Date: Wed, 27 Nov 2002 14:43:44 +1100 From: Peter Jeremy <peter.jeremy@alcatel.com.au> To: Poul-Henning Kamp <phk@critter.freebsd.dk> Cc: alpha@FreeBSD.ORG Subject: Re: ev4/5/6 issue ? Message-ID: <20021127034344.GB77914@gsmx07.alcatel.com.au> In-Reply-To: <54463.1037022613@critter.freebsd.dk> References: <15823.46162.102126.470628@grasshopper.cs.duke.edu> <54463.1037022613@critter.freebsd.dk>
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[Somewhat old but I don't think these points were ever answered] On 2002-Nov-11 14:50:13 +0100, Poul-Henning Kamp <phk@critter.freebsd.dk> wrote: >If this is an ev45/ev6 issue I guess my very naïve end-user questions >are: > > 1. Why doesn't file(1) tell me if a binary is ev45 or ev6 ? For much the same reason it doesn't tell you that the binary is a K-7 rather than 80386. These are just code generation options on the compiler. This isn't as noticable on x86 because gcc doesn't tend to use instructions that don't exist on the 386 (apart from FP). I guess that in theory the compiler/assembler could output an ELF option giving a bitmap of which instruction groups it emitted, from which the linker could generate a merged bitmap showing which instruction groups are needed by the executable (modulo dynamic linker issues). This sounds like a fair amount of work and it's not clear that there's much benefit. > 2. Couldn't the elf activator not find out and say "Sorry, > cannot execute ev6 on this machine" ? If there was some easy way for the ELF activator to know that executable file contained EV6-specific instructions and the current CPU didn't support them, then this could possibly be useful. Given that we have emulation support for some instructions, what should the ELF activator do if an executable requires an instruction that doesn't exist in the CPU hardware, but is emulated? If that instruction is only executed once or twice, the user wouldn't even notice it was emulated. OTOH, if it formed the core of one of the innermost loops, the difference is probably quite important. Peter
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