Error impossible constraint in asm

The constraints are single letters (possibly with extra decorations), and you can specify several alternatives (i.e., an inmediate operand or register is «ir»). So the constraint «eax» means constraints «e» (signed 32-bit integer constant), «a» (register eax), or «x» (any SSE register). That is a bit different that what OP meant… and output to an «e» clearly doesn’t make any sense. Also, if some operand (in this case an input and an output) must be the same as another, you refer to it by a number constraint. There is no need to say eax will be clobbered, it is an output. You can refer to the arguments in the inline code by %0, %1, …, no need to use explicit register names. So the correct version for the code as intended by OP would be:

#include <stdio.h>

int main(void)
{
    int foo=10, bar=15;

    __asm__ __volatile__ (
        "addl %2, %0"
        : "=a" (foo)
        : "0" (foo), "b" (bar)
    );

    printf("foo = %d", foo);

    return 0;
}

A better solution would be to allow %2 to be anything, and %0 a register (as x86 allows, but you’d have to check your machine manual):

#include <stdio.h>

int main(void)
{
    int foo=10, bar=15;

    __asm__ __volatile__ (
        "addl %2, %0"
        : "=r" (foo)
        : "0" (foo), "g" (bar)
    );

    printf("foo = %d", foo);

    return 0;
}

Get a error: impossible constraint in ‘asm’? #79

I get a error: impossible constraint in ‘asm’. it looks like some asm code can’t be used in NDK(just guess)? i found that the error occur in below, Anyone has this error before?
static inline void cpuid(uint32_t *eax, uint32_t *ebx, uint32_t *ecx, uint32_t *edx)
<
#ifndef _MSC_VER
uint32_t a = *eax, b, c, d;
asm volatile ( «cpuidnt» : «+a»(a), «=b»(b), «=c»(c), «=d»(d) );

*eax = a;
*ebx = b;
*ecx = c;
*edx = d;
#else
uint32_t cpuInfo[4];
__cpuid(cpuInfo, *eax);
*eax = cpuInfo[0];
*ebx = cpuInfo[1];
*ecx = cpuInfo[2];
*edx = cpuInfo[3];
#endif
>

The text was updated successfully, but these errors were encountered:

@amazingyyc There is some related discussion in issue #74. Many people have same problem as yours. You are not alone.

Hope the developers fix it asap!

I think the reason is that: a asm code «asm volatile ( «cpuidnt» : «+a»(a), «=b»(b), «=c»(c), «=d»(d) );» in file simd.h is not supported in ARM. so annotation the function(TH_API void THVector_(vectorDispatchInit)();) in file TH/generic/THVector.h and file THVectorDispatch.c. it will work well.

the above method is not fit the «torch-android». But works well in my own Android project that just include torch/TH and torch/THNN.
But I got another question: my own build project is very very slower than other ‘s. Should I set any parameter in my own building? @BrianOn99

@amazingyyc I am not an a developer here. I have never been able to run the demo app. If it is possible, would you mind share how you build the app? (Did you success?)

Nevertheless, I could give you some suggestion. Some one has integrated openblas to torch-android: #68. See if that can help you!

[Edit]
Sorry I may have misunderstood your question. Did you mean your building process is slow or your app is slow?

thank u for your apply. I do not run this demo app successfully either. I just run the only troch/TH and torch/THNN on android(the core of torch). The method has been mentioned: annotation the code «asm volatile ( «cpuidnt» : «+a»(a), «=b»(b), «=c»(c), «=d»(d) );»..
By the way thank u for your advice about the openblas.

I had a similar error. I resolved it by adding NEON_FOUND flash to true in the build script so that it builds for neon platform.
I have updated both this repo and NVIDIA location, please try the trick above.

Thanks @borisfom. May I ask could the sample apps be build and run successfully now (without CUDA)?

my app is slow compared other’s THNN.so like prisma (the prisma app using the thnn too).

update the code and the problem is gone(i do not know why)?!
But got another problem: error: ‘THHalfVector_fill_DISPATCHTABLE’ undeclared (first use in this function) #define THVector_(NAME) TH_CONCAT_4(TH,Real,Vector_,NAME)
I feel the world is going to dark 😩

@amazingyyc Yeah, I have already opened the issue #78.
The «HalfVector» stuff are added for the CUDA backend, but it should be optional.

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Compilation error with 4.14 kernel: «impossible constraint in asm» #50

Trying to compile the latest isgx module from the master branch:

I see this error on both Fedora 27 and Arch Linux.

