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Date: Wed, 11 May 2022 16:48:43 +0100
From: Bruce Richardson <bruce.richardson@intel.com>
To: Stanislaw Kardach <kda@semihalf.com>
Cc: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>, dev@dpdk.org,
 Frank Zhao <Frank.Zhao@starfivetech.com>,
 Sam Grove <sam.grove@sifive.com>, mw@semihalf.com, upstream@semihalf.com
Subject: Re: [PATCH v2 1/1] test/ring: remove excessive inlining
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References: <20220510115758.457794-1-kda@semihalf.com>
 <20220511150725.744021-1-kda@semihalf.com>
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On Wed, May 11, 2022 at 05:07:25PM +0200, Stanislaw Kardach wrote:
> Forcing inlining in test_ring_enqueue and test_ring_dequeue can cause
> the compiled code to grow extensively when compiled with no optimization
> (-O0 or -Og). This is default in the meson's debug configuration. This
> can collide with compiler bugs and cause issues during linking of unit
> tests where the api_type or esize are non-const variables causing
> inlining cascade. In perf tests this is not the case in perf-tests as
> esize and api_type are const values.
> 
> One such case was discovered when porting DPDK to RISC-V. GCC 11.2 (and
> no fix still in 12.1) is generating a short relative jump instruction
> (J <offset>) for goto and for loops. When loop body grows extensively in
> ring test, the target offset goes beyond supported offfset of +/- 1MB
> from PC. This is an obvious bug in the GCC as RISC-V has a
> two-instruction construct to jump to any absolute address (AUIPC+JALR).
> 
> However there is no reason to force inlining as the test code works
> perfectly fine without it.
> 
> GCC has a bug report for a similar case (with conditionals):
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93062
> 
> Fixes: a9fe152363 test/ring: add custom element size functional tests
> 
> Signed-off-by: Stanislaw Kardach <kda@semihalf.com>
Acked-by: Bruce Richardson <bruce.richardson@intel.com>