Re: [PATCH] x86: Use XORL r32,r32 in __get_user_asm

2020-08-27 Thread H. Peter Anvin
On 2020-08-27 09:49, Uros Bizjak wrote: > Use XORL r32,r32 for all operand sizes. x86_64 zero extends 32bit > operations, so for 64bit operands, XORL r32,r32 is functionally > equal to XORL r64,r64, but avoids a REX prefix byte when legacy > registers are used. Please make it clear that this refer

[PATCH] x86: Use XORL r32,r32 in __get_user_asm

2020-08-27 Thread Uros Bizjak
Use XORL r32,r32 for all operand sizes. x86_64 zero extends 32bit operations, so for 64bit operands, XORL r32,r32 is functionally equal to XORL r64,r64, but avoids a REX prefix byte when legacy registers are used. 32bit operation also avoids 0x66 size prefix for 16bit operands and REX prefix when