The text was updated successfully, but these errors were encountered:

This seems to be a recurrence of #13, and even has the same workaround.

So I understand that the only difference is the addition of M=$(PWD) instead of SUBDIRS=$(PWD) in the original Makefile.
Can we close it?

I have been working around this problem by removing the -O0 option from CFLAGS_MODULE in the Makefile . I would consider closing it without an attempt at understanding it to be premature.

I ran into similiar problems when compiling kernel 4.14 by changing -O2 to -O0.

`In file included from ./include/linux/compiler_types.h:58:0,
from ./include/linux/compiler.h:5,
from ./arch/x86/include/asm/atomic.h:5,
from ./include/linux/atomic.h:5,
from ./include/linux/crypto.h:20,
from arch/x86/kernel/asm-offsets.c:9:
./arch/x86/include/asm/cpufeature.h: In function ‘_static_cpu_has’:
./include/linux/compiler-gcc.h:270:38: warning: asm operand 0 probably doesn’t match constraints
#define asm_volatile_goto(x. ) do < asm goto(x); asm («»); >while (0)
^
./arch/x86/include/asm/cpufeature.h:148:3: note: in expansion of macro ‘asm_volatile_goto’
asm_volatile_goto(«1: jmp 6fn»
^
./include/linux/compiler-gcc.h:270:38: warning: asm operand 2 probably doesn’t match constraints
#define asm_volatile_goto(x. ) do < asm goto(x); asm («»); >while (0)
^
./arch/x86/include/asm/cpufeature.h:148:3: note: in expansion of macro ‘asm_volatile_goto’
asm_volatile_goto(«1: jmp 6fn»

./include/linux/compiler-gcc.h:270:38: error: impossible constraint in ‘asm’
#define asm_volatile_goto(x. ) do < asm goto(x); asm («»); >while (0)
^
./arch/x86/include/asm/cpufeature.h:148:3: note: in expansion of macro ‘asm_volatile_goto’
asm_volatile_goto(«1: jmp 6fn»
^`

The trouble above was caused by extended assembly in arch/x86/include/asm/cpufeature.h, where the modifiers of the operand 0 and 2 were i, meaning that immediate integers were expected. But they both used parameter bit, which was a variable instead of a constant. If -O2 was specified, the inline function _static_cpu_has was expanded with a constant in place of parameter bit, which bypassed the restriction.

static __always_inline __pure bool _static_cpu_has(u16 bit) < asm_volatile_goto(«1: jmp 6fn» «2:n» «.skip -(((5f-4f) — (2b-1b)) >0) * » «((5f-4f) — (2b-1b)),0x90n» «3:n» «.section .altinstructions,»a»n» » .long 1b — .n» /* src offset */ » .long 4f — .n» /* repl offset */ » .word %P1n» /* always replace */ » .byte 3b — 1bn» /* src len */ » .byte 5f — 4fn» /* repl len */ » .byte 3b — 2bn» /* pad len */ «.previousn» «.section .altinstr_replacement,»ax»n» «4: jmp %l[t_no]n» «5:n» «.previousn» «.section .altinstructions,»a»n» » .long 1b — .n» /* src offset */ » .long 0n» /* no replacement */ » .word %P0n» /* feature bit */ » .byte 3b — 1bn» /* src len */ » .byte 0n» /* repl len */ » .byte 0n» /* pad len */ «.previousn» «.section .altinstr_aux,»ax»n» «6:n» » testb %[bitnum],%[cap_byte]n» » jnz %l[t_yes]n» » jmp %l[t_no]n» «.previousn» : : **»i» (bit)**, «i» (X86_FEATURE_ALWAYS), **[bitnum] «i» (1 > 3]) : : t_yes, t_no); t_yes: return true; t_no: return false; >

Источник

asm impossible constraint #3

I get the following error, while running:

$ make
.
make[4]: Entering directory ‘/home/july/msed/syslinux/gpxe/src’ [BUILD] bin/int13.o arch/i386/interface/pcbios/int13.c: In function ‘register_int13_drive’: arch/i386/interface/pcbios/int13.c:469:2: warning: asm operand 0 probably doesn’t match constraints __asm__ __volatile__ ( ^ arch/i386/interface/pcbios/int13.c:469:2: error: impossible constraint in ‘asm’ bin/deps/arch/i386/interface/pcbios/int13.c.d:86: recipe for target ‘bin/int13.o’ failed make[4]: *** [bin/int13.o] Error 1

My build env is:
$ nasm -v
NASM version 2.11.08 compiled on Mar 24 2015

$ gcc -v
Using built-in specs.

