From 38345d590949b0c88d83bccb259364f02a59a90e Mon Sep 17 00:00:00 2001
From: Ali Cheraghi <alichraghi@proton.me>
Date: Thu, 31 Oct 2024 01:42:30 +0330
Subject: [PATCH] std.gpu: add `instanceIndex`

---
 lib/std/gpu.zig | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/lib/std/gpu.zig b/lib/std/gpu.zig
index f3b37eff94..3f33ffee0e 100644
--- a/lib/std/gpu.zig
+++ b/lib/std/gpu.zig
@@ -47,6 +47,17 @@ pub fn vertexIndex(comptime ptr: *addrspace(.input) u32) void {
     );
 }
 
+/// Will make `ptr` contain the index of the instance that is
+/// being processed by the current vertex shader invocation.
+/// `ptr` must be a reference to variable or struct field.
+pub fn instanceIndex(comptime ptr: *addrspace(.input) u32) void {
+    asm volatile (
+        \\OpDecorate %ptr BuiltIn InstanceIndex
+        :
+        : [ptr] "" (ptr),
+    );
+}
+
 /// Output fragment depth from a `Fragment` entrypoint
 /// `ptr` must be a reference to variable or struct field.
 pub fn fragmentCoord(comptime ptr: *addrspace(.input) @Vector(4, f32)) void {