4 files changed, 43 insertions, 23 deletions
diff --git a/indra/llmath/llv4math.h b/indra/llmath/llv4math.h
index 4a299716b1..f064b39947 100644
--- a/indra/llmath/llv4math.h
+++ b/indra/llmath/llv4math.h
@@ -9,6 +9,25 @@
 #ifndef	LL_LLV4MATH_H
 #define	LL_LLV4MATH_H
 
+// *NOTE: We do not support SSE acceleration on Windows builds.
+// Our minimum specification for the viewer includes 1 GHz Athlon processors,
+// which covers the Athlon Thunderbird series that does not support SSE.
+//
+// Our header files include statements like this
+//   const F32 HAVOK_TIMESTEP = 1.f / 45.f;
+// This creates "globals" that are included in each .obj file.  If a single
+// .cpp file has SSE code generation turned on (eg, llviewerjointmesh_sse.cpp)
+// these globals will be initialized using SSE instructions.  This causes SL
+// to crash before main() on processors without SSE.  Untangling all these 
+// headers/variables is too much work for the small performance gains of 
+// vectorization.
+//
+// Therefore we only support vectorization on builds where the everything is 
+// built with SSE or Altivec.  See https://jira.secondlife.com/browse/VWR-1610
+// and https://jira.lindenlab.com/browse/SL-47720 for details.
+//
+// Sorry the code is such a mess. JC
+
 //-----------------------------------------------------------------------------
 //-----------------------------------------------------------------------------
 // LLV4MATH - GNUC
@@ -46,6 +65,9 @@ typedef float	V4F32							__attribute__((vector_size(16)));
 //-----------------------------------------------------------------------------
 //-----------------------------------------------------------------------------
 
+// Only vectorize if the entire Windows build uses SSE.
+// _M_IX86_FP is set when SSE code generation is turned on, and I have
+// confirmed this in VS2003, VS2003 SP1, and VS2005. JC
 #if LL_MSVC && _M_IX86_FP
 
 #define			LL_VECTORIZE					1
diff --git a/indra/newview/llviewerjointmesh_sse.cpp b/indra/newview/llviewerjointmesh_sse.cpp
index c4f8ff4fa8..579c5d2687 100644
--- a/indra/newview/llviewerjointmesh_sse.cpp
+++ b/indra/newview/llviewerjointmesh_sse.cpp
@@ -1,6 +1,9 @@
 /** 
- * @file llviewerjointmesh.cpp
- * @brief LLV4 class implementation with LLViewerJointMesh class
+ * @file llviewerjointmesh_sse.cpp
+ * @brief SSE vectorized joint skinning code, only used when video card does
+ * not support avatar vertex programs.
+ *
+ * *NOTE: Disabled on Windows builds. See llv4math.h for details.
  *
  * Copyright (c) 2007-$CurrentYear$, Linden Research, Inc.
  * $License$
@@ -10,9 +13,7 @@
 // Header Files
 //-----------------------------------------------------------------------------
 
-// Do not use precompiled headers, because we need to build this file with
-// SSE support, but not the precompiled header file. JC
-#include "linden_common.h"
+#include "llviewerprecompiledheaders.h"
 
 #include "llviewerjointmesh.h"
 
@@ -27,7 +28,6 @@
 #include "llv4matrix4.h"
 #include "v3math.h"
 
-// *NOTE: SSE must be enabled for this module
 
 #if LL_VECTORIZE
 
@@ -88,7 +88,6 @@ void LLViewerJointMesh::updateGeometrySSE(LLFace *face, LLPolyMesh *mesh)
 void LLViewerJointMesh::updateGeometrySSE(LLFace *face, LLPolyMesh *mesh)
 {
 	LLViewerJointMesh::updateGeometryVectorized(face, mesh);
-	return;
 }
 
 #endif
diff --git a/indra/newview/llviewerjointmesh_sse2.cpp b/indra/newview/llviewerjointmesh_sse2.cpp
index cae602ac14..9ef2b4692a 100644
--- a/indra/newview/llviewerjointmesh_sse2.cpp
+++ b/indra/newview/llviewerjointmesh_sse2.cpp
@@ -1,6 +1,9 @@
 /** 
- * @file llviewerjointmesh.cpp
- * @brief LLV4 class implementation with LLViewerJointMesh class
+ * @file llviewerjointmesh_sse2.cpp
+ * @brief SSE vectorized joint skinning code, only used when video card does
+ * not support avatar vertex programs.
+ *
+ * *NOTE: Disabled on Windows builds. See llv4math.h for details.
  *
  * Copyright (c) 2007-$CurrentYear$, Linden Research, Inc.
  * $License$
@@ -10,9 +13,7 @@
 // Header Files
 //-----------------------------------------------------------------------------
 
-// Do not use precompiled headers, because we need to build this file with
-// SSE support, but not the precompiled header file. JC
-#include "linden_common.h"
+#include "llviewerprecompiledheaders.h"
 
 #include "llviewerjointmesh.h"
 
@@ -29,10 +30,10 @@
 #include "m4math.h"
 #include "v3math.h"
 
-// *NOTE: SSE2 must be enabled for this module
 
 #if LL_VECTORIZE
 
+
 static LLV4Matrix4	sJointMat[32];
 
 inline void matrix_translate(LLV4Matrix4& m, const LLMatrix4* w, const LLVector3& j)
@@ -90,7 +91,6 @@ void LLViewerJointMesh::updateGeometrySSE2(LLFace *face, LLPolyMesh *mesh)
 void LLViewerJointMesh::updateGeometrySSE2(LLFace *face, LLPolyMesh *mesh)
 {
 	LLViewerJointMesh::updateGeometryVectorized(face, mesh);
-	return;
 }
 
 #endif
diff --git a/indra/newview/llviewerjointmesh_vec.cpp b/indra/newview/llviewerjointmesh_vec.cpp
index adc602bdaf..69ddad63fc 100644
--- a/indra/newview/llviewerjointmesh_vec.cpp
+++ b/indra/newview/llviewerjointmesh_vec.cpp
@@ -1,8 +1,11 @@
 /** 
- * @file llviewerjointmesh.cpp
- * @brief LLV4 math class implementation with LLViewerJointMesh class
+ * @file llviewerjointmesh_vec.cpp
+ * @brief Compiler-generated vectorized joint skinning code, works well on
+ * Altivec processors (PowerPC Mac)
  *
- * Copyright (c) 2001-$CurrentYear$, Linden Research, Inc.
+ * *NOTE: See llv4math.h for notes on SSE/Altivec vector code.
+ *
+ * Copyright (c) 2007-$CurrentYear$, Linden Research, Inc.
  * $License$
  */
 
@@ -19,12 +22,8 @@
 #include "llv4matrix3.h"
 #include "llv4matrix4.h"
 
-// *NOTE: This is the fallback code for vectorized joint mesh skinning.
-// For builds that must support non-SSE x86 code (Windows, perhaps Linux)
-// SSE code generation should be disabled for this file.
-//
-// For builds that run on processors that always have SSE (Mac),
-// SSE code generation can be enabled.  JC
+// Generic vectorized code, uses compiler defaults, works well for Altivec
+// on PowerPC.
 
 static LLV4Matrix4	sJointMat[32];