c5 (anonymous namespace)::AVRAsmParser::matchAndEmitInstruction(llvm::SMLoc, unsigned int&, llvm::SmallVectorImpl<std::unique_ptr<llvm::MCParsedAsmOperand, std::default_delete<llvm::MCParsedAsmOperand>>>&, llvm::MCStreamer&, unsigned long&, bool) AVRAsmParser.cpp:0:0
#13 0x0000000004bd205a (anonymous namespace)::AsmParser::parseAndMatchAndEmitTargetInstruction((anonymous namespace)::ParseStatementInfo&, llvm::StringRef, llvm::AsmToken, llvm::SMLoc) AsmParser.cpp:0:0
#14 0x0000000004bea616 (anonymous namespace)::AsmParser::parseStatement((anonymous namespace)::ParseStatementInfo&, llvm::MCAsmParserSemaCallback*) (.part.0) AsmParser.cpp:0:0
#15 0x0000000004bdf553 (anonymous namespace)::AsmParser::Run(bool, bool) AsmParser.cpp:0:0
#16 0x0000000002872b2f llvm::AsmPrinter::emitInlineAsm(llvm::StringRef, llvm::MCSubtargetInfo const&, llvm::MCTargetOptions const&, llvm::MDNode const*, llvm::InlineAsm::AsmDialect) const (/opt/compiler-explorer/clang-assertions-trunk/bin/llc+0x2872b2f)
#17 0x00000000028739d7 llvm::AsmPrinter::emitInlineAsm(llvm::MachineInstr const*) const (/opt/compiler-explorer/clang-assertions-trunk/bin/llc+0x28739d7)
#18 0x000000000286cbe6 llvm::AsmPrinter::emitFunctionBody() (/opt/compiler-explorer/clang-assertions-trunk/bin/llc+0x286cbe6)
#19 0x00000000014923c5 llvm::AsmPrinter::runOnMachineFunction(llvm::MachineFunction&) (/opt/compiler-explorer/clang-assertions-trunk/bin/llc+0x14923c5)
#20 0x0000000002b263d9 llvm::MachineFunctionPass::runOnFunction(llvm::Function&) (.part.0) MachineFunctionPass.cpp:0:0
#21 0x00000000031213c0 llvm::FPPassManager::runOnFunction(llvm::Function&) (/opt/compiler-explorer/clang-assertions-trunk/bin/llc+0x31213c0)
#22 0x0000000003121771 llvm::FPPassManager::runOnModule(llvm::Module&) (/opt/compiler-explorer/clang-assertions-trunk/bin/llc+0x3121771)
#23 0x0000000003122027 llvm::legacy::PassManagerImpl::run(llvm::Module&) (/opt/compiler-explorer/clang-assertions-trunk/bin/llc+0x3122027)
#24 0x000000000086aefc compileModule(char**, llvm::LLVMContext&) llc.cpp:0:0
#25 0x0000000000756ae6 main (/opt/compiler-explorer/clang-assertions-trunk/bin/llc+0x756ae6)
#26 0x0000780202229d90 (/lib/x86_64-linux-gnu/libc.so.6+0x29d90)
#27 0x0000780202229e40 __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x29e40)
#28 0x0000000000861c0e _start (/opt/compiler-explorer/clang-assertions-trunk/bin/llc+0x861c0e)
Program terminated with signal: SIGSEGV
Compiler returned: 139

h/t @dianqk

[benshi001]

