Add GLSL translations for bit manipulation intrinsics (#430)

The following translations are added:

* HLSL `countbits` becomes GLSL `bitCount`
* HLSL `firstbitlow` becomes GLSL `findLSB`
* HLSL `firstbithight` becomes GLSL `findMSB`
* HLSL `rerverseBits` becomes GLSL `bitfieldReverse`

There are currently no HLSL equivalents for the bitfield insert/extract operations in GLSL. In the future we could expose those as intrinsics under their GLSL names, with HLSL translations, if desired.

2 files changed, 32 insertions, 0 deletions

diff --git a/source/slang/hlsl.meta.slang b/source/slang/hlsl.meta.slang
index 5f3f0aa67..03b48e805 100644
--- a/source/slang/hlsl.meta.slang
+++ b/source/slang/hlsl.meta.slang
@@ -356,6 +356,7 @@ __generic<T : __BuiltinFloatingPointType, let N : int> vector<T,N> cosh(vector<T
 __generic<T : __BuiltinFloatingPointType, let N : int, let M : int> matrix<T,N,M> cosh(matrix<T,N,M> x);
 
 // Population count
+__target_intrinsic(glsl, "bitCount")
 uint countbits(uint value);
 
 // Cross product
@@ -515,17 +516,29 @@ __generic<let N : int> vector<uint,N> f32tof16(vector<float,N> value);
 __generic<T : __BuiltinFloatingPointType, let N : int> vector<T,N> faceforward(vector<T,N> n, vector<T,N> i, vector<T,N> ng);
 
 // Find first set bit starting at high bit and working down
+__target_intrinsic(glsl,"findMSB")
 int firstbithigh(int value);
+
+__target_intrinsic(glsl,"findMSB")
 __generic<let N : int> vector<int,N> firstbithigh(vector<int,N> value);
 
+__target_intrinsic(glsl,"findMSB")
 uint firstbithigh(uint value);
+
+__target_intrinsic(glsl,"findMSB")
 __generic<let N : int> vector<uint,N> firstbithigh(vector<uint,N> value);
 
 // Find first set bit starting at low bit and working up
+__target_intrinsic(glsl,"findLSB")
 int firstbitlow(int value);
+
+__target_intrinsic(glsl,"findLSB")
 __generic<let N : int> vector<int,N> firstbitlow(vector<int,N> value);
 
+__target_intrinsic(glsl,"findLSB")
 uint firstbitlow(uint value);
+
+__target_intrinsic(glsl,"findLSB")
 __generic<let N : int> vector<uint,N> firstbitlow(vector<uint,N> value);
 
 // Floor (HLSL SM 1.0)
@@ -815,7 +828,10 @@ __generic<T : __BuiltinFloatingPointType, let N : int>
 vector<T,N> refract(vector<T,N> i, vector<T,N> n, float eta);
 
 // Reverse order of bits
+__target_intrinsic(glsl, "bitfieldReverse")
 uint reversebits(uint value);
+
+__target_intrinsic(glsl, "bitfieldReverse")
 __generic<let N : int> vector<uint,N> reversebits(vector<uint,N> value);
 
 // Round-to-nearest
diff --git a/source/slang/hlsl.meta.slang.h b/source/slang/hlsl.meta.slang.h
index eae31a75a..6351f2c8b 100644
--- a/source/slang/hlsl.meta.slang.h
+++ b/source/slang/hlsl.meta.slang.h
@@ -359,6 +359,7 @@ sb << "__generic<T : __BuiltinFloatingPointType, let N : int> vector<T,N> cosh(v
 sb << "__generic<T : __BuiltinFloatingPointType, let N : int, let M : int> matrix<T,N,M> cosh(matrix<T,N,M> x);\n";
 sb << "\n";
 sb << "// Population count\n";
+sb << "__target_intrinsic(glsl, \"bitCount\")\n";
 sb << "uint countbits(uint value);\n";
 sb << "\n";
 sb << "// Cross product\n";
@@ -518,17 +519,29 @@ sb << "// Flip surface normal to face forward, if needed\n";
 sb << "__generic<T : __BuiltinFloatingPointType, let N : int> vector<T,N> faceforward(vector<T,N> n, vector<T,N> i, vector<T,N> ng);\n";
 sb << "\n";
 sb << "// Find first set bit starting at high bit and working down\n";
+sb << "__target_intrinsic(glsl,\"findMSB\")\n";
 sb << "int firstbithigh(int value);\n";
+sb << "\n";
+sb << "__target_intrinsic(glsl,\"findMSB\")\n";
 sb << "__generic<let N : int> vector<int,N> firstbithigh(vector<int,N> value);\n";
 sb << "\n";
+sb << "__target_intrinsic(glsl,\"findMSB\")\n";
 sb << "uint firstbithigh(uint value);\n";
+sb << "\n";
+sb << "__target_intrinsic(glsl,\"findMSB\")\n";
 sb << "__generic<let N : int> vector<uint,N> firstbithigh(vector<uint,N> value);\n";
 sb << "\n";
 sb << "// Find first set bit starting at low bit and working up\n";
+sb << "__target_intrinsic(glsl,\"findLSB\")\n";
 sb << "int firstbitlow(int value);\n";
+sb << "\n";
+sb << "__target_intrinsic(glsl,\"findLSB\")\n";
 sb << "__generic<let N : int> vector<int,N> firstbitlow(vector<int,N> value);\n";
 sb << "\n";
+sb << "__target_intrinsic(glsl,\"findLSB\")\n";
 sb << "uint firstbitlow(uint value);\n";
+sb << "\n";
+sb << "__target_intrinsic(glsl,\"findLSB\")\n";
 sb << "__generic<let N : int> vector<uint,N> firstbitlow(vector<uint,N> value);\n";
 sb << "\n";
 sb << "// Floor (HLSL SM 1.0)\n";
@@ -818,7 +831,10 @@ sb << "__generic<T : __BuiltinFloatingPointType, let N : int>\n";
 sb << "vector<T,N> refract(vector<T,N> i, vector<T,N> n, float eta);\n";
 sb << "\n";
 sb << "// Reverse order of bits\n";
+sb << "__target_intrinsic(glsl, \"bitfieldReverse\")\n";
 sb << "uint reversebits(uint value);\n";
+sb << "\n";
+sb << "__target_intrinsic(glsl, \"bitfieldReverse\")\n";
 sb << "__generic<let N : int> vector<uint,N> reversebits(vector<uint,N> value);\n";
 sb << "\n";
 sb << "// Round-to-nearest\n";