Make tests properly exercise Some("") global names. (gfx-rs#1503)

The GLSL empty-global-name.frag test doesn't suffice because the GLSL front end
doesn't produce the same IR as the SPIR-V included in the bug report. As far as
I know, only a genuine SPIR-V input test can produce a global whose name is
`Some("")`.

Include the SPIR-V assembly source.

tests/in/spv/empty-global-name.spvasm

@@ -0,0 +1,44 @@
+;; Make sure we handle globals whose assigned name is "".
+;;
+;; In MSL, the anonymous global sometimes ends up looking like
+;;
+;;     struct Blah { int member; } ;
+;;
+;; where the null name just becomes an empty string before that last semicolon.
+;; This is, unfortunately, valid MSL, simply declaring the type Blah, so it will
+;; pass validation. However, an attempt to *use* the global will generate a
+;; garbage expression like ".member", so we include a function that returns the
+;; member's value.
+
+                        OpCapability Shader
+                        OpMemoryModel Logical GLSL450
+                        OpEntryPoint GLCompute %main "main" %global
+                        OpExecutionMode %main LocalSize 64 1 1
+
+                        OpName %global ""
+                        OpDecorate %block Block
+                        OpMemberDecorate %block 0 Offset 0
+                        OpDecorate %global DescriptorSet 0
+                        OpDecorate %global Binding 0
+
+                %void = OpTypeVoid
+                 %int = OpTypeInt 32 1
+               %block = OpTypeStruct %int
+             %ptr_int = OpTypePointer StorageBuffer %int
+           %ptr_block = OpTypePointer StorageBuffer %block
+             %fn_void = OpTypeFunction %void
+              %fn_int = OpTypeFunction %int
+                %zero = OpConstant %int 0
+                 %one = OpConstant %int 1
+
+;; This global is said to have a name of "".
+              %global = OpVariable %ptr_block StorageBuffer
+
+                %main = OpFunction %void None %fn_void
+        %main_prelude = OpLabel
+          %member_ptr = OpAccessChain %ptr_int %global %zero
+          %member_val = OpLoad %int %member_ptr
+            %plus_one = OpIAdd %int %member_val %one
+                        OpStore %member_ptr %plus_one
+                        OpReturn
+                        OpFunctionEnd

tests/out/hlsl/empty-global-name.hlsl

@@ -0,0 +1,19 @@
+
+struct type1 {
+    int member;
+};
+
+RWByteAddressBuffer global : register(u0);
+
+void function()
+{
+    int _expr8 = asint(global.Load(0));
+    global.Store(0, asuint((_expr8 + 1)));
+    return;
+}
+
+[numthreads(64, 1, 1)]
+void main()
+{
+    function();
+}

tests/out/hlsl/empty-global-name.hlsl.config

@@ -0,0 +1,3 @@
+vertex=()
+fragment=()
+compute=(main:cs_5_1 )

tests/out/msl/empty-global-name.msl

@@ -0,0 +1,21 @@
+// language: metal1.1
+#include <metal_stdlib>
+#include <simd/simd.h>
+
+struct type1 {
+    int member;
+};
+
+void function(
+    device type1& global
+) {
+    int _e8 = global.member;
+    global.member = _e8 + 1;
+    return;
+}
+
+kernel void main1(
+  device type1& global [[user(fake0)]]
+) {
+    function(global);
+}

tests/out/wgsl/empty-global-name.wgsl

@@ -0,0 +1,18 @@
+[[block]]
+struct type2 {
+    member: i32;
+};
+
+[[group(0), binding(0)]]
+var<storage, read_write> global: type2;
+
+fn function1() {
+    let e8: i32 = global.member;
+    global.member = (e8 + 1);
+    return;
+}
+
+[[stage(compute), workgroup_size(64, 1, 1)]]
+fn main() {
+    function1();
+}

tests/snapshots.rs

@@ -598,6 +598,16 @@ fn convert_spv_inverse_hyperbolic_trig_functions() {
     );
 }
 
+#[cfg(feature = "spv-in")]
+#[test]
+fn convert_spv_empty_global_name() {
+    convert_spv(
+        "empty-global-name",
+        true,
+        Targets::HLSL | Targets::WGSL | Targets::METAL,
+    );
+}
+
 #[cfg(feature = "glsl-in")]
 #[allow(unused_variables)]
 #[test]