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Pettenò: Debunking x32 mythsPettenò: Debunking x32 mythsPosted Jun 26, 2012 11:07 UTC (Tue) by k3ninho (subscriber, #50375)In reply to: Pettenò: Debunking x32 myths by butlerm Parent article: Pettenò: Debunking x32 myths
>If x32 is useful, something similar for ARM 64-bit is likely to be useful for exactly the same reason.
This is what Thumb[1] already does for 16-bit code in a 32-bit processor (well, it actually cuts down the instructions as well as the data to 16-bit symbols, and initially restricted the functionality to subset of the ARMv4 IA). I have no idea what Thumb-like behaviour would be included in a 64-bit ARM IA.
1: http://en.wikipedia.org/wiki/ARM_architecture#Thumb
K3n.
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Pettenò: Debunking x32 myths Posted Jun 26, 2012 11:47 UTC (Tue) by mansr (guest, #85328) [Link]
> [Thumb] cuts down the instructions as well as the data to 16-bit symbols
Wrong. The original Thumb instruction set has 16-bit instructions with reduced functionality, most notably many instructions can access only the low 8 registers. The register size is still 32 bits. Thumb2 extends the instruction set with additional 32-bit instructions providing full access to the entire architecture.
The 64-bit ARM has no equivalent of Thumb mode, although 32-bit ARMv7 userspace is still supported.
See http://www.arm.com/files/downloads/ARMv8_Architecture.pdf for more information.
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