Fix output for matrix multiple in GLSL code (#228)

When Slang sees a matrix multiplication `M * v` in GLSL code it should (obviously) output GLSL code that also does `M * v`, but there was a bug introduced where the type-checker manages to resolve the operation and recognize it as a matrix-vector multiply, and then the code-generation logic says "oh, I'm generating output for GLSL, and that is reversed from HLSL/Slang, so I'd better reverse these operands!" and outputs `v * M`... which isn't what we want.

I've fixed the problem in an expedient way, by having the front-end resolve the operation to what it believes is an intrinsic multiply operation, rather than a matrix-vector operation. If we ever support cross compilation *from* GLSL (unlikely), we've need to fix this up so that we have both real matrix-vector multiplies and "reversed" multiplies where the operands folow the GLSL convention).

I've added two tests here to confirm the fix. The one under `tests/bugs` catches the actual issue described above, and confirms the fix. The other one under `tests/cross-compile` is just to make sure that we *do* properly reverse the operands to a matrix-vector product when converting from Slang to GLSL.

2 files changed, 6 insertions, 6 deletions

diff --git a/source/slang/glsl.meta.slang b/source/slang/glsl.meta.slang
index 5cfb5e7c0..4aa3f059c 100644
--- a/source/slang/glsl.meta.slang
+++ b/source/slang/glsl.meta.slang
@@ -43,13 +43,13 @@ sb << "__generic<T : __BuiltinArithmeticType, let N : int, let M :int> __intrins
 sb << "__generic<T : __BuiltinArithmeticType, let N : int> __intrinsic_op(dot) T operator*(vector<T,N> x, vector<T,N> y);\n";
 
 // vector-matrix
-sb << "__generic<T : __BuiltinArithmeticType, let N : int, let M : int> __intrinsic_op(mulVectorMatrix) vector<T,M> operator*(vector<T,N> x, matrix<T,N,M> y);\n";
+sb << "__generic<T : __BuiltinArithmeticType, let N : int, let M : int> __intrinsic_op(mul) vector<T,M> operator*(vector<T,N> x, matrix<T,N,M> y);\n";
 
 // matrix-vector
-sb << "__generic<T : __BuiltinArithmeticType, let N : int, let M : int> __intrinsic_op(mulMatrixVector) vector<T,N> operator*(matrix<T,N,M> x, vector<T,M> y);\n";
+sb << "__generic<T : __BuiltinArithmeticType, let N : int, let M : int> __intrinsic_op(mul) vector<T,N> operator*(matrix<T,N,M> x, vector<T,M> y);\n";
 
 // matrix-matrix
-sb << "__generic<T : __BuiltinArithmeticType, let R : int, let N : int, let C : int> __intrinsic_op(mulMatrixMatrix) matrix<T,R,C> operator*(matrix<T,R,N> x, matrix<T,N,C> y);\n";
+sb << "__generic<T : __BuiltinArithmeticType, let R : int, let N : int, let C : int> __intrinsic_op(mul) matrix<T,R,C> operator*(matrix<T,R,N> x, matrix<T,N,C> y);\n";
 
 
 
diff --git a/source/slang/glsl.meta.slang.h b/source/slang/glsl.meta.slang.h
index a4aade3c2..a735b3beb 100644
--- a/source/slang/glsl.meta.slang.h
+++ b/source/slang/glsl.meta.slang.h
@@ -44,13 +44,13 @@ sb << "__generic<T : __BuiltinArithmeticType, let N : int, let M :int> __intrins
 sb << "__generic<T : __BuiltinArithmeticType, let N : int> __intrinsic_op(dot) T operator*(vector<T,N> x, vector<T,N> y);\n";
 
 // vector-matrix
-sb << "__generic<T : __BuiltinArithmeticType, let N : int, let M : int> __intrinsic_op(mulVectorMatrix) vector<T,M> operator*(vector<T,N> x, matrix<T,N,M> y);\n";
+sb << "__generic<T : __BuiltinArithmeticType, let N : int, let M : int> __intrinsic_op(mul) vector<T,M> operator*(vector<T,N> x, matrix<T,N,M> y);\n";
 
 // matrix-vector
-sb << "__generic<T : __BuiltinArithmeticType, let N : int, let M : int> __intrinsic_op(mulMatrixVector) vector<T,N> operator*(matrix<T,N,M> x, vector<T,M> y);\n";
+sb << "__generic<T : __BuiltinArithmeticType, let N : int, let M : int> __intrinsic_op(mul) vector<T,N> operator*(matrix<T,N,M> x, vector<T,M> y);\n";
 
 // matrix-matrix
-sb << "__generic<T : __BuiltinArithmeticType, let R : int, let N : int, let C : int> __intrinsic_op(mulMatrixMatrix) matrix<T,R,C> operator*(matrix<T,R,N> x, matrix<T,N,C> y);\n";
+sb << "__generic<T : __BuiltinArithmeticType, let R : int, let N : int, let C : int> __intrinsic_op(mul) matrix<T,R,C> operator*(matrix<T,R,N> x, matrix<T,N,C> y);\n";