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"Additionally, code that handles 32-bit registers in x86_64 is often shorter than its 64-bit counterpart due to the lack of REX prefixes in instructions." Exce
by cgh 12y ago
"Additionally, code that handles 32-bit registers in x86_64 is often shorter than its 64-bit counterpart due to the lack of REX prefixes in instructions."
Excellent point, thank you. I was only thinking about the data cache. Interestingly, I believe 64-bit ARM (AArch64) instructions are still only 32 bits long though I haven't confirmed via google. Maybe someone can correct me.
- jfpoole 12y agoAArch64 instructions are still 32 bits long. These slides from the ARMv8 Technology Preview provide a great overview of the ARMv8 architecture: http://www.arm.com/files/downloads/ARMv8_Architecture.pdf http://www.arm.com/files/downloads/ARMv8_Architecture.pdf
- stephencanon 12y ago> I believe 64-bit ARM (AArch64) instructions are still only 32 bits long Correct, but I wouldn’t say “still”, since some “thumb” AArch32 instructions are 16b.