Fix broken -emit-spirv-via-glsl test option (#7091)

Fixes issue #6898

The -emit-spirv-via-glsl slang-test option has been broken for
some amount of time. Tests that were using it were operating as
if using -emit-spirv-directly, leading to many duplicated tests.

After fixing the test option, there were an number of errors that
appeared as a result.

This change fixes the broken test option and the resulting test
errors. Some of the test errors revealed some legitimate issues,
such as:

-The GLSL bitCount instrinsic only supports 32-bit integers and
 requires emulation for other bit widths.
-Emitting GLSL 8-bit and 16-bit glsl integer types did not emit
 the proper extension requirements
-Emitting GLSL and casting for 16-bit integers was missing a
 closing parenthesis.
-Missing profile for GL_EXT_shader_explicit_arithmetic_types
-Missing toType cases for UInt8/Int8 for the kIROp_BitCast case
 in tryEmitInstExprImpl.

1 files changed, 23 insertions, 4 deletions

diff --git a/source/slang/hlsl.meta.slang b/source/slang/hlsl.meta.slang
index d7a65c031..6fb3af7fd 100644
--- a/source/slang/hlsl.meta.slang
+++ b/source/slang/hlsl.meta.slang
@@ -8084,9 +8084,20 @@ uint countbits(T value)
         // 16-bit support dependent on SM6.2 and dxil
         __intrinsic_asm "countbits";
     case glsl:
-        // 64-bit support dependent on GL_ARB_gpu_shader_int64
-        // 16-bit support dependent on GL_EXT_shader_16bit_storage
-        __intrinsic_asm "bitCount";
+        if(T is int64_t || T  is uint64_t)
+        {
+            return __emulatedCountbits64(__intCast<uint64_t>(value));
+        }
+        else if (T is int16_t || T  is uint16_t)
+        {
+            // emulate 16-bit
+            return countbits(__intCast<uint32_t>(value));
+        }
+        else
+        {
+            // bitCount only supports 32-bit
+            __intrinsic_asm "bitCount";
+        }
     case metal:
         if (T is int64_t || T  is uint64_t)
         {
@@ -8150,7 +8161,15 @@ vector<uint, N> countbits(vector<T, N> value)
     case hlsl:
         __intrinsic_asm "countbits";
     case glsl:
-        __intrinsic_asm "bitCount";
+        if(T is int64_t || T  is uint64_t || T is int16_t || T  is uint16_t)
+        {
+            // Emulate 64-bit and 16-bit
+            VECTOR_MAP_UNARY(uint, N, countbits, value);
+        }
+        else
+        {
+            __intrinsic_asm "bitCount";
+        }
     case metal:
         if(T is int64_t || T  is uint64_t || T is int16_t || T  is uint16_t)
         {