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Re: [Qemu-devel] Add ARM920T to ARM emulation
From: |
Paul Brook |
Subject: |
Re: [Qemu-devel] Add ARM920T to ARM emulation |
Date: |
Fri, 29 May 2009 23:05:28 +0100 |
User-agent: |
KMail/1.11.2 (Linux/2.6.29-2-amd64; KDE/4.2.2; x86_64; ; ) |
> There was some discussion of the differences between v4 and v5 with
> respect to LDR behaviour manipulating the program counter when the
> bottom bit of an adress is set. The ARM-ARM clearly defines such
> behaviour as "unpredicatble" (section A2.4.3 page 48) where it says
> "In all variants of ARMv4 and ARMv5, bits[1:0] of a value written to
> R15 in ARM state must be 0b00. If they are not, the results are
> UNPREDICTABLE." .
This statement is only applies to instructions that do not have explicit
semantics for r15. Use of r15 as a destination in load/pop instructions is
well defined.
Paul