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drm/amd/display: mark static functions noinline_for_stack
When compiling allmodconfig (CONFIG_WERROR=y) with clang-19, see the following errors: .../display/dc/dml2/display_mode_core.c:6268:13: warning: stack frame size (3128) exceeds limit (3072) in 'dml_prefetch_check' [-Wframe-larger-than] .../display/dc/dml2/dml21/src/dml2_core/dml2_core_dcn4_calcs.c:7236:13: warning: stack frame size (3256) exceeds limit (3072) in 'dml_core_mode_support' [-Wframe-larger-than] Mark static functions called by dml_prefetch_check() and dml_core_mode_support() noinline_for_stack to avoid them become huge functions and thus exceed the frame size limit. A way to reproduce: $ git checkout next-20250107 $ mkdir build_dir $ export PATH=/tmp/llvm-19.1.6-x86_64/bin:$PATH $ make LLVM=1 O=build_dir allmodconfig $ make LLVM=1 O=build_dir drivers/gpu/drm/ -j The way how it chose static functions to mark: [0] Unset CONFIG_WERROR in build_dir/.config. To get display_mode_core.o without errors. [1] Get a function list called by dml_prefetch_check(). $ sed -n '6268,6711p' drivers/gpu/drm/amd/display/dc/dml2/display_mode_core.c \ | sed -n -r 's/.*\W(\w+)\(.*/\1/p' | sort -u >/tmp/syms [2] Get the non-inline function list. Objdump won't show the symbols if they are inline functions. $ make LLVM=1 O=build_dir drivers/gpu/drm/ -j $ objdump -d build_dir/.../display_mode_core.o | \ ./scripts/checkstack.pl x86_64 0 | \ grep -f /tmp/syms | cut -d' ' -f2- >/tmp/orig [3] Get the full function list. Append "-fno-inline" to `CFLAGS_.../display_mode_core.o` in drivers/gpu/drm/amd/display/dc/dml2/Makefile. $ make LLVM=1 O=build_dir drivers/gpu/drm/ -j $ objdump -d build_dir/.../display_mode_core.o | \ ./scripts/checkstack.pl x86_64 0 | \ grep -f /tmp/syms | cut -d' ' -f2- >/tmp/noinline [4] Get the inline function list. If a symbol only in /tmp/noinline but not in /tmp/orig, it is a good candidate to mark noinline. $ diff /tmp/orig /tmp/noinline Chosen functions and their stack sizes: CalculateBandwidthAvailableForImmediateFlip [display_mode_core.o]:144 CalculateExtraLatency [display_mode_core.o]:176 CalculateTWait [display_mode_core.o]:64 CalculateVActiveBandwithSupport [display_mode_core.o]:112 set_calculate_prefetch_schedule_params [display_mode_core.o]:48 CheckGlobalPrefetchAdmissibility [dml2_core_dcn4_calcs.o]:544 calculate_bandwidth_available [dml2_core_dcn4_calcs.o]:320 calculate_vactive_det_fill_latency [dml2_core_dcn4_calcs.o]:272 CalculateDCFCLKDeepSleep [dml2_core_dcn4_calcs.o]:208 CalculateODMMode [dml2_core_dcn4_calcs.o]:208 CalculateOutputLink [dml2_core_dcn4_calcs.o]:176 Signed-off-by: Tzung-Bi Shih <tzungbi@kernel.org> Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
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