From 7dfa9e8f819bb160e0cc0f14b565536a120f46a2 Mon Sep 17 00:00:00 2001
From: Henri Verbeet <hverbeet@locutus.nl>
Date: Fri, 23 May 2025 16:53:38 +0200
Subject: [PATCH] vkd3d-shader/msl: Implement VKD3DSIH_DISCARD.

---
 libs/vkd3d-shader/msl.c        | 30 +++++++++++++++++++++++++-----
 tests/hlsl/clip.shader_test    | 12 ++++++------
 tests/hlsl/discard.shader_test |  4 ++--
 3 files changed, 33 insertions(+), 13 deletions(-)

diff --git a/libs/vkd3d-shader/msl.c b/libs/vkd3d-shader/msl.c
index 948107886..47ea6ce1f 100644
--- a/libs/vkd3d-shader/msl.c
+++ b/libs/vkd3d-shader/msl.c
@@ -737,19 +737,36 @@ static void msl_begin_block(struct msl_generator *gen)
     ++gen->indent;
 }
 
-static void msl_if(struct msl_generator *gen, const struct vkd3d_shader_instruction *ins)
+static void msl_print_condition(struct vkd3d_string_buffer *buffer, struct msl_generator *gen,
+        enum vkd3d_shader_conditional_op op, const struct vkd3d_shader_src_param *arg)
 {
     const char *condition;
     struct msl_src src;
 
-    msl_src_init(&src, gen, &ins->src[0], VKD3DSP_WRITEMASK_0);
+    msl_src_init(&src, gen, arg, VKD3DSP_WRITEMASK_0);
 
-    msl_print_indent(gen->buffer, gen->indent);
-    condition = ins->flags == VKD3D_SHADER_CONDITIONAL_OP_NZ ? "bool" : "!bool";
-    vkd3d_string_buffer_printf(gen->buffer, "if (%s(%s))\n", condition, src.str->buffer);
+    condition = op == VKD3D_SHADER_CONDITIONAL_OP_NZ ? "bool" : "!bool";
+    vkd3d_string_buffer_printf(buffer, "if (%s(%s))\n", condition, src.str->buffer);
 
     msl_src_cleanup(&src, &gen->string_buffers);
+}
 
+static void msl_discard(struct msl_generator *gen, const struct vkd3d_shader_instruction *ins)
+{
+    /* Note that discard_fragment() in Metal 2.2 and earlier behaves like
+     * SPIR-V OpKill, while in Metal 2.3 and later it behaves like
+     * OpDemoteToHelperInvocationEXT. We assume we have at least Metal 3
+     * here. */
+    msl_print_indent(gen->buffer, gen->indent);
+    msl_print_condition(gen->buffer, gen, ins->flags, &ins->src[0]);
+    msl_print_indent(gen->buffer, gen->indent + 1);
+    vkd3d_string_buffer_printf(gen->buffer, "discard_fragment();\n");
+}
+
+static void msl_if(struct msl_generator *gen, const struct vkd3d_shader_instruction *ins)
+{
+    msl_print_indent(gen->buffer, gen->indent);
+    msl_print_condition(gen->buffer, gen, ins->flags, &ins->src[0]);
     msl_begin_block(gen);
 }
 
@@ -1024,6 +1041,9 @@ static void msl_handle_instruction(struct msl_generator *gen, const struct vkd3d
         case VKD3DSIH_DEFAULT:
             msl_default(gen);
             break;
+        case VKD3DSIH_DISCARD:
+            msl_discard(gen, ins);
+            break;
         case VKD3DSIH_DIV:
             msl_binop(gen, ins, "/");
             break;
diff --git a/tests/hlsl/clip.shader_test b/tests/hlsl/clip.shader_test
index f253fbcb8..bb7597cfd 100644
--- a/tests/hlsl/clip.shader_test
+++ b/tests/hlsl/clip.shader_test
@@ -9,20 +9,20 @@ float4 main() : sv_target
 
 [test]
 uniform 0 float4 1 2 3 4
-todo(glsl | msl) draw quad
+todo(glsl) draw quad
 probe (0, 0) rgba (1, 2, 3, 4)
 uniform 0 float4 9 8 7 6
-todo(glsl | msl) draw quad
+todo(glsl) draw quad
 probe (0, 0) rgba (9, 8, 7, 6)
 uniform 0 float4 -1 8 7 6
-todo(glsl | msl) draw quad
+todo(glsl) draw quad
 probe (0, 0) rgba (9, 8, 7, 6)
 uniform 0 float4 9 0 7 6
-todo(glsl | msl) draw quad
+todo(glsl) draw quad
 probe (0, 0) rgba (9, 0, 7, 6)
 uniform 0 float4 3 -8 3 0
-todo(glsl | msl) draw quad
+todo(glsl) draw quad
 probe (0, 0) rgba (9, 0, 7, 6)
 uniform 0 float4 3 3 3 -1
-todo(glsl | msl) draw quad
+todo(glsl) draw quad
 probe (0, 0) rgba (9, 0, 7, 6)
diff --git a/tests/hlsl/discard.shader_test b/tests/hlsl/discard.shader_test
index a62f74148..ae55fc42a 100644
--- a/tests/hlsl/discard.shader_test
+++ b/tests/hlsl/discard.shader_test
@@ -10,10 +10,10 @@ float4 main() : sv_target
 
 [test]
 uniform 0 float4 1 2 3 4
-todo(sm<4 | glsl | msl) draw quad
+todo(sm<4 | glsl) draw quad
 probe (0, 0) rgba (1, 2, 3, 4)
 uniform 0 float4 9 8 7 6
-todo(sm<4 | glsl | msl) draw quad
+todo(sm<4 | glsl) draw quad
 probe (0, 0) rgba (1, 2, 3, 4)
 
 [require]