Add support for pointers to the language.

Pointers can be either uniform or varying, and behave correspondingly.
e.g.: "uniform float * varying" is a varying pointer to uniform float
data in memory, and "float * uniform" is a uniform pointer to varying
data in memory.  Like other types, pointers are varying by default.

Pointer-based expressions, & and *, sizeof, ->, pointer arithmetic,
and the array/pointer duality all bahave as in C.  Array arguments
to functions are converted to pointers, also like C.

There is a built-in NULL for a null pointer value; conversion from
compile-time constant 0 values to NULL still needs to be implemented.

Other changes:
- Syntax for references has been updated to be C++ style; a useful
  warning is now issued if the "reference" keyword is used.
- It is now illegal to pass a varying lvalue as a reference parameter
  to a function; references are essentially uniform pointers.
  This case had previously been handled via special case call by value
  return code.  That path has been removed, now that varying pointers
  are available to handle this use case (and much more).
- Some stdlib routines have been updated to take pointers as
  arguments where appropriate (e.g. prefetch and the atomics).
  A number of others still need attention.
- All of the examples have been updated
- Many new tests

TODO: documentation

examples/volume_rendering/Makefile

@@ -8,7 +8,7 @@ TASK_OBJ=$(addprefix objs/, $(subst ../,, $(TASK_CXX:.cpp=.o)))
 CXX=g++
 CXXFLAGS=-Iobjs/ -O3 -Wall -m64
 ISPC=ispc
-ISPCFLAGS=-O2 --target=sse2,sse4-x2 --arch=x86-64
+ISPCFLAGS=-O2 --target=sse2,sse4-x2 --arch=x86-64 --opt=32-bit-addressing
 
 OBJS=objs/volume.o objs/volume_serial.o $(TASK_OBJ) objs/volume_ispc.o \
 	objs/volume_ispc_sse2.o objs/volume_ispc_sse4.o

examples/volume_rendering/volume.ispc

@@ -41,7 +41,7 @@ struct Ray {
 static void
 generateRay(const uniform float raster2camera[4][4], 
             const uniform float camera2world[4][4],
-            float x, float y, reference Ray ray) {
+            float x, float y, Ray &ray) {
     // transform raster coordinate (x, y, 0) to camera space
     float camx = raster2camera[0][0] * x + raster2camera[0][1] * y + raster2camera[0][3];
     float camy = raster2camera[1][0] * x + raster2camera[1][1] * y + raster2camera[1][3];
@@ -70,7 +70,7 @@ Inside(float3 p, float3 pMin, float3 pMax) {
 
 
 static bool
-IntersectP(Ray ray, float3 pMin, float3 pMax, reference float hit0, reference float hit1) {
+IntersectP(Ray ray, float3 pMin, float3 pMax, float &hit0, float &hit1) {
     float t0 = -1e30, t1 = 1e30;
 
     float3 tNear = (pMin - ray.origin) / ray.dir;
@@ -141,7 +141,7 @@ static inline float3 Offset(float3 p, float3 pMin, float3 pMax) {
 
 static inline float Density(float3 Pobj, float3 pMin, float3 pMax, 
                             uniform float density[], uniform int nVoxels[3],
-                            reference uniform bool checkForSameVoxel) {
+                            uniform bool &checkForSameVoxel) {
     if (!Inside(Pobj, pMin, pMax)) 
         return 0;
     // Compute voxel coordinates and offsets for _Pobj_
@@ -155,8 +155,8 @@ static inline float Density(float3 Pobj, float3 pMin, float3 pMax,
     // Trilinearly interpolate density values to compute local density
     float d00, d10, d01, d11;
     uniform int uvx, uvy, uvz;
-    if (checkForSameVoxel && reduce_equal(vx, uvx) && reduce_equal(vy, uvy) &&
-        reduce_equal(vz, uvz)) {
+    if (checkForSameVoxel && reduce_equal(vx, &uvx) && reduce_equal(vy, &uvy) &&
+        reduce_equal(vz, &uvz)) {
         // If all of the program instances are inside the same voxel, then
         // we'll call the 'uniform' variant of the voxel density lookup
         // function, thus doing a single load for each value rather than a

examples/volume_rendering/volume.vcxproj

@@ -1,4 +1,4 @@
-<?xml version="1.0" encoding="utf-8"?>
+<?xml version="1.0" encoding="utf-8"?>
 <Project DefaultTargets="Build" ToolsVersion="4.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
   <ItemGroup Label="ProjectConfigurations">
     <ProjectConfiguration Include="Debug|Win32">
@@ -158,13 +158,13 @@
       <FileType>Document</FileType>
       <Command Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'">ispc -O2 %(Filename).ispc -o $(TargetDir)%(Filename).obj -h $(TargetDir)%(Filename)_ispc.h --arch=x86 --target=sse2,sse4-x2
 </Command>
-      <Command Condition="'$(Configuration)|$(Platform)'=='Debug|x64'">ispc -O2 %(Filename).ispc -o $(TargetDir)%(Filename).obj -h $(TargetDir)%(Filename)_ispc.h --target=sse2,sse4-x2
+      <Command Condition="'$(Configuration)|$(Platform)'=='Debug|x64'">ispc -O2 %(Filename).ispc -o $(TargetDir)%(Filename).obj -h $(TargetDir)%(Filename)_ispc.h --target=sse2,sse4-x2 --opt=32-bit-addressing
 </Command>
       <Outputs Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'">$(TargetDir)%(Filename).obj;$(TargetDir)%(Filename)_sse2.obj;$(TargetDir)%(Filename)_sse4.obj;$(TargetDir)%(Filename)_ispc.h</Outputs>
       <Outputs Condition="'$(Configuration)|$(Platform)'=='Debug|x64'">$(TargetDir)%(Filename).obj;$(TargetDir)%(Filename)_sse2.obj;$(TargetDir)%(Filename)_sse4.obj;$(TargetDir)%(Filename)_ispc.h</Outputs>
       <Command Condition="'$(Configuration)|$(Platform)'=='Release|Win32'">ispc -O2 %(Filename).ispc -o $(TargetDir)%(Filename).obj -h $(TargetDir)%(Filename)_ispc.h --arch=x86 --target=sse2,sse4-x2
 </Command>
-      <Command Condition="'$(Configuration)|$(Platform)'=='Release|x64'">ispc -O2 %(Filename).ispc -o $(TargetDir)%(Filename).obj -h $(TargetDir)%(Filename)_ispc.h --target=sse2,sse4-x2
+      <Command Condition="'$(Configuration)|$(Platform)'=='Release|x64'">ispc -O2 %(Filename).ispc -o $(TargetDir)%(Filename).obj -h $(TargetDir)%(Filename)_ispc.h --target=sse2,sse4-x2 --opt=32-bit-addressing
 </Command>
       <Outputs Condition="'$(Configuration)|$(Platform)'=='Release|Win32'">$(TargetDir)%(Filename).obj;$(TargetDir)%(Filename)_sse2.obj;$(TargetDir)%(Filename)_sse4.obj;$(TargetDir)%(Filename)_ispc.h</Outputs>
       <Outputs Condition="'$(Configuration)|$(Platform)'=='Release|x64'">$(TargetDir)%(Filename).obj;$(TargetDir)%(Filename)_sse2.obj;$(TargetDir)%(Filename)_sse4.obj;$(TargetDir)%(Filename)_ispc.h</Outputs>