From: Mike Frysinger <vapier@gentoo.org>
To: Nicholas Clifton <nickc@redhat.com>
Cc: gdb-patches@sourceware.org
Subject: Re: RFA: AArch64 sim
Date: Tue, 10 Nov 2015 07:32:00 -0000 [thread overview]
Message-ID: <20151110073245.GN5154@vapier.lan> (raw)
In-Reply-To: <55A90CBA.40007@redhat.com>
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On 17 Jul 2015 15:10, Nicholas Clifton wrote:
> >> +++ include/gdb/sim-aarch64.h
>
> >> +#ifdef __cplusplus
> >> +extern "C" { // }
> >> +#endif
> >
> > hmm, i see a few arches do this, but most don't. is there any reason we should
> > keep this ? or should we scrub all targets to not do this ?
>
> It is your call. I saw that other header files in this directory were
> doing it, so I thought that it would be wise to follow their example.
> The extra code does not hurt when compiling with C and I presume that it
> is necessary when compiling with C++. (I do not know this for sure
> though - I hate C++). I am happy to remove the code if you want however.
i've posted a patch to clean up the others. you should trim it from this
one in the meantime.
> >> +typedef enum
> >> +{
> >> + STATUS_READY = 0, /* May continue stepping or running. */
> >> + STATUS_RETURN = 1, /* Via normal return from initial frame. */
> >> + STATUS_HALT = 2, /* Via HALT pseudo-instruction. */
> >> + STATUS_BREAK = 3, /* Via BRK instruction. */
> >> + STATUS_CALLOUT = 4, /* Via CALLOUT pseudo-instruction. */
> >> + STATUS_ERROR = 5, /* Simulator detected problem. */
> >> + STATUS_MAX = 6
> >> +} StatusCode;
> >
> > a scan of the code indicates that most of this looks like you're setting state
> > and then acting on it later yourself when you really should be calling
> > sim_engine_halt directly. any reason for doing it this way ?
>
> Originally it was simply historical - this is the way the code was
> written in the smallaarch64sim. Now it is because it allows better
> tracing and disassembler output, and cleaner code - the halt and error
> returns are only handled in one place.
i'm not seeing how this is cleaner. when you call sim_engine_halt, the
code stops at that point. there is no returning/etc... afterwards.
plus, when i look at some of these funcs, they only ever return READY.
which leads to a lot of return code paths that are pointless.
+#define STORE_FUNC(TYPE, NAME, N) \
+ StatusCode \
+ aarch64_set_mem_##NAME (sim_cpu *cpu, uint64_t address, TYPE value) \
+ { \
+ TRACE_MEMORY (cpu, \
+ "write of %" PRIx64 " (%d bytes) to %" PRIx64, \
+ (uint64_t) value, N, address); \
+ \
+ sim_core_write_unaligned_##N (cpu, 0, write_map, address, value); \
+ return STATUS_READY; \
+ }
...
+static StatusCode
+stur32 (sim_cpu *cpu, int32_t offset)
+{
+ unsigned rn = uimm (cpu->instr, 9, 5);
+ unsigned rd = uimm (cpu->instr, 4, 0);
+
+ return aarch64_set_mem_u32 (cpu,
+ aarch64_get_reg_u64 (cpu, rn, SP_OK) + offset,
+ aarch64_get_reg_u32 (cpu, rd, NO_SP));
+}
...
+static StatusCode
+dexLoadUnscaledImmediate (sim_cpu *cpu)
... i scanned a bunch of these and they look like above ...
+ case 0: return sturb (cpu, imm);
+ case 1: return ldurb32 (cpu, imm);
+ case 2: return ldursb64 (cpu, imm);
+ case 3: return ldursb32 (cpu, imm);
+ case 4: return sturh (cpu, imm);
+ case 5: return ldurh32 (cpu, imm);
+ case 6: return ldursh64 (cpu, imm);
+ case 7: return ldursh32 (cpu, imm);
+ case 8: return stur32 (cpu, imm);
+ case 9: return ldur32 (cpu, imm);
+ case 10: return ldursw (cpu, imm);
+ case 12: return stur64 (cpu, imm);
+ case 13: return ldur64 (cpu, imm);
...
in this func, the only thing that doesn't return READY are:
+ return_NYI;
+ return_UNALLOC;
which look like:
+#define return_UNALLOC \
+ do \
+ { \
+ if (TRACE_INSN_P (cpu)) \
+ { \
+ aarch64_print_insn (CPU_STATE (cpu), aarch64_get_PC (cpu)); \
+ TRACE_INSN (cpu, \
+ "Unallocated instruction detected at sim line %d,"\
+ " exe addr %" PRIx64, \
+ __LINE__, aarch64_get_PC (cpu)); \
+ } \
+ cpu->errorCode = ERROR_UNALLOC; \
+ return STATUS_ERROR; \
+ } \
+ while (1)
so instead of returning, just call sim_engine_halt directly
in fact, i only see the errorCode field being set. nowhere is it being
read. you might think "wait but there's aarch64_get_ErrorCode and
aarch64_get_error_text" ... except nothing calls those functions.
so i can't see how errorCode adds any value, just noise, nor does it have
any impact on debugging/tracing output.
> Is this version OK to apply ?
you should scan the files and trim trailing whitespace while you're at it.
sed -i -r 's:[[:space:]]+$::' *.[ch]
-mike
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next prev parent reply other threads:[~2015-11-10 7:32 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-06-28 12:25 Nick Clifton
2015-07-02 9:17 ` Andre Vieira
2015-07-02 13:53 ` Nicholas Clifton
2015-07-02 14:43 ` Andre Vieira
[not found] ` <55954DEE.50609@arm.com>
2015-07-02 15:20 ` Nicholas Clifton
2015-07-07 17:12 ` Mike Frysinger
2015-07-15 16:58 ` Nick Clifton
2015-07-16 15:19 ` Mike Frysinger
2015-07-17 14:10 ` Nicholas Clifton
2015-11-10 7:32 ` Mike Frysinger [this message]
2015-11-19 14:51 ` Nick Clifton
2015-11-20 9:13 ` Mike Frysinger
2015-11-20 10:56 ` Nick Clifton
2015-11-20 19:28 ` Mike Frysinger
2015-11-24 8:50 ` Nick Clifton
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