On Wed, 19 Feb 2020, Kees Cook <keescook@xxxxxxxxxxxx> wrote: > 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 > > Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx> Reviewed-by: Jani Nikula <jani.nikula@xxxxxxxxx> If you look at i915/Makefile, you'll see that we don't shy away from enabling lots of extra warnings, and we run our CI with -Werror to keep it clean. It does not seem like -Wswitch-unreachable does me any good, though... is it new? BR, Jani. > --- > drivers/gpu/drm/i915/display/intel_display.c | 6 ++++-- > drivers/gpu/drm/i915/intel_pm.c | 4 ++-- > 2 files changed, 6 insertions(+), 4 deletions(-) > > diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c > index 064dd99bbc49..c829cd26f99e 100644 > --- a/drivers/gpu/drm/i915/display/intel_display.c > +++ b/drivers/gpu/drm/i915/display/intel_display.c > @@ -12960,14 +12960,15 @@ static bool check_digital_port_conflicts(struct intel_atomic_state *state) > WARN_ON(!connector_state->crtc); > > switch (encoder->type) { > - unsigned int port_mask; > case INTEL_OUTPUT_DDI: > if (WARN_ON(!HAS_DDI(to_i915(dev)))) > break; > /* else, fall through */ > case INTEL_OUTPUT_DP: > case INTEL_OUTPUT_HDMI: > - case INTEL_OUTPUT_EDP: > + case INTEL_OUTPUT_EDP: { > + unsigned int port_mask; > + > port_mask = 1 << encoder->port; > > /* the same port mustn't appear more than once */ > @@ -12976,6 +12977,7 @@ static bool check_digital_port_conflicts(struct intel_atomic_state *state) > > used_ports |= port_mask; > break; > + } > case INTEL_OUTPUT_DP_MST: > used_mst_ports |= > 1 << encoder->port; > diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c > index bd2d30ecc030..17d8833787c4 100644 > --- a/drivers/gpu/drm/i915/intel_pm.c > +++ b/drivers/gpu/drm/i915/intel_pm.c > @@ -469,9 +469,9 @@ static void vlv_get_fifo_size(struct intel_crtc_state *crtc_state) > struct vlv_fifo_state *fifo_state = &crtc_state->wm.vlv.fifo_state; > enum pipe pipe = crtc->pipe; > int sprite0_start, sprite1_start; > + u32 dsparb, dsparb2, dsparb3; > > switch (pipe) { > - u32 dsparb, dsparb2, dsparb3; > case PIPE_A: > dsparb = I915_READ(DSPARB); > dsparb2 = I915_READ(DSPARB2); > @@ -1969,6 +1969,7 @@ static void vlv_atomic_update_fifo(struct intel_atomic_state *state, > const struct vlv_fifo_state *fifo_state = > &crtc_state->wm.vlv.fifo_state; > int sprite0_start, sprite1_start, fifo_size; > + u32 dsparb, dsparb2, dsparb3; > > if (!crtc_state->fifo_changed) > return; > @@ -1994,7 +1995,6 @@ static void vlv_atomic_update_fifo(struct intel_atomic_state *state, > spin_lock(&uncore->lock); > > switch (crtc->pipe) { > - u32 dsparb, dsparb2, dsparb3; > case PIPE_A: > dsparb = intel_uncore_read_fw(uncore, DSPARB); > dsparb2 = intel_uncore_read_fw(uncore, DSPARB2); > -- Jani Nikula, Intel Open Source Graphics Center _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
