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Hi,
I'm trying to find out the right way to pass an array variable as address into an Inline Assembly block as Input Constraint.
Test Program: #include <stdio.h>
int array[3] = {111, 222, 333};
int main(void) { int out = 0; asm( ".intel_syntax noprefix \n\t" "lea eax, %[array] \n\t" "mov eax,[eax] \n\t" "inc eax \n\t" ".intel_syntax prefix \n\t" : "=a" (out) : [array] "m" (*array) );
printf("out = %i\n", out);
return 0; }
Compiling on i386 machine, it worked: COMMAND LINE: gcc -fPIC -DPIC -masm=intel prog_i386 prog_i386.c
ASSEMBLY: mov %eax, DWORD PTR array@GOT[%ebx] #APP .intel_syntax noprefix lea eax, DWORD PTR [%eax]
Compiling on x86_64 machine, it didn't work: COMMAND LINE: gcc -fPIC -DPIC -masm=intel -o prog_x86_64 prog_x86_64.c
ERROR: /tmp/cc7z5OHz.s: Assembler messages: /tmp/cc7z5OHz.s:27: Error: invalid operand for 'mov' ('(' unexpected) /tmp/cc7z5OHz.s:38: Error: invalid operand for 'lea' ('(' unexpected)
ASSEMBLY: mov %rax, QWORD PTR array@GOTPCREL(%rip)
-- Daniel Yek.
#APP .intel_syntax noprefix lea rax, DWORD PTR [%rax]
I am hoping for a solution that is good for both compiling with -fPIC or not, if possible.
What is the right way to pass an array variable into Inline Assembly?
http://gcc.gnu.org/onlinedocs/gccint/Simple-Constraints.html#Simple-Constraints
Is there any other constraint that I should be using instead?
Thanks for your advice!
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