[Driver] Use StringRef::consume_front (NFC)

Author: kazutakahirata

clang/lib/Driver/Driver.cpp

@@ -6482,18 +6482,15 @@ bool Driver::GetReleaseVersion(StringRef Str, unsigned &Major, unsigned &Minor,
     return false;
   if (Str.empty())
     return true;
-  if (Str[0] != '.')
+  if (!Str.consume_front("."))
     return false;
 
-  Str = Str.drop_front(1);
-
   if (Str.consumeInteger(10, Minor))
     return false;
   if (Str.empty())
     return true;
-  if (Str[0] != '.')
+  if (!Str.consume_front("."))
     return false;
-  Str = Str.drop_front(1);
 
   if (Str.consumeInteger(10, Micro))
     return false;
@@ -6521,9 +6518,8 @@ bool Driver::GetReleaseVersion(StringRef Str,
     Digits[CurDigit] = Digit;
     if (Str.empty())
       return true;
-    if (Str[0] != '.')
+    if (!Str.consume_front("."))
       return false;
-    Str = Str.drop_front(1);
     CurDigit++;
   }
 

clang/lib/Driver/ToolChains/CommonArgs.cpp

@@ -317,9 +317,7 @@ void tools::handleTargetFeaturesGroup(const Driver &D,
       continue;
     }
 
-    bool IsNegative = Name.starts_with("no-");
-    if (IsNegative)
-      Name = Name.substr(3);
+    bool IsNegative = Name.consume_front("no-");
 
     Features.push_back(Args.MakeArgString((IsNegative ? "-" : "+") + Name));
   }

clang/lib/Driver/ToolChains/Hexagon.cpp

@@ -801,7 +801,6 @@ StringRef HexagonToolChain::GetTargetCPUVersion(const ArgList &Args) {
     CpuArg = A;
 
   StringRef CPU = CpuArg ? CpuArg->getValue() : GetDefaultCPU();
-  if (CPU.starts_with("hexagon"))
-    return CPU.substr(sizeof("hexagon") - 1);
+  CPU.consume_front("hexagon");
   return CPU;
 }