I am looking into optimizing the fast_increment_function in Zend/zend-operators.h for better performance on aarch64 systems by adding some inline assembly that will reproduce what currently exists for x86_64 and i386 systems.
My main issue at the moment is understanding what occurs in the x86_64 assembly section when the incremented register overflows. I understand that it moves a some constant values into the registers, but I don't understand the significance of these values or why we use them. __asm__( "incq (%0)\n\t" "jno 0f\n\t" "movl $0x0, (%0)\n\t" "movl $0x43e00000, 0x4(%0)\n\t" "movb %1, %c2(%0)\n" "0:" : : "r"(&op1->value), "n"(IS_DOUBLE), "n"(ZVAL_OFFSETOF_TYPE) : "cc"); Can anyone clarify the purpose of the 3 'mov' instructions? Thanks, Justin
