[ADT] Add llvm::to_float

Summary:
The function matches the interface of llvm::to_integer, but as we are
calling out to a C library function, I let it take a Twine argument, so
we can avoid a string copy at least in some cases.

I add a test and replace a couple of existing uses of strtod with this
function.

Reviewers: zturner

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D34518

llvm-svn: 306096

1 files changed, 4 insertions, 7 deletions

diff --git a/llvm/lib/Support/CommandLine.cpp b/llvm/lib/Support/CommandLine.cpp
index de0ca940b40..0345a5e3d2a 100644
--- a/llvm/lib/Support/CommandLine.cpp
+++ b/llvm/lib/Support/CommandLine.cpp
@@ -24,6 +24,7 @@
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/SmallPtrSet.h"
 #include "llvm/ADT/SmallString.h"
+#include "llvm/ADT/StringExtras.h"
 #include "llvm/ADT/StringMap.h"
 #include "llvm/ADT/Twine.h"
 #include "llvm/Config/config.h"
@@ -1522,13 +1523,9 @@ bool parser<unsigned long long>::parse(Option &O, StringRef ArgName,
 // parser<double>/parser<float> implementation
 //
 static bool parseDouble(Option &O, StringRef Arg, double &Value) {
-  SmallString<32> TmpStr(Arg.begin(), Arg.end());
-  const char *ArgStart = TmpStr.c_str();
-  char *End;
-  Value = strtod(ArgStart, &End);
-  if (*End != 0)
-    return O.error("'" + Arg + "' value invalid for floating point argument!");
-  return false;
+  if (to_float(Arg, Value))
+    return false;
+  return O.error("'" + Arg + "' value invalid for floating point argument!");
 }
 
 bool parser<double>::parse(Option &O, StringRef ArgName, StringRef Arg,