Configured with: /build/gcc-multilib/src/gcc-5.3.0/configure —prefix=/usr —libdir=/usr/lib —libexecdir=/usr/lib —mandir=/usr/share/man —infodir=/usr/share/info —with-bugurl=https://bugs.archlinux.org/ —enable-languages=c,c++,ada,fortran,go,lto,objc,obj-c++ —enable-shared —enable-threads=posix —enable-libmpx —with-system-zlib —with-isl —enable-__cxa_atexit —disable-libunwind-exceptions —enable-clocale=gnu —disable-libstdcxx-pch —disable-libssp —enable-gnu-unique-object —enable-linker-build-id —enable-lto —enable-plugin —enable-install-libiberty —with-linker-hash-style=gnu —enable-gnu-indirect-function —enable-multilib —disable-werror —enable-checking=release

Thread model: posix

gcc version 5.3.0 (GCC)

Built for x86_64-unknown-linux-gnu

Linux stoffle 4.3.3-3-ARCH #1 SMP PREEMPT Wed Jan 20 08:12:23 CET 2016 x86_64 GNU/Linux

I’m running Arch Linux, so all the tools are the latest versions of respective tools.

I’m not an expert of asm constraints, but I did a couple of changes in order to complete the make process (see the patch file). I assume, those changes might be wrong (EDIT: are wrong — see my next comment).
asm_constraints.patch.zip

The text was updated successfully, but these errors were encountered:

Источник

Compilation error with g++: impossible register constraint in ‘asm’ #554

Hello, I’m experiencing a compilation error with master, commit 1a7f19c.

I’ve tried dropping to -O2 as suggested in #553 but it does not fix the error.

I just compiled with make and the compilation aborted in gcm-simd.cpp . Here is the error

I’m running Red-Hat 6.7 and the compilers I have are

The text was updated successfully, but these errors were encountered:

Thanks @EduardoMiravalls . And sorry about things.

error: impossible register constraint in ‘asm’

Yeah, I’ve seen that before. Here’s the ASM, and there’s not much to it. Below is from gcm-simd.cpp :

The constraint it is talking about is the part : «=m» (a[0]) : «xm»(b[0]), «xm»(c[0])); . The x is a SSE register, and the m is memory. I wonder if two memory expressions is giving the older tool chain problems. Or maybe, the toolchain wants the output constraint to be xm .

Give me some time to find a machine with GCC 4.4. I think I have one somewhere.

I believe CentOS 5 comes with g++ 4.4.7, maybe you can use it in a vm?

OK, going back to Wei’s code before we started fiddling with things:

I was able to duplicate it with CentOS 5 (Binutils 2.17). This clears the issue under CentOS:

I’m going to check-in the one shown above with output operand of xm . The GCC folks tell us to provide GCC with as many alternatives as possible, so we are consistent with their best practices. But keep in mind that’s what got us into trouble in the first place — we added additional constraints to give the inline assembler a more choices 😮

Ugh, this broke GCC 4.8/4.9 on Core2’s:

Mind if I ask why did it specifically affect Core2s?
FYI, I’ve just pulled your latest commits and it compiles OK on my setup.

Mind if I ask why did it specifically affect Core2s?

The Core2 machine is what I have for testing on real hardware. The issue probably affects other machines, too. It is likely tied to a few versions of Binutils, which supplies the assembler.

I also have older machines that predate the Core2. They include PIII’s and P4’s. They probably suffer it too when the assembler version is just right. I test less frequently on them because they are slow.

Источник

Building

syslinux-6.04_pre1 fails to build on gcc-10 due to -fno-common change; gcc-10 (and above) flipped a default, from -fcommon to -fno-common.

gcc-10 will reject multiple definitions of global variables. Possible/potential workaround: add/append -fcommon to CFLAGS. Ideally, the code would need a few ‘extern‘ additions and maybe moving variable definitions.

Patches already included in Syslinux 6.04-pre1 (released 2016Mar):

Testing Syslinux 6.04-pre1 (or later) is recommended.

Источник

I ran into similiar problems when compiling kernel 4.14 by changing -O2 to -O0.

