[PATCH v2] automation/eclair: deviate R2.6 for the x86 emulator

[Shuaidong Chen <shuaidong.chen@xxxxxxx>]

MISRA C:2012 Rule 2.6 (advisory) states that "a function should not
contain unused label declarations".

With CONFIG_HVM=n, private.h defines X86EMUL_NO_FPU, X86EMUL_NO_MMX and
X86EMUL_NO_SIMD.  The CASE_SIMD_* macros then expand to plain labels
instead of case labels, and the gotos to several hand-written simd_*
labels are preprocessed out, leaving 91 unused labels in
x86_emulate.c.  The build already acknowledges this by passing
-Wno-unused-label for that object.

Annotating these labels would only add churn to the emulator.  As done
for Rule 16.2, deviate the rule for the emulator as a whole.

Signed-off-by: Shuaidong Chen <shuaidong.chen@xxxxxxx>
---
v2:
- Drop the __maybe_unused annotations (v1 patch 1) and the CASE_SIMD_*
  specific deviation (v1 patch 2) in favour of an emulator-wide
  deviation, following the existing one for Rule 16.2.

 automation/eclair_analysis/ECLAIR/deviations.ecl | 5 +++++
 docs/misra/deviations.rst                        | 8 ++++++++
 2 files changed, 13 insertions(+)

diff --git a/automation/eclair_analysis/ECLAIR/deviations.ecl 
b/automation/eclair_analysis/ECLAIR/deviations.ecl
index 296340bb4c..4679e8b250 100644
--- a/automation/eclair_analysis/ECLAIR/deviations.ecl
+++ b/automation/eclair_analysis/ECLAIR/deviations.ecl
@@ -55,6 +55,11 @@ removed by the compiler, the resulting slowdown is 
negligible."
 -config=MC3A2.R2.6,reports+={deliberate, 
"any_area(text(^.*__maybe_unused.*$))"}
 -doc_end
 
+-doc_begin="With CONFIG_HVM=n the FPU, MMX and SIMD parts of the x86 emulator 
are compiled out, leaving labels with no goto targeting them, many generated by 
the CASE_SIMD_* macros.
+Annotating them would only add churn to the emulator, therefore it is deemed 
better to leave such files as is."
+-config=MC3A2.R2.6,reports+={deliberate, 
"any_area(any_loc(file(^xen/arch/x86/x86_emulate/.*$)))"}
+-doc_end
+
 #
 # Series 3.
 #
diff --git a/docs/misra/deviations.rst b/docs/misra/deviations.rst
index bee4686675..7e70b2b79f 100644
--- a/docs/misra/deviations.rst
+++ b/docs/misra/deviations.rst
@@ -116,6 +116,14 @@ Deviations related to MISRA C:2012 Rules:
        such labels poses no risks.
      - Tagged as `deliberate` for ECLAIR.
 
+   * - R2.6
+     - With CONFIG_HVM=n the FPU, MMX and SIMD parts of the x86 emulator are
+       compiled out, leaving labels with no goto targeting them, many of them
+       generated by the CASE_SIMD_* macros. Annotating them would only add
+       churn to the emulator, therefore it is deemed better to leave such
+       files as is.
+     - Tagged as `deliberate` for ECLAIR.
+
    * - R3.1
      - Comments starting with '/\*' and containing URLs are safe as they are
        not instances of commented-out code.
-- 
2.34.1