[PATCH 0/1] MR723: vkd3d-shader/spirv: Implement MAD in two operations if flagged as precise.

[Conor McCarthy (＠cmccarthy)]

This would eliminate the todo for the precise mad() test in !718. Maybe we need test results on nvidia and intel to decide if we actually want this.

-- 
https://gitlab.winehq.org/wine/vkd3d/-/merge_requests/723

[PATCH 1/1] vkd3d-shader/spirv: Implement MAD in two operations if flagged as precise.

[Conor McCarthy]

From: Conor McCarthy <cmccarthy(a)codeweavers.com>

---
 libs/vkd3d-shader/spirv.c | 34 ++++++++++++++++++++++++++++++++--
 1 file changed, 32 insertions(+), 2 deletions(-)

diff --git a/libs/vkd3d-shader/spirv.c b/libs/vkd3d-shader/spirv.c
index 5403e5443..06408919a 100644
--- a/libs/vkd3d-shader/spirv.c
+++ b/libs/vkd3d-shader/spirv.c
@@ -1447,6 +1447,20 @@ static uint32_t vkd3d_spirv_build_op_isub(struct vkd3d_spirv_builder *builder,
             SpvOpISub, result_type, operand0, operand1);
 }
 
+static uint32_t vkd3d_spirv_build_op_fadd(struct vkd3d_spirv_builder *builder,
+        uint32_t result_type, uint32_t operand0, uint32_t operand1)
+{
+    return vkd3d_spirv_build_op_tr2(builder, &builder->function_stream,
+            SpvOpFAdd, result_type, operand0, operand1);
+}
+
+static uint32_t vkd3d_spirv_build_op_fmul(struct vkd3d_spirv_builder *builder,
+        uint32_t result_type, uint32_t operand0, uint32_t operand1)
+{
+    return vkd3d_spirv_build_op_tr2(builder, &builder->function_stream,
+            SpvOpFMul, result_type, operand0, operand1);
+}
+
 static uint32_t vkd3d_spirv_build_op_fdiv(struct vkd3d_spirv_builder *builder,
         uint32_t result_type, uint32_t operand0, uint32_t operand1)
 {
@@ -7202,8 +7216,24 @@ static void spirv_compiler_emit_ext_glsl_instruction(struct spirv_compiler *comp
     for (i = 0; i < instruction->src_count; ++i)
         src_id[i] = spirv_compiler_emit_load_src(compiler, &src[i], dst->write_mask);
 
-    val_id = vkd3d_spirv_build_op_ext_inst(builder, type_id,
-            instr_set_id, glsl_inst, src_id, instruction->src_count);
+    if (instruction->handler_idx == VKD3DSIH_MAD && (instruction->flags & VKD3DSI_PRECISE_XYZW))
+    {
+        /* The HLSL docs state: "If components of a mad instruction are tagged as precise, the
+         * hardware must execute a mad instruction or the exact equivalent, and it cannot split
+         * it into a multiply followed by an add."
+         * But DXIL.rst states the opposite: "Floating point multiply & add. This operation is
+         * not fused for "precise" operations."
+         * Windows drivers seem to conform with the latter, for SM 4-5 and SM 6. */
+        val_id = vkd3d_spirv_build_op_fmul(builder, type_id, src_id[0], src_id[1]);
+        vkd3d_spirv_build_op_decorate(builder, val_id, SpvDecorationNoContraction, NULL, 0);
+        val_id = vkd3d_spirv_build_op_fadd(builder, type_id, val_id, src_id[2]);
+        vkd3d_spirv_build_op_decorate(builder, val_id, SpvDecorationNoContraction, NULL, 0);
+    }
+    else
+    {
+        val_id = vkd3d_spirv_build_op_ext_inst(builder, type_id,
+                instr_set_id, glsl_inst, src_id, instruction->src_count);
+    }
 
     if (instruction->handler_idx == VKD3DSIH_FIRSTBIT_HI
             || instruction->handler_idx == VKD3DSIH_FIRSTBIT_SHI)
-- 
GitLab

https://gitlab.winehq.org/wine/vkd3d/-/merge_requests/723

[Giovanni Mascellani (＠giomasce)]

That todo succeeds on all the hardware I managed to test with once I cherry pick this on top of !718. I tested:
* RADV,
* Intel,
* NVIDIA proprietary,
* llvmpipe.

So I would accept this after !718 is in and removing the todo.

-- 
https://gitlab.winehq.org/wine/vkd3d/-/merge_requests/723#note_64881

[Conor McCarthy (＠cmccarthy)]

On Fri Mar 15 12:14:27 2024 +0000, Giovanni Mascellani wrote:
> That todo succeeds on all the hardware I managed to test with once I
> cherry pick this on top of !718. I tested:
> * RADV,
> * Intel,
> * NVIDIA proprietary,
> * llvmpipe.
> So I would accept this after !718 is in and removing the todo.
> I was thinking also of Windows, because if implementations vary then a subtle difference in our is not so important.

-- 
https://gitlab.winehq.org/wine/vkd3d/-/merge_requests/723#note_64885