core dump info

llc: /data/home/bennshi/work/llvm-project/debug/lib/Target/AVR/AVRGenAsmWriter.inc:1430: static const char* llvm::AVRInstPrinter::getRegisterName(llvm::MCRegister, unsigned int): Assertion `*(AsmStrsptr+RegAsmOffsetptr[RegNo-1]) && "Invalid alt name index for register!"' failed.
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace.
Stack dump:
0.      Program arguments: ./bin/llc a.ll
1.      Running pass 'Function Pass Manager' on module 'a.ll'.
2.      Running pass 'AVR Assembly Printer' on function '@main'
 #0 0x0000000004324828 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) /data/home/bennshi/work/llvm-project/llvm/lib/Support/Unix/Signals.inc:723:22
 #1 0x0000000004324c62 PrintStackTraceSignalHandler(void*) /data/home/bennshi/work/llvm-project/llvm/lib/Support/Unix/Signals.inc:798:1
 #2 0x0000000004322558 llvm::sys::RunSignalHandlers() /data/home/bennshi/work/llvm-project/llvm/lib/Support/Signals.cpp:105:20
 #3 0x0000000004324213 SignalHandler(int) /data/home/bennshi/work/llvm-project/llvm/lib/Support/Unix/Signals.inc:413:1
 #4 0x00007fededaaecf0 __restore_rt (/lib64/libpthread.so.0+0x12cf0)
 #5 0x00007fedec7ccacf raise ../sysdeps/unix/sysv/linux/raise.c:51:1
 #6 0x00007fedec79fea5 abort abort.c:81:7
 #7 0x00007fedec79fd79 _nl_load_domain.cold.0 loadmsgcat.c:1177:9
 #8 0x00007fedec7c5426 (/lib64/libc.so.6+0x47426)
 #9 0x00000000026414e2 llvm::AVRInstPrinter::getRegisterName(llvm::MCRegister, unsigned int) /data/home/bennshi/work/llvm-project/debug/lib/Target/AVR/AVRGenAsmWriter.inc:1431:44
#10 0x0000000002641ce3 llvm::AVRInstPrinter::printOperand(llvm::MCInst const*, unsigned int, llvm::raw_ostream&) /data/home/bennshi/work/llvm-project/llvm/lib/Target/AVR/MCTargetDesc/AVRInstPrinter.cpp:129:49
#11 0x0000000002641a39 llvm::AVRInstPrinter::printInst(llvm::MCInst const*, unsigned long, llvm::StringRef, llvm::MCSubtargetInfo const&, llvm::raw_ostream&) /data/home/bennshi/work/llvm-project/llvm/lib/Target/AVR/MCTargetDesc/AVRInstPrinter.cpp:62:10
#12 0x00000000037ed5a4 llvm::MCTargetStreamer::prettyPrintAsm(llvm::MCInstPrinter&, unsigned long, llvm::MCInst const&, llvm::MCSubtargetInfo const&, llvm::raw_ostream&) /data/home/bennshi/work/llvm-project/llvm/lib/MC/MCStreamer.cpp:1109:24
#13 0x00000000038752fa (anonymous namespace)::MCAsmStreamer::emitInstruction(llvm::MCInst const&, llvm::MCSubtargetInfo const&) /data/home/bennshi/work/llvm-project/llvm/lib/MC/MCAsmStreamer.cpp:2449:40
#14 0x00000000020158c7 (anonymous namespace)::AVRAsmParser::emit(llvm::MCInst&, llvm::SMLoc const&, llvm::MCStreamer&) const /data/home/bennshi/work/llvm-project/llvm/lib/Target/AVR/AsmParser/AVRAsmParser.cpp:320:10
#15 0x00000000020159a4 (anonymous namespace)::AVRAsmParser::matchAndEmitInstruction(llvm::SMLoc, unsigned int&, llvm::SmallVectorImpl<std::unique_ptr<llvm::MCParsedAsmOperand, std::default_delete<llvm::MCParsedAsmOperand>>>&, llvm::MCStreamer&, unsigned long&, bool) /data/home/bennshi/work/llvm-project/llvm/lib/Target/AVR/AsmParser/AVRAsmParser.cpp:333:16
#16 0x000000000597a971 (anonymous namespace)::AsmParser::parseAndMatchAndEmitTargetInstruction((anonymous namespace)::ParseStatementInfo&, llvm::StringRef, llvm::AsmToken, llvm::SMLoc) /data/home/bennshi/work/llvm-project/llvm/lib/MC/MCParser/AsmParser.cpp:2390:50
#17 0x000000000597a2b0 (anonymous namespace)::AsmParser::parseStatement((anonymous namespace)::ParseStatementInfo&, llvm::MCAsmParserSemaCallback*) /data/home/bennshi/work/llvm-project/llvm/lib/MC/MCParser/AsmParser.cpp:2323:47
#18 0x000000000597444c (anonymous namespace)::AsmParser::Run(bool, bool) /data/home/bennshi/work/llvm-project/llvm/lib/MC/MCParser/AsmParser.cpp:1005:33
#19 0x0000000002a3e5a0 llvm::AsmPrinter::emitInlineAsm(llvm::StringRef, llvm::MCSubtargetInfo const&, llvm::MCTargetOptions const&, llvm::MDNode const*, llvm::InlineAsm::AsmDialect) const /data/home/bennshi/work/llvm-project/llvm/lib/CodeGen/AsmPrinter/AsmPrinterInlineAsm.cpp:131:39
#20 0x0000000002a3fab8 llvm::AsmPrinter::emitInlineAsm(llvm::MachineInstr const*) const /data/home/bennshi/work/llvm-project/llvm/lib/CodeGen/AsmPrinter/AsmPrinterInlineAsm.cpp:418:16
#21 0x0000000002a05189 llvm::AsmPrinter::emitFunctionBody() /data/home/bennshi/work/llvm-project/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp:1862:9
#22 0x00000000025add1c llvm::AsmPrinter::runOnMachineFunction(llvm::MachineFunction&) /data/home/bennshi/work/llvm-project/llvm/include/llvm/CodeGen/AsmPrinter.h:390:12
#23 0x0000000002e2c653 llvm::MachineFunctionPass::runOnFunction(llvm::Function&) /data/home/bennshi/work/llvm-project/llvm/lib/CodeGen/MachineFunctionPass.cpp:94:33
#24 0x0000000003619ec1 llvm::FPPassManager::runOnFunction(llvm::Function&) /data/home/bennshi/work/llvm-project/llvm/lib/IR/LegacyPassManager.cpp:1406:20
#25 0x000000000361a10a llvm::FPPassManager::runOnModule(llvm::Module&) /data/home/bennshi/work/llvm-project/llvm/lib/IR/LegacyPassManager.cpp:1452:13
#26 0x000000000361a4c4 (anonymous namespace)::MPPassManager::runOnModule(llvm::Module&) /data/home/bennshi/work/llvm-project/llvm/lib/IR/LegacyPassManager.cpp:1521:20
#27 0x0000000003615e43 llvm::legacy::PassManagerImpl::run(llvm::Module&) /data/home/bennshi/work/llvm-project/llvm/lib/IR/LegacyPassManager.cpp:539:13
#28 0x000000000361ac87 llvm::legacy::PassManager::run(llvm::Module&) /data/home/bennshi/work/llvm-project/llvm/lib/IR/LegacyPassManager.cpp:1649:1
#29 0x0000000001f9f5da compileModule(char**, llvm::LLVMContext&) /data/home/bennshi/work/llvm-project/llvm/tools/llc/llc.cpp:753:34
#30 0x0000000001f9d009 main /data/home/bennshi/work/llvm-project/llvm/tools/llc/llc.cpp:411:35
#31 0x00007fedec7b8d85 __libc_start_main ../csu/libc-start.c:336:3
#32 0x0000000001f9bdae _start (./bin/llc+0x1f9bdae)
Aborted (core dumped)

