[PATCH vkd3d 2/9] vkd3d-shader/spirv: Correctly handle bit shifts greater than 31 bits.
Henri Verbeet
hverbeet at codeweavers.com
Tue Oct 12 11:31:09 CDT 2021
From: Conor McCarthy <cmccarthy at codeweavers.com>
This is undefined behaviour in SPIR-V, but well-defined in Direct3D, so we
should explicitly 'and' the shift amount with 31.
Based on a vkd3d-proton patch by Philip Rebohle.
Signed-off-by: Conor McCarthy <cmccarthy at codeweavers.com>
Signed-off-by: Henri Verbeet <hverbeet at codeweavers.com>
---
v3: Minor modifications to the comment and commit message.
This supersedes patch 216958.
libs/vkd3d-shader/spirv.c | 15 +++++++++++++++
1 file changed, 15 insertions(+)
diff --git a/libs/vkd3d-shader/spirv.c b/libs/vkd3d-shader/spirv.c
index ebaf1631..58bf3d9c 100644
--- a/libs/vkd3d-shader/spirv.c
+++ b/libs/vkd3d-shader/spirv.c
@@ -6840,6 +6840,21 @@ static void vkd3d_dxbc_compiler_emit_alu_instruction(struct vkd3d_dxbc_compiler
for (i = 0; i < instruction->src_count; ++i)
src_ids[i] = vkd3d_dxbc_compiler_emit_load_src(compiler, &src[i], dst->write_mask);
+ /* The SPIR-V specification states, "The resulting value is undefined if
+ * Shift is greater than or equal to the bit width of the components of
+ * Base." Direct3D applies only the lowest 5 bits of the shift.
+ *
+ * Microsoft fxc will compile immediate constants larger than 5 bits.
+ * Fixing up the constants would be more elegant, but the simplest way is
+ * to let this handle constants too. */
+ if (instruction->handler_idx == VKD3DSIH_ISHL || instruction->handler_idx == VKD3DSIH_ISHR
+ || instruction->handler_idx == VKD3DSIH_USHR)
+ {
+ uint32_t mask_id = vkd3d_dxbc_compiler_get_constant_vector(compiler,
+ VKD3D_SHADER_COMPONENT_UINT, vkd3d_write_mask_component_count(dst->write_mask), 0x1f);
+ src_ids[1] = vkd3d_spirv_build_op_and(builder, type_id, src_ids[1], mask_id);
+ }
+
val_id = vkd3d_spirv_build_op_trv(builder, &builder->function_stream, op, type_id,
src_ids, instruction->src_count);
if (instruction->flags & VKD3DSI_PRECISE_XYZW)
--
2.20.1
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