From 54519ed70fbe154e196d04a8b62f6ea6aeded52a Mon Sep 17 00:00:00 2001
From: Tim Foley <tfoley@nvidia.com>
Date: Fri, 7 Jul 2017 08:16:09 -0700
Subject: Fix alignment computation for `std140` uniforms

Fixes #55

I was incorrectly computing alignment as `elementSize * elementAlignment`, rounded up to a power of two (which works out to be `elementSize` squared), when I should have been using `elementSize * elementCount`, rounded up to a power of two.
---
 source/slang/type-layout.cpp         |  5 ++--
 tests/reflection/gh-55.glsl          | 13 +++++++++++
 tests/reflection/gh-55.glsl.expected | 45 ++++++++++++++++++++++++++++++++++++
 3 files changed, 61 insertions(+), 2 deletions(-)
 create mode 100644 tests/reflection/gh-55.glsl
 create mode 100644 tests/reflection/gh-55.glsl.expected

diff --git a/source/slang/type-layout.cpp b/source/slang/type-layout.cpp
index 2fcf64226..fbaec3736 100644
--- a/source/slang/type-layout.cpp
+++ b/source/slang/type-layout.cpp
@@ -163,10 +163,11 @@ struct Std140LayoutRulesImpl : GLSLConstantBufferLayoutRulesImpl
     SimpleLayoutInfo GetVectorLayout(SimpleLayoutInfo elementInfo, size_t elementCount) override
     {
         assert(elementInfo.kind == LayoutResourceKind::Uniform);
+        auto size = elementInfo.size * elementCount;
         SimpleLayoutInfo vectorInfo(
             LayoutResourceKind::Uniform,
-            elementInfo.size * elementCount,
-            RoundUpToPowerOfTwo(elementInfo.size * elementInfo.alignment));
+            size,
+            RoundUpToPowerOfTwo(size));
         return vectorInfo;
     }
 };
diff --git a/tests/reflection/gh-55.glsl b/tests/reflection/gh-55.glsl
new file mode 100644
index 000000000..4ced68c9e
--- /dev/null
+++ b/tests/reflection/gh-55.glsl
@@ -0,0 +1,13 @@
+//TEST(smoke):SIMPLE:-profile ps_4_0 -target reflection-json
+
+// Confirm fix for GitHub issue #55
+
+layout(set = 0, binding = 0)
+uniform PerFrameCB
+{
+	vec2 offset;
+	vec2 scale;
+};
+
+void main()
+{}
diff --git a/tests/reflection/gh-55.glsl.expected b/tests/reflection/gh-55.glsl.expected
new file mode 100644
index 000000000..8cdebdcd8
--- /dev/null
+++ b/tests/reflection/gh-55.glsl.expected
@@ -0,0 +1,45 @@
+result code = 0
+standard error = {
+}
+standard output = {
+{
+    "parameters": [
+        {
+            "name": "PerFrameCB",
+            "binding": {"kind": "descriptorTableSlot", "index": 0},
+            "type": {
+                "kind": "constantBuffer",
+                "elementType": {
+                    "kind": "struct",
+                    "fields": [
+                        {
+                            "name": "offset",
+                            "type": {
+                                "kind": "vector",
+                                "elementCount": 2,
+                                "elementType": {
+                                    "kind": "scalar",
+                                    "scalarType": "float32"
+                                }
+                            },
+                            "binding": {"kind": "uniform", "offset": 0, "size": 8}
+                        },
+                        {
+                            "name": "scale",
+                            "type": {
+                                "kind": "vector",
+                                "elementCount": 2,
+                                "elementType": {
+                                    "kind": "scalar",
+                                    "scalarType": "float32"
+                                }
+                            },
+                            "binding": {"kind": "uniform", "offset": 8, "size": 8}
+                        }
+                    ]
+                }
+            }
+        }
+    ]
+}
+}
-- 
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