[Matrix] Remove bitcast when casting between matrices of the same size

[SaurabhJha]

Summary

In matrix type casts, we were doing bitcast when the matrices had the same size. This was incorrect and this patch fixes that.
Also added some new CodeGen tests for signed <-> usigned conversions

[fhahn]

LGTM, thanks!

I can commit this change on your behalf in a bit

[SaurabhJha]

In D101754#2733273, @fhahn wrote:

LGTM, thanks!

I can commit this change on your behalf in a bit

Cheers Florian!

clang/lib/CodeGen/CGExprScalar.cpp

Value *ScalarExprEmitter::EmitScalarCast(Value *Src, QualType SrcType,
                                          llvm::Type *DstTy,
                                          ScalarConversionOpts Opts) {
   // The Element types determine the type of cast to perform.
   llvm::Type *SrcElementTy;
   llvm::Type *DstElementTy;
   QualType SrcElementType;
   QualType DstElementType;
   if (SrcType->isMatrixType() && DstType->isMatrixType()) {
-    // Allow bitcast between matrixes of the same size.
-    if (SrcTy->getPrimitiveSizeInBits() == DstTy->getPrimitiveSizeInBits())
-      return Builder.CreateBitCast(Src, DstTy, "conv");
-
     SrcElementTy = cast<llvm::VectorType>(SrcTy)->getElementType();
     DstElementTy = cast<llvm::VectorType>(DstTy)->getElementType();
     SrcElementType = SrcType->castAs<MatrixType>()->getElementType();
     DstElementType = DstType->castAs<MatrixType>()->getElementType();
   } else {
     assert(!SrcType->isMatrixType() && !DstType->isMatrixType() &&
            "cannot cast between matrix and non-matrix types");
     SrcElementTy = SrcTy;

clang/test/CodeGen/matrix-cast.c

void cast_int_matrix_to_short(ix5x5 i, sx5x5 s) {
   // CHECK-NEXT:  ret void
 
   s = (sx5x5)i;
 }
 
 void cast_int_matrix_to_float(ix5x5 i, fx5x5 f) {
   // CHECK-LABEL: define{{.*}} void @cast_int_matrix_to_float(<25 x i32> %i, <25 x float> %f)
   // CHECK:       [[I:%.*]] = load <25 x i32>, <25 x i32>* {{.*}}, align 4
-  // CHECK-NEXT:  [[CONV:%.*]] = bitcast <25 x i32> [[I]] to <25 x float>
+  // CHECK-NEXT:  [[CONV:%.*]] = sitofp <25 x i32> [[I]] to <25 x float>
   // CHECK-NEXT:  store <25 x float> [[CONV]], <25 x float>* {{.*}}, align 4
   // CHECK-NEXT:  ret void
 
   f = (fx5x5)i;
 }
 
+void cast_unsigned_int_matrix_to_float(unsigned_short_int_5x5 u, fx5x5 f) {
+  // CHECK-LABEL: define{{.*}} void @cast_unsigned_int_matrix_to_float(<25 x i16> %u, <25 x float> %f)
+  // CHECK:       [[U:%.*]] = load <25 x i16>, <25 x i16>* {{.*}}, align 2
+  // CHECK-NEXT:  [[CONV:%.*]] = uitofp <25 x i16> [[U]] to <25 x float>
+  // CHECK-NEXT:  store <25 x float> [[CONV]], <25 x float>* {{.*}}, align 4
+  // CHECK-NEXT:  ret void
+
+  f = (fx5x5)u;
+}
+
 void cast_double_matrix_to_int(dx5x5 d, ix5x5 i) {
   // CHECK-LABEL: define{{.*}} void @cast_double_matrix_to_int(<25 x double> %d, <25 x i32> %i)
   // CHECK:       [[D:%.*]] = load <25 x double>, <25 x double>* {{.*}}, align 8
   // CHECK-NEXT:  [[CONV:%.*]] = fptosi <25 x double> [[D]] to <25 x i32>
   // CHECK-NEXT:  store <25 x i32> [[CONV]], <25 x i32>* {{.*}}, align 4
   // CHECK-NEXT:  ret void
 
   i = (ix5x5)d;
void cast_unsigned_long_int_to_unsigned_short_int(unsigned_long_int_5x5 l, unsigned_short_int_5x5 s) {
   // CHECK-LABEL: define{{.*}} void @cast_unsigned_long_int_to_unsigned_short_int(<25 x i64> %l, <25 x i16> %s)
   // CHECK:       [[L:%.*]] = load <25 x i64>, <25 x i64>* %0, align 8
   // CHECK-NEXT:  [[CONV:%.*]] = trunc <25 x i64> [[L]] to <25 x i16>
   // CHECK-NEXT:  store <25 x i16> [[CONV]], <25 x i16>* {{.*}}, align 2
   // CHECK-NEXT:  ret void
 
   s = (unsigned_short_int_5x5)l;
 }
+
+void cast_unsigned_short_int_to_int(unsigned_short_int_5x5 u, ix5x5 i) {
+  // CHECK-LABEL: define{{.*}} void @cast_unsigned_short_int_to_int(<25 x i16> %u, <25 x i32> %i)
+  // CHECK:       [[U:%.*]] = load <25 x i16>, <25 x i16>* %0, align 2
+  // CHECK-NEXT:  [[CONV:%.*]] = zext <25 x i16> [[U]] to <25 x i32>
+  // CHECK-NEXT:  store <25 x i32> [[CONV]], <25 x i32>* {{.*}}, align 4
+  // CHECK-NEXT:  ret void
+
+  i = (ix5x5)u;
+}
+
+void cast_int_to_unsigned_long_int(ix5x5 i, unsigned_long_int_5x5 u) {
+  // CHECK-LABEL: define{{.*}} void @cast_int_to_unsigned_long_int(<25 x i32> %i, <25 x i64> %u)
+  // CHECK:       [[I:%.*]] = load <25 x i32>, <25 x i32>* %0, align 4
+  // CHECK-NEXT:  [[CONV:%.*]] = sext <25 x i32> [[I]] to <25 x i64>
+  // CHECK-NEXT:  store <25 x i64> [[CONV]], <25 x i64>* {{.*}}, align 8
+  // CHECK-NEXT:  ret void
+
+  u = (unsigned_long_int_5x5)i;
+}