Add some comments for TableGen's NeonEmitter.
llvm-svn: 120596
diff --git a/llvm/utils/TableGen/NeonEmitter.cpp b/llvm/utils/TableGen/NeonEmitter.cpp
index aa6daaf..5de289e 100644
--- a/llvm/utils/TableGen/NeonEmitter.cpp
+++ b/llvm/utils/TableGen/NeonEmitter.cpp
@@ -293,9 +293,9 @@
bool pntr = false;
if (mod == 'v')
- return "v";
+ return "v"; // void
if (mod == 'i')
- return "i";
+ return "i"; // int
// base type to get the type string for.
char type = ClassifyType(typestr, quad, poly, usgn);
@@ -303,11 +303,13 @@
// Based on the modifying character, change the type and width if necessary.
type = ModType(mod, type, quad, poly, usgn, scal, cnst, pntr);
+ // All pointers are void* pointers. Change type to 'v' now.
if (pntr) {
usgn = false;
poly = false;
type = 'v';
}
+ // Treat half-float ('h') types as unsigned short ('s') types.
if (type == 'h') {
type = 's';
usgn = true;
@@ -320,7 +322,7 @@
if (usgn)
s.push_back('U');
- if (type == 'l')
+ if (type == 'l') // 64-bit long
s += "LLi";
else
s.push_back(type);
@@ -338,7 +340,7 @@
// fashion, storing them to a pointer arg.
if (ret) {
if (mod >= '2' && mod <= '4')
- return "vv*";
+ return "vv*"; // void result with void* first argument
if (mod == 'f' || (ck != ClassB && type == 'f'))
return quad ? "V4f" : "V2f";
if (ck != ClassB && type == 's')
@@ -711,9 +713,9 @@
// the immediate passed by the user.
bool define = proto.find('i') != std::string::npos;
- // If all types are the same size, bitcasting the args will take care
- // of arg checking. The actual signedness etc. will be taken care of with
- // special enums.
+ // Check if the prototype has a scalar operand with the type of the vector
+ // elements. If not, bitcasting the args will take care of arg checking.
+ // The actual signedness etc. will be taken care of with special enums.
if (proto.find('s') == std::string::npos)
ck = ClassB;
@@ -736,6 +738,7 @@
s += "__builtin_neon_";
if (splat) {
+ // Call the non-splat builtin: chop off the "_n" suffix from the name.
std::string vname(name, 0, name.size()-2);
s += MangleName(vname, typestr, ck);
} else {
@@ -750,6 +753,8 @@
for (unsigned i = 1, e = proto.size(); i != e; ++i, ++arg) {
std::string args = std::string(&arg, 1);
+
+ // Wrap macro arguments in parenthesis.
if (define)
args = "(" + args + ")";