Add StringRef::compare_numeric and use it to sort TableGen register records.

This means that our Registers are now ordered R7, R8, R9, R10, R12, ...
Not R1, R10, R11, R12, R2, R3, ...

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@104745 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 28 insertions, 0 deletions

diff --git a/lib/Support/StringRef.cpp b/lib/Support/StringRef.cpp
index 2b262dc..ca0f518 100644
--- a/lib/Support/StringRef.cpp
+++ b/lib/Support/StringRef.cpp
@@ -23,6 +23,10 @@ static char ascii_tolower(char x) {
   return x;
 }
 
+static bool ascii_isdigit(char x) {
+  return x >= '0' && x <= '9';
+}
+
 /// compare_lower - Compare strings, ignoring case.
 int StringRef::compare_lower(StringRef RHS) const {
   for (size_t I = 0, E = min(Length, RHS.Length); I != E; ++I) {
@@ -37,6 +41,30 @@ int StringRef::compare_lower(StringRef RHS) const {
   return Length < RHS.Length ? -1 : 1;
 }
 
+/// compare_numeric - Compare strings, handle embedded numbers.
+int StringRef::compare_numeric(StringRef RHS) const {
+  for (size_t I = 0, E = min(Length, RHS.Length); I != E; ++I) {
+    if (Data[I] == RHS.Data[I])
+      continue;
+    if (ascii_isdigit(Data[I]) && ascii_isdigit(RHS.Data[I])) {
+      // The longer sequence of numbers is larger. This doesn't really handle
+      // prefixed zeros well.
+      for (size_t J = I+1; J != E+1; ++J) {
+        bool ld = J < Length && ascii_isdigit(Data[J]);
+        bool rd = J < RHS.Length && ascii_isdigit(RHS.Data[J]);
+        if (ld != rd)
+          return rd ? -1 : 1;
+        if (!rd)
+          break;
+      }
+    }
+    return Data[I] < RHS.Data[I] ? -1 : 1;
+  }
+  if (Length == RHS.Length)
+        return 0;
+  return Length < RHS.Length ? -1 : 1;
+}
+
 // Compute the edit distance between the two given strings.
 unsigned StringRef::edit_distance(llvm::StringRef Other, 
                                   bool AllowReplacements) {