From c576a09d5796b12b8e2ecad066df42648946f169 Mon Sep 17 00:00:00 2001
From: Henri Verbeet <hverbeet@locutus.nl>
Date: Wed, 22 Oct 2025 00:40:33 +0200
Subject: [PATCH] vkd3d-shader/msl: Implement VSIR_OP_FIRSTBIT_LO.

---
 libs/vkd3d-shader/msl.c        | 24 ++++++++++++++++++++++++
 tests/hlsl/bitwise.shader_test |  2 +-
 2 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/libs/vkd3d-shader/msl.c b/libs/vkd3d-shader/msl.c
index 25a10145a..6e15e1744 100644
--- a/libs/vkd3d-shader/msl.c
+++ b/libs/vkd3d-shader/msl.c
@@ -698,6 +698,27 @@ static void msl_dot(struct msl_generator *gen, const struct vkd3d_shader_instruc
     msl_dst_cleanup(&dst, &gen->string_buffers);
 }
 
+static void msl_firstbit(struct msl_generator *gen, const struct vkd3d_shader_instruction *ins)
+{
+    unsigned int mask_size;
+    struct msl_src src;
+    struct msl_dst dst;
+    uint32_t mask;
+
+    mask = msl_dst_init(&dst, gen, ins, &ins->dst[0]);
+    msl_src_init(&src, gen, &ins->src[0], mask);
+
+    if ((mask_size = vsir_write_mask_component_count(mask)) > 1)
+        msl_print_assignment(gen, &dst, "select(uint%u(0xffffffffu), ctz(%s), bool%u(%s))",
+                mask_size, src.str->buffer, mask_size, src.str->buffer);
+    else
+        msl_print_assignment(gen, &dst, "%s ? ctz(%s) : 0xffffffffu",
+                src.str->buffer, src.str->buffer);
+
+    msl_src_cleanup(&src, &gen->string_buffers);
+    msl_dst_cleanup(&dst, &gen->string_buffers);
+}
+
 static void msl_intrinsic(struct msl_generator *gen, const struct vkd3d_shader_instruction *ins, const char *op)
 {
     struct vkd3d_string_buffer *args;
@@ -1499,6 +1520,9 @@ static void msl_handle_instruction(struct msl_generator *gen, const struct vkd3d
         case VSIR_OP_EXP:
             msl_intrinsic(gen, ins, "exp2");
             break;
+        case VSIR_OP_FIRSTBIT_LO:
+            msl_firstbit(gen, ins);
+            break;
         case VSIR_OP_FRC:
             msl_intrinsic(gen, ins, "fract");
             break;
diff --git a/tests/hlsl/bitwise.shader_test b/tests/hlsl/bitwise.shader_test
index 82a8d4630..4e46c9e72 100644
--- a/tests/hlsl/bitwise.shader_test
+++ b/tests/hlsl/bitwise.shader_test
@@ -264,7 +264,7 @@ uint4 main() : sv_target
 
 [test]
 uniform 0 uint4 0 0xffffffff 0x00001000 0x00760400
-todo(msl & sm>=6) draw quad
+draw quad
 probe (0, 0) u32(0xffffffff, 0, 12, 10)
 
 [pixel shader]