`In file included from ./include/linux/compiler_types.h:58:0,
from ./include/linux/compiler.h:5,
from ./arch/x86/include/asm/atomic.h:5,
from ./include/linux/atomic.h:5,
from ./include/linux/crypto.h:20,
from arch/x86/kernel/asm-offsets.c:9:
./arch/x86/include/asm/cpufeature.h: In function ‘_static_cpu_has’:
./include/linux/compiler-gcc.h:270:38: warning: asm operand 0 probably doesn’t match constraints
#define asm_volatile_goto(x…) do { asm goto(x); asm («»); } while (0)
^
./arch/x86/include/asm/cpufeature.h:148:3: note: in expansion of macro ‘asm_volatile_goto’
asm_volatile_goto(«1: jmp 6fn»
^
./include/linux/compiler-gcc.h:270:38: warning: asm operand 2 probably doesn’t match constraints
#define asm_volatile_goto(x…) do { asm goto(x); asm («»); } while (0)
^
./arch/x86/include/asm/cpufeature.h:148:3: note: in expansion of macro ‘asm_volatile_goto’
asm_volatile_goto(«1: jmp 6fn»

./include/linux/compiler-gcc.h:270:38: error: impossible constraint in ‘asm’
#define asm_volatile_goto(x…) do { asm goto(x); asm («»); } while (0)
^
./arch/x86/include/asm/cpufeature.h:148:3: note: in expansion of macro ‘asm_volatile_goto’
asm_volatile_goto(«1: jmp 6fn»
^`

The trouble above was caused by extended assembly in arch/x86/include/asm/cpufeature.h, where the modifiers of the operand 0 and 2 were i, meaning that immediate integers were expected. But they both used parameter bit, which was a variable instead of a constant. If -O2 was specified, the inline function _static_cpu_has was expanded with a constant in place of parameter bit, which bypassed the restriction.

static __always_inline __pure bool _static_cpu_has(u16 bit) { asm_volatile_goto("1: jmp 6fn" "2:n" ".skip -(((5f-4f) - (2b-1b)) > 0) * " "((5f-4f) - (2b-1b)),0x90n" "3:n" ".section .altinstructions,"a"n" " .long 1b - .n" /* src offset */ " .long 4f - .n" /* repl offset */ " .word %P1n" /* always replace */ " .byte 3b - 1bn" /* src len */ " .byte 5f - 4fn" /* repl len */ " .byte 3b - 2bn" /* pad len */ ".previousn" ".section .altinstr_replacement,"ax"n" "4: jmp %l[t_no]n" "5:n" ".previousn" ".section .altinstructions,"a"n" " .long 1b - .n" /* src offset */ " .long 0n" /* no replacement */ " .word %P0n" /* feature bit */ " .byte 3b - 1bn" /* src len */ " .byte 0n" /* repl len */ " .byte 0n" /* pad len */ ".previousn" ".section .altinstr_aux,"ax"n" "6:n" " testb %[bitnum],%[cap_byte]n" " jnz %l[t_yes]n" " jmp %l[t_no]n" ".previousn" : : **"i" (bit)**, "i" (X86_FEATURE_ALWAYS), **[bitnum] "i" (1 << (bit & 7)),** [cap_byte] "m" (((const char *)boot_cpu_data.x86_capability)[bit >> 3]) : : t_yes, t_no); t_yes: return true; t_no: return false; }

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This article was updated on 2023-02-03 and previously published under WIKI_Q210794

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__attribute__((naked)) static return_type signature 
{ 
__asm( 
"svc %0n" 
"bx r14" : : "I" (number) : "r0" 
); 
}

error: impossible constraint in 'asm'

Решение

#define syscall(number) __attribute__((naked)) static return_type signature 
{ 
__asm( 
"svc " #number "n" 
"bx r14" : : : "r0" 
); 
}

Другие решения

Модератор: Модераторы разделов

inline Atomic32 NoBarrier_CompareAndSwap(volatile Atomic32* ptr,
                                         Atomic32 old_value,
                                         Atomic32 new_value) {
  Atomic32 prev, tmp;
  __asm__ __volatile__(".set pushn"
                       ".set noreordern"
                       "1:n"
                       "ll %0, %5n"  // prev = *ptr
                       "bne %0, %3, 2fn"  // if (prev != old_value) goto 2
                       "move %2, %4n"  // tmp = new_value
                       "sc %2, %1n"  // *ptr = tmp (with atomic check)
                       "beqz %2, 1bn"  // start again on atomic error
                       "nopn"  // delay slot nop
                       "2:n"
                       ".set popn"
                       : "=&r" (prev), "=m" (*ptr), "=&r" (tmp)
                       : "Ir" (old_value), "r" (new_value), "m" (*ptr)
                       : "memory"); // 69 строка
  return prev;
}

# sh4-linux-g++ --version
sh4-linux-g++ (GCC) 4.2.4 (snapshot) (STMicroelectronics/Linux Base 4.2.4-52)