[PATCH v6 0/1] MR308: vkd3d-shader/hlsl: Initialize unused constant values in compilation passes.

[Francisco Casas (＠fcasas)]

Even though the uninitialized values shouldn't be used in the output
binary program, they still show up in it, and affect the checksum, so
we better make them zeroes.

This error was reported by valgrind:

```
libtool --mode=execute valgrind --track-origins=yes vkd3d-build/tests/shader_runner vkd3d/tests/hlsl/static-initializer.shader_test
```

```
==46180== Conditional jump or move depends on uninitialised value(s)
==46180==    at 0x48D98C7: parse_dxbc.isra.0 (dxbc.c:182)
==46180==    by 0x48DA044: vkd3d_shader_parse_dxbc (dxbc.c:308)
==46180==    by 0x488D1B6: vkd3d_shader_parse_dxbc_source_type (vkd3d_shader_utils.h:37)
==46180==    by 0x488D1B6: create_shader_stage.isra.0 (state.c:1988)
==46180==    by 0x48926B6: d3d12_pipeline_state_init_graphics (state.c:3084)
==46180==    by 0x4893A96: d3d12_pipeline_state_create_graphics (state.c:3280)
==46180==    by 0x4878498: d3d12_device_CreateGraphicsPipelineState (device.c:2619)
==46180==    by 0x1FFEFFECC7: ???
==46180==    by 0xE8: ???
==46180==    by 0x47: ???
==46180==    by 0x61: ???
==46180==    by 0x660066000000023: ???
==46180==    by 0x661066100000044: ???
==46180==  Uninitialised value was created by a stack allocation
==46180==    at 0x48F3FF0: hlsl_fold_constant_swizzles (hlsl_constant_ops.c:1010)
```

Thank you valgrind! :smile:

--
  v6: vkd3d-shader/tpf: Avoid reading constant value components beyond type's width (Valgrind).

https://gitlab.winehq.org/wine/vkd3d/-/merge_requests/308

[PATCH v6 1/1] vkd3d-shader/tpf: Avoid reading constant value components beyond type's width (Valgrind).

[Francisco Casas]

From: Francisco Casas

We are passing map writemasks that may have more components than the
constant's data type, so a (j < width) check is added to avoid reading
components from the constant that are not intended to be used.

Remaining values in the register are initialized to zero.
---
 libs/vkd3d-shader/tpf.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/libs/vkd3d-shader/tpf.c b/libs/vkd3d-shader/tpf.c
index 550f9b27..cf2cc0d1 100644
--- a/libs/vkd3d-shader/tpf.c
+++ b/libs/vkd3d-shader/tpf.c
@@ -3715,8 +3715,10 @@ static void sm4_src_from_constant_value(struct sm4_src_register *src,
         src->reg.dim = VKD3D_SM4_DIMENSION_VEC4;
         for (i = 0; i < 4; ++i)
         {
-            if (map_writemask & (1u << i))
+            if ((map_writemask & (1u << i)) && (j < width))
                 src->reg.immconst_uint[i] = value->u[j++].u;
+            else
+                src->reg.immconst_uint[i] = 0;
         }
     }
 }

[Zebediah Figura (＠zfigura)]

> > Actually, for that matter, shouldn't "j < width" be an assertion?
>
> No, because we are deliberately passing map_writemask with more than "width" bites on in some places, usually using `VKD3DSP_WRITEMASK_ALL`.

Fair enough. [To be pedantic, we don't do that for sm4_src_from_constant_value(), but the precedent is set by sm4_src_from_node().]

[PATCH v6 0/1] MR308: vkd3d-shader/hlsl: Initialize unused constant values in compilation passes. - approved

[Zebediah Figura (＠zfigura)]

This merge request was approved by Zebediah Figura.

[PATCH v6 0/1] MR308: vkd3d-shader/hlsl: Initialize unused constant values in compilation passes. - approved

[Henri Verbeet (＠hverbeet)]

This merge request was approved by Henri Verbeet.