-Wframe-larger-than in drivers/gpu/drm/amd/amdgpu/../display/dc/dml/dcn31{,4}/display_mode_vba_31{,4}.c

[nathanchance]

After LLVM commit 8ac9461e48e0 ("[SLP] Reject 2-element vectorization when vector inst count exceeds scalar", 2026-04-11), I am seeing two new -Wframe-larger-than instances from drivers/gpu/drm/amd/display (the directory that keeps on giving...)

$ echo CONFIG_DRM_AMDGPU=y >kernel/configs/repro.config

$ kmake ARCH=x86_64 LLVM=1 mrproper {def,repro.}config drivers/gpu/drm/amd/amdgpu/
drivers/gpu/drm/amd/amdgpu/../display/dc/dml/dcn314/display_mode_vba_314.c:3892:6: error: stack frame size (2104) exceeds limit (2048) in 'dml314_ModeSupportAndSystemConfigurationFull' [-Werror,-Wframe-larger-than]
 3892 | void dml314_ModeSupportAndSystemConfigurationFull(struct display_mode_lib *mode_lib)
      |      ^
1 error generated.
...
drivers/gpu/drm/amd/amdgpu/../display/dc/dml/dcn31/display_mode_vba_31.c:3799:6: error: stack frame size (2104) exceeds limit (2048) in 'dml31_ModeSupportAndSystemConfigurationFull' [-Werror,-Wframe-larger-than]
 3799 | void dml31_ModeSupportAndSystemConfigurationFull(struct display_mode_lib *mode_lib)
      |      ^
1 error generated.
...

At the parent of that LLVM change (a26c1d16bc4328c745c012ae44d43d64ed53b20b), the stack usage is 200 bytes lower or so. We were fairly close to the 2048 bytes limit but this is still somewhat significant.

diff --git a/drivers/gpu/drm/amd/display/dc/dml/Makefile b/drivers/gpu/drm/amd/display/dc/dml/Makefile
index 268b5fbdb48b..9eba549c45dc 100644
--- a/drivers/gpu/drm/amd/display/dc/dml/Makefile
+++ b/drivers/gpu/drm/amd/display/dc/dml/Makefile
@@ -56,9 +56,9 @@ CFLAGS_$(AMDDALPATH)/dc/dml/dcn21/display_mode_vba_21.o := $(dml_ccflags) $(fram
 CFLAGS_$(AMDDALPATH)/dc/dml/dcn21/display_rq_dlg_calc_21.o := $(dml_ccflags)
 CFLAGS_$(AMDDALPATH)/dc/dml/dcn30/display_mode_vba_30.o := $(dml_ccflags) $(frame_warn_flag)
 CFLAGS_$(AMDDALPATH)/dc/dml/dcn30/display_rq_dlg_calc_30.o := $(dml_ccflags)
-CFLAGS_$(AMDDALPATH)/dc/dml/dcn31/display_mode_vba_31.o := $(dml_ccflags) $(frame_warn_flag)
+CFLAGS_$(AMDDALPATH)/dc/dml/dcn31/display_mode_vba_31.o := $(dml_ccflags) -Wframe-larger-than=1500
 CFLAGS_$(AMDDALPATH)/dc/dml/dcn31/display_rq_dlg_calc_31.o := $(dml_ccflags)
-CFLAGS_$(AMDDALPATH)/dc/dml/dcn314/display_mode_vba_314.o := $(dml_ccflags) $(frame_warn_flag)
+CFLAGS_$(AMDDALPATH)/dc/dml/dcn314/display_mode_vba_314.o := $(dml_ccflags) -Wframe-larger-than=1500
 CFLAGS_$(AMDDALPATH)/dc/dml/dcn314/display_rq_dlg_calc_314.o := $(dml_ccflags)
 CFLAGS_$(AMDDALPATH)/dc/dml/dcn314/dcn314_fpu.o := $(dml_ccflags)
 CFLAGS_$(AMDDALPATH)/dc/dml/dcn30/dcn30_fpu.o := $(dml_ccflags)

drivers/gpu/drm/amd/amdgpu/../display/dc/dml/dcn31/display_mode_vba_31.c:3799:6: error: stack frame size (1880) exceeds limit (1500) in 'dml31_ModeSupportAndSystemConfigurationFull' [-Werror,-Wframe-larger-than]
 3799 | void dml31_ModeSupportAndSystemConfigurationFull(struct display_mode_lib *mode_lib)
      |      ^
drivers/gpu/drm/amd/amdgpu/../display/dc/dml/dcn314/display_mode_vba_314.c:3892:6: error: stack frame size (1848) exceeds limit (1500) in 'dml314_ModeSupportAndSystemConfigurationFull' [-Werror,-Wframe-larger-than]
 3892 | void dml314_ModeSupportAndSystemConfigurationFull(struct display_mode_lib *mode_lib)
      |      ^

I am guessing this heuristic messes with something else in the pipeline.