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add better inline assembler example
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@ -406,25 +406,29 @@ The result, as expected:
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All of these constraints may be combined (so long as they do not conflict). In this case the compiler will choose the best one for a certain situation. For example:
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All of these constraints may be combined (so long as they do not conflict). In this case the compiler will choose the best one for a certain situation. For example:
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```C
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```C
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#include <stdio.h>
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unsigned long a = 10;
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unsigned long b = 20;
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unsigned long a = 1;
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void main(void)
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int main(void)
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{
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{
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unsigned long b;
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__asm__ ("movq %1,%0" : "=mr"(b) : "rm"(a));
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__asm__ ("movq %1,%0" : "=r"(b) : "r"(a));
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return b;
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}
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}
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```
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```
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will use a memory operand:
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will use a memory operand:
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```assembly
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```assembly
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0000000000400400 <main>:
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main:
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4004aa: 48 8b 05 6f 0b 20 00 mov 0x200b6f(%rip),%rax # 601020 <a>
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movq a(%rip),b(%rip)
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ret
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b:
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.quad 20
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a:
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.quad 10
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```
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```
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instead of direct usage of general purpose registers.
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That's about all of the commonly used constraints in inline assembly statements. You can find more in the official [documentation](https://gcc.gnu.org/onlinedocs/gcc/Simple-Constraints.html#Simple-Constraints).
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That's about all of the commonly used constraints in inline assembly statements. You can find more in the official [documentation](https://gcc.gnu.org/onlinedocs/gcc/Simple-Constraints.html#Simple-Constraints).
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Architecture specific constraints
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Architecture specific constraints
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