[benshi001]

It is strange that at /data/home/bennshi/work/llvm-project/llvm/lib/Target/AVR/MCTargetDesc/AVRInstPrinter.cpp,

MOI.RegClass is AVR::PTRREGSRegClassID while Op.getReg() is R26 than expected X.

[workingjubilee]

Noteworthy is the original code looks like this in Rust:

let target: *mut u8 = 0x0025 as *mut u8;
let value: u8 = 0;
unsafe {
    asm!(
        "st {port}, {value}",
        port = in(reg_ptr) target,
        value = in(reg) value,
    );
}

And gives this disassembly:

main:                                   ; @main
; %bb.0:
	ldi	r26, 37
	ldi	r27, 0
	st	(?), r1

But when this was used:

unsafe {
    asm!(
        "st X, {value}",
        in("X") target,
        value = in(reg) value,
    );
}

The programmer got the desired behavior:

00000080 <main>:
  80:	a5 e2       	ldi	r26, 0x25	; 37
  82:	b0 e0       	ldi	r27, 0x00	; 0
  84:	1c 92       	st	X, r1

I believe reg_ptr is supposed to match the e constraint for AVR so that either X, Y, or Z could be used in a manner that LLVM deems fit?

[benshi001]

@workingjubilee I have made a patch, which should have fixed this bug, could please have a try if it works in your rust-lang project ?

#118279