On 12/24/2024 05:46 AM, Nathan Chancellor wrote:
On Sun, Dec 22, 2024 at 12:27:47PM +0800, Tiezhu Yang wrote:
...
With the above changes, there is no "falls through" objtool warning
compiled with both clang 19 and the latest mainline clang 20.
I am somewhat surprised that changes anything because the ASSERT is not
stopping control flow so I would expect the same problem as before. I
guess it does not happen perhaps due to inlining differences? I looked
It is weird and I think it is not the correct way.
at this code briefly when I sent my initial message and I was not sure
where such a check should exist. It does not look like these functions
really do any sort of error handling.
If you are OK with it, I will send a separate formal patch to handle
this issue after doing some more testing.
It may still be worth doing this to get some initial thoughts from the
AMD DRM folks.
I think the correct way is:
Keep the current ASSERT for the aim of debugging, just add BUG() to
stop control flow if the divisor is zero.
--- >8 ---
diff --git a/drivers/gpu/drm/amd/display/dc/basics/fixpt31_32.c
b/drivers/gpu/drm/amd/display/dc/basics/fixpt31_32.c
index 88d3f9d7dd55..e15391e36b40 100644
--- a/drivers/gpu/drm/amd/display/dc/basics/fixpt31_32.c
+++ b/drivers/gpu/drm/amd/display/dc/basics/fixpt31_32.c
@@ -52,6 +52,7 @@ static inline unsigned long long
complete_integer_division_u64(
unsigned long long result;
ASSERT(divisor);
+ BUG_ON(!divisor);
result = div64_u64_rem(dividend, divisor, remainder);
diff --git a/drivers/gpu/drm/amd/display/dc/spl/spl_fixpt31_32.c
b/drivers/gpu/drm/amd/display/dc/spl/spl_fixpt31_32.c
index 131f1e3949d3..ce2036950808 100644
--- a/drivers/gpu/drm/amd/display/dc/spl/spl_fixpt31_32.c
+++ b/drivers/gpu/drm/amd/display/dc/spl/spl_fixpt31_32.c
@@ -30,6 +30,7 @@ static inline unsigned long long
spl_complete_integer_division_u64(
unsigned long long result;
SPL_ASSERT(divisor);
+ BUG_ON(!divisor);
result = spl_div64_u64_rem(dividend, divisor, remainder);
It looks reasonable and works well both on x86 and LoongArch, there are
no the following objtool warnings:
dc_fixpt_recip() falls through to next function dc_fixpt_sinc()
spl_fixpt_recip() falls through to next function spl_fixpt_sinc()
If no more comments, I will send a separate formal patch for your
review in the next week.
Thanks,
Tiezhu
