[llvm-dev] pointer arithmetic with address space attribute not working

Wed Oct 30 19:03:15 PDT 2019

I forgot the -DADD flag earlier but the result did not change: https://godbolt.org/z/NPcn22

________________________________________
From: llvm-dev <llvm-dev-bounces at lists.llvm.org> on behalf of Doerfert, Johannes via llvm-dev <llvm-dev at lists.llvm.org>
Sent: Wednesday, October 30, 2019 20:18
To: LLVM Developers Mailing List; Y Song
Cc: Alexei Starovoitov
Subject: Re: [llvm-dev] pointer arithmetic with address space attribute not     working

What clang version is that?
I tried to reproduce it but failed: https://godbolt.org/z/AM1tPp

________________________________________
From: llvm-dev <llvm-dev-bounces at lists.llvm.org> on behalf of Y Song via llvm-dev <llvm-dev at lists.llvm.org>
Sent: Wednesday, October 30, 2019 17:56
To: LLVM Developers Mailing List
Cc: Alexei Starovoitov
Subject: [llvm-dev] pointer arithmetic with address space attribute not working

Hi,

I have a case that for pointer with address space attribute, pointer
arithmetic is not work.

For example,
-bash-4.4$ cat test.c
#define __user __attribute__((address_space(1)))
void __user * test(void __user *arg) {
#ifdef ADD
  return arg + 4;
#else
  return arg;
#endif
}
-bash-4.4$

-bash-4.4$ clang -g -c test.c
-bash-4.4$ clang -g -c -DADD test.c
clang-10: ../lib/IR/Instructions.cpp:2749: static llvm::CastInst
*llvm::CastInst::Create(Instruction::CastOps, llvm::Value *,
llvm::Type *, const llvm::Twine
&, llvm::Instruction *): Assertion `castIsValid(op, S, Ty) && "Invalid
cast!"' failed.
Stack dump:
0.      Program arguments:
/data/users/yhs/work/llvm-project/llvm/build/install/bin/clang-10 -cc1
-triple x86_64-unknown-linux-gnu -emit-obj -mrelax-all -disa
ble-free -main-file-name test.c -mrelocation-model static
-mthread-model posix -mframe-pointer=all -fmath-errno -masm-verbose
-mconstructor-aliases -munwind-t
ables -fuse-init-array -target-cpu x86-64 -dwarf-column-info
-debug-info-kind=limited -dwarf-version=4 -debugger-tuning=gdb
-resource-dir /data/users/yhs/work
/llvm-project/llvm/build/install/lib/clang/10.0.0 -D ADD
-internal-isystem /usr/local/include -internal-isystem
/data/users/yhs/work/llvm-project/llvm/build/i
nstall/lib/clang/10.0.0/include -internal-externc-isystem /include
-internal-externc-isystem /usr/include -fdebug-compilation-dir
/home/yhs/work/tests/user -f
error-limit 19 -fmessage-length 0 -fgnuc-version=4.2.1
-fobjc-runtime=gcc -fdiagnostics-show-option -fcolor-diagnostics
-faddrsig -o test.o -x c test.c
1.      <eof> parser at end of file
2.      test.c:2:15: LLVM IR generation of declaration 'test'
3.      test.c:2:15: Generating code for declaration 'test'
 #0 0x00000000017067bf llvm::sys::PrintStackTrace(llvm::raw_ostream&)
(/data/users/yhs/work/llvm-project/llvm/build/install/bin/clang-10+0x17067bf)
 #1 0x0000000001704a50 llvm::sys::RunSignalHandlers()
(/data/users/yhs/work/llvm-project/llvm/build/install/bin/clang-10+0x1704a50)
 #2 0x0000000001706d28 SignalHandler(int)
(/data/users/yhs/work/llvm-project/llvm/build/install/bin/clang-10+0x1706d28)
 #3 0x00007fed0c6c3b10 __restore_rt
(/usr/local/fbcode/platform007/lib/libpthread.so.0+0x12b10)
 #4 0x00007fed0b81214f raise
(/usr/local/fbcode/platform007/lib/libc.so.6+0x3714f)
 #5 0x00007fed0b7fb935 abort
(/usr/local/fbcode/platform007/lib/libc.so.6+0x20935)
 #6 0x00007fed0b80a107 __assert_fail_base
(/usr/local/fbcode/platform007/lib/libc.so.6+0x2f107)
 #7 0x00007fed0b80a173 (/usr/local/fbcode/platform007/lib/libc.so.6+0x2f173)
 #8 0x00000000011b9381
llvm::CastInst::Create(llvm::Instruction::CastOps, llvm::Value*,
llvm::Type*, llvm::Twine const&, llvm::Instruction*) (/data/users/yhs/
work/llvm-project/llvm/build/install/bin/clang-10+0x11b9381)
 #9 0x0000000001b5177f
emitPointerArithmetic(clang::CodeGen::CodeGenFunction&, (anonymous
namespace)::BinOpInfo const&, bool) (/data/users/yhs/work/llvm-proje
ct/llvm/build/install/bin/clang-10+0x1b5177f)
#10 0x0000000001b42b86 clang::StmtVisitorBase<std::add_pointer,
(anonymous namespace)::ScalarExprEmitter,
llvm::Value*>::Visit(clang::Stmt*) (/data/users/yhs/
work/llvm-project/llvm/build/install/bin/clang-10+0x1b42b86)
#11 0x0000000001b3a245
clang::CodeGen::CodeGenFunction::EmitScalarExpr(clang::Expr const*,
bool) (/data/users/yhs/work/llvm-project/llvm/build/install/bin/cla
ng-10+0x1b3a245)
#12 0x00000000019226c8
clang::CodeGen::CodeGenFunction::EmitReturnStmt(clang::ReturnStmt
const&) (/data/users/yhs/work/llvm-project/llvm/build/install/bin/cla
ng-10+0x19226c8)

For pointer arithmetic failure, the clang tries to create a regular
pointer and failed since non-None address space is specified in the
type.

Is this a bug? Or this is the expected behavior? I am asking since
linux kernel has a lot of codes which did pointer arithmetic where
pointers have address space attributes. (currently those address
spaces are sparse tool checking only.)

Thanks,

Yonghong
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