From 66d994566c68c2da66fba783389e5fa87c54d737 Mon Sep 17 00:00:00 2001
From: Dzmitry Malyshau <kvarkus@gmail.com>
Date: Tue, 8 Dec 2020 17:25:16 -0500
Subject: [PATCH] [spv] force treating the built-in scalar types as unsigned

---
 src/front/spv/mod.rs        |  31 ++++++++++++++++++++++++++++++-
 test-data/spv/quad.vert.spv | Bin 0 -> 884 bytes
 tests/convert.rs            |  21 ++++++++++++++++++++-
 3 files changed, 50 insertions(+), 2 deletions(-)
 create mode 100644 test-data/spv/quad.vert.spv

diff --git a/src/front/spv/mod.rs b/src/front/spv/mod.rs
index f13c3c7577..ad7c208519 100644
--- a/src/front/spv/mod.rs
+++ b/src/front/spv/mod.rs
@@ -2367,11 +2367,40 @@ impl<I: Iterator<Item = u32>> Parser<I> {
             crate::StorageAccess::empty()
         };
 
+        let ty = match binding {
+            // SPIR-V only cares about some of the built-in types being integer.
+            // Naga requires them to be strictly unsigned, so we have to patch it.
+            Some(crate::Binding::BuiltIn(built_in)) => {
+                let scalar_kind = module.types[lookup_type.handle].inner.scalar_kind();
+                let needs_uint = match built_in {
+                    crate::BuiltIn::BaseInstance
+                    | crate::BuiltIn::BaseVertex
+                    | crate::BuiltIn::InstanceIndex
+                    | crate::BuiltIn::SampleIndex
+                    | crate::BuiltIn::VertexIndex => true,
+                    _ => false,
+                };
+                if needs_uint && scalar_kind == Some(crate::ScalarKind::Sint) {
+                    log::warn!("Treating {:?} as unsigned", built_in);
+                    module.types.fetch_or_append(crate::Type {
+                        name: None,
+                        inner: crate::TypeInner::Scalar {
+                            kind: crate::ScalarKind::Uint,
+                            width: 4,
+                        },
+                    })
+                } else {
+                    lookup_type.handle
+                }
+            }
+            _ => lookup_type.handle,
+        };
+
         let var = crate::GlobalVariable {
             name: dec.name,
             class,
             binding,
-            ty: lookup_type.handle,
+            ty,
             init,
             interpolation: dec.interpolation,
             storage_access,
diff --git a/test-data/spv/quad.vert.spv b/test-data/spv/quad.vert.spv
new file mode 100644
index 0000000000000000000000000000000000000000..ea22e0c6c8c517586dffef3e917584826c32602b
GIT binary patch
literal 884
zcmZ9JO-lk{6os$asAXwpYM(Y{Z3?7CMGzIOEO0Rqw2i<agwjwKE`$1IZTd@Xg3dGV
z3`JLt@4e@K-^rv~IkS}IEN{E!q-<$1W(CVeZ>M|PZI36t_TkY15k<>Hfy9)QiOdMk
z5B&l9ys#l;^h@jgP@t!XzcHSeS@~Xu<Nl;SjPgA7Blq#?{w^F%!s+#(7f#8|+M45o
zaO7Mv#X25cIYCm&Q(yWc9d)H<LD&<nRE=5)9MVxd9J5yR&)bZqcU(<+R-7-?RgaCa
ziSuRW^}>Ow?74{Ns?JXzbof*Gv6%^OKaOAgXD`X7K7M-D1hdx*`maiZ<DQLpb~t8P
z*UQ&oA9`WCZ}Hn}Qyh}i-g0J?-;z!~^^SEbW}puO|0TxLOKtY%8?yJAZ1!6a*lj4A
z8H+KO_)D?>Q&osB3vlfJ9&?qL=LSigW$EyNV%(iwZTN(%OXp7DEsk4}UKQ}2YXjzm
zV;<@>1h^Z;Gp{eeAqm%%4wn)FWpSHr!58pxKYCuO2KU<$xH)&GCpPils&FFw0HeY$
Aw*UYD

literal 0
HcmV?d00001

diff --git a/tests/convert.rs b/tests/convert.rs
index 2946613750..593f9b433e 100644
--- a/tests/convert.rs
+++ b/tests/convert.rs
@@ -173,7 +173,7 @@ fn convert_boids() {
 
 #[cfg(feature = "spv-in")]
 #[test]
-fn convert_cube() {
+fn convert_cube_spv() {
     let mut validator = naga::proc::Validator::new();
     let vs = load_spv("cube.vert.spv");
     validator.validate(&vs).unwrap();
@@ -232,6 +232,25 @@ fn convert_cube() {
     }
 }
 
+#[cfg(feature = "spv-in")]
+#[test]
+fn convert_quad_spv() {
+    let mut validator = naga::proc::Validator::new();
+    // check that integer `gl_VertexIndex` is treated as unsigned
+    let vs = load_spv("quad.vert.spv");
+    validator.validate(&vs).unwrap();
+    #[cfg(feature = "msl-out")]
+    {
+        use naga::back::msl;
+        let options = msl::Options {
+            lang_version: (1, 0),
+            spirv_cross_compatibility: false,
+            binding_map: msl::BindingMap::default(),
+        };
+        msl::write_string(&vs, &options).unwrap();
+    }
+}
+
 #[cfg(feature = "glsl-in")]
 #[test]
 #[ignore]