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movw.S
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/
movw.S
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/* https://cirosantilli.com/linux-kernel-module-cheat#arm-movw-and-movt-instructions */
#include <lkmc.h>
LKMC_PROLOGUE
/* movt (top) and movw (TODO what is w) set the higher
* and lower 16 bits of the register.
*/
movw r0, 0xFFFF
movt r0, 0x1234
add r0, 1
LKMC_ASSERT_EQ(r0, =0x12350000)
/* movw also zeroes out the top bits, allowing small 16-bit
* C constants to be assigned in a single instruction.
*
* It differs from mov because mov can only encode 8 bits
* at a time, while movw can encode 16.
*
* movt does not modify the lower bits however.
*/
ldr r0, =0x12345678
movw r0, 0x1111
LKMC_ASSERT_EQ(r0, =0x00001111)
LKMC_EPILOGUE