Fix up translation of `GetDimensions()`

Fixes #122

- In cases with an explicit mip level being specified, there was a mistake in how the argument for setting the mip level in the GLSL code was constructed that led to a parse error in GLSL

- Also, that argument is a `uint` in HLSL and an `int` in GLSL, so an explicit cast was needed

- The GLSL functions here seem to require a newer GLSL (at least higher than `420`), so I had to add in a capability for builtins to specify a required GLSL version. For now I made these ones require `450`.

- Added a test case to confirm that our lowering works (for some definition of "works")

1 files changed, 3 insertions, 1 deletions

diff --git a/source/slang/slang-stdlib.cpp b/source/slang/slang-stdlib.cpp
index a62db693c..7850b0ce0 100644
--- a/source/slang/slang-stdlib.cpp
+++ b/source/slang/slang-stdlib.cpp
@@ -1417,6 +1417,7 @@ namespace Slang
                     for(int includeMipInfo = 0; includeMipInfo < 2; ++includeMipInfo)
                     {
                         {
+                            sb << "__glsl_version(450)\n";
                             sb << "__intrinsic(glsl, \"(";
 
                             int aa = 0;
@@ -1424,8 +1425,9 @@ namespace Slang
                             if (includeMipInfo)
                             {
                                 int mipLevelArg = aa++;
-                                lodStr.append("$");
+                                lodStr = "int($";
                                 lodStr.append(mipLevelArg);
+                                lodStr.append(")");
                             }
 
                             int cc = 0;