drm/i915: Distribute switch variables for initialization
authorKees Cook <keescook@chromium.org>
Fri, 21 Feb 2020 00:05:17 +0000 (16:05 -0800)
committerJani Nikula <jani.nikula@intel.com>
Sun, 23 Feb 2020 15:31:37 +0000 (17:31 +0200)
commit2713eb41a1a9149b330b80e03b2fbfa17c514c3f
treeb3c68ed5862eaeb0d5bd73c61796849f61ffd431
parentf8226d02857b2d950e0f058d6e9c04a3e7df79cf
drm/i915: Distribute switch variables for initialization

Variables declared in a switch statement before any case statements
cannot be automatically initialized with compiler instrumentation (as
they are not part of any execution flow). With GCC's proposed automatic
stack variable initialization feature, this triggers a warning (and they
don't get initialized). Clang's automatic stack variable initialization
(via CONFIG_INIT_STACK_ALL=y) doesn't throw a warning, but it also
doesn't initialize such variables[1]. Note that these warnings (or silent
skipping) happen before the dead-store elimination optimization phase,
so even when the automatic initializations are later elided in favor of
direct initializations, the warnings remain.

To avoid these problems, move such variables into the "case" where
they're used or lift them up into the main function body.

drivers/gpu/drm/i915/display/intel_display.c: In function ‘check_digital_port_conflicts’:
drivers/gpu/drm/i915/display/intel_display.c:12963:17: warning: statement will never be executed [-Wswitch-unreachable]
12963 |    unsigned int port_mask;
      |                 ^~~~~~~~~

drivers/gpu/drm/i915/intel_pm.c: In function ‘vlv_get_fifo_size’:
drivers/gpu/drm/i915/intel_pm.c:474:7: warning: statement will never be executed [-Wswitch-unreachable]
  474 |   u32 dsparb, dsparb2, dsparb3;
      |       ^~~~~~
drivers/gpu/drm/i915/intel_pm.c: In function ‘vlv_atomic_update_fifo’:
drivers/gpu/drm/i915/intel_pm.c:1997:7: warning: statement will never be executed [-Wswitch-unreachable]
 1997 |   u32 dsparb, dsparb2, dsparb3;
      |       ^~~~~~

[1] https://bugs.llvm.org/show_bug.cgi?id=44916

Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/202002201602.92CADF7D@keescook
drivers/gpu/drm/i915/display/intel_display.c
drivers/gpu/drm/i915/intel_pm.c