ADT: Add a string APSInt constructor.

This commit moves the APSInt initialization code that's used by
the LLLexer class into a new APSInt constructor that constructs
APSInts from strings.

This change is useful for MIR Serialization, as it would allow
the MILexer class to use the same APSInt initialization as 
LLexer when parsing immediate machine operands.

llvm-svn: 240436

2 files changed, 20 insertions, 14 deletions

diff --git a/llvm/lib/AsmParser/LLLexer.cpp b/llvm/lib/AsmParser/LLLexer.cpp
index 0bdc3506a30..88f359d4fd5 100644
--- a/llvm/lib/AsmParser/LLLexer.cpp
+++ b/llvm/lib/AsmParser/LLLexer.cpp
@@ -903,20 +903,7 @@ lltok::Kind LLLexer::LexDigitOrNegative() {
   if (CurPtr[0] != '.') {
     if (TokStart[0] == '0' && TokStart[1] == 'x')
       return Lex0x();
-    unsigned Len = CurPtr-TokStart;
-    uint32_t numBits = ((Len * 64) / 19) + 2;
-    APInt Tmp(numBits, StringRef(TokStart, Len), 10);
-    if (TokStart[0] == '-') {
-      uint32_t minBits = Tmp.getMinSignedBits();
-      if (minBits > 0 && minBits < numBits)
-        Tmp = Tmp.trunc(minBits);
-      APSIntVal = APSInt(Tmp, false);
-    } else {
-      uint32_t activeBits = Tmp.getActiveBits();
-      if (activeBits > 0 && activeBits < numBits)
-        Tmp = Tmp.trunc(activeBits);
-      APSIntVal = APSInt(Tmp, true);
-    }
+    APSIntVal = APSInt(StringRef(TokStart, CurPtr - TokStart));
     return lltok::APSInt;
   }
 
diff --git a/llvm/lib/Support/APSInt.cpp b/llvm/lib/Support/APSInt.cpp
index 73acafa690c..975457c070a 100644
--- a/llvm/lib/Support/APSInt.cpp
+++ b/llvm/lib/Support/APSInt.cpp
@@ -17,6 +17,25 @@
 
 using namespace llvm;
 
+APSInt::APSInt(StringRef Str) {
+  assert(!Str.empty() && "Invalid string length");
+
+  // (Over-)estimate the required number of bits.
+  unsigned NumBits = ((Str.size() * 64) / 19) + 2;
+  APInt Tmp(NumBits, Str, /*Radix=*/10);
+  if (Str[0] == '-') {
+    unsigned MinBits = Tmp.getMinSignedBits();
+    if (MinBits > 0 && MinBits < NumBits)
+      Tmp = Tmp.trunc(MinBits);
+    *this = APSInt(Tmp, /*IsUnsigned=*/false);
+    return;
+  }
+  unsigned ActiveBits = Tmp.getActiveBits();
+  if (ActiveBits > 0 && ActiveBits < NumBits)
+    Tmp = Tmp.trunc(ActiveBits);
+  *this = APSInt(Tmp, /*IsUnsigned=*/true);
+}
+
 void APSInt::Profile(FoldingSetNodeID& ID) const {
   ID.AddInteger((unsigned) (IsUnsigned ? 1 : 0));
   APInt::Profile(ID);