Fix bug with APInt::getBitsNeeded with for base 10 numbers 0-9.

llvm-svn: 79593

llvm/lib/Support/APInt.cpp

@@ -44,6 +44,35 @@ inline static uint64_t* getMemory(unsigned numWords) {
   return result;
 }
 
+/// A utility function that converts a character to a digit.
+inline static unsigned getDigit(char cdigit, uint8_t radix) {
+  // Get a digit
+  unsigned digit = 0;
+  if (radix == 16) {
+    if (!isxdigit(cdigit))
+      llvm_unreachable("Invalid hex digit in string");
+    if (isdigit(cdigit))
+      digit = cdigit - '0';
+    else if (cdigit >= 'a')
+      digit = cdigit - 'a' + 10;
+    else if (cdigit >= 'A')
+      digit = cdigit - 'A' + 10;
+    else
+      llvm_unreachable("huh? we shouldn't get here");
+  } else if (isdigit(cdigit)) {
+    digit = cdigit - '0';
+    assert((radix == 10 ||
+            (radix == 8 && digit != 8 && digit != 9) ||
+            (radix == 2 && (digit == 0 || digit == 1))) &&
+           "Invalid digit in string for given radix");
+  } else {
+    llvm_unreachable("Invalid character in digit string");
+  }
+
+  return digit;
+}
+
+
 void APInt::initSlowCase(unsigned numBits, uint64_t val, bool isSigned) {
   pVal = getClearedMemory(getNumWords());
   pVal[0] = val;
@@ -611,22 +640,27 @@ unsigned APInt::getBitsNeeded(const StringRef& str, uint8_t radix) {
   if (radix == 16)
     return slen * 4 + isNegative;
 
-  // Otherwise it must be radix == 10, the hard case
-  assert(radix == 10 && "Invalid radix");
-
   // This is grossly inefficient but accurate. We could probably do something
   // with a computation of roughly slen*64/20 and then adjust by the value of
   // the first few digits. But, I'm not sure how accurate that could be.
 
   // Compute a sufficient number of bits that is always large enough but might
-  // be too large. This avoids the assertion in the constructor.
+  // be too large. This avoids the assertion in the constructor. This
-  unsigned sufficient = slen*64/18;
+  // calculation doesn't work appropriately for the numbers 0-9, so just use 4
+  // bits in that case.
+  unsigned sufficient = slen == 1 ? 4 : slen * 64/18;
 
   // Convert to the actual binary value.
   APInt tmp(sufficient, StringRef(p, slen), radix);
 
-  // Compute how many bits are required.
+  // Compute how many bits are required. If the log is infinite, assume we need
-  return isNegative + tmp.logBase2() + 1;
+  // just bit.
+  unsigned log = tmp.logBase2();
+  if (log == (unsigned)-1) {
+    return isNegative + 1;
+  } else {
+    return isNegative + log + 1;
+  }
 }
 
 // From http://www.burtleburtle.net, byBob Jenkins.
@@ -2039,29 +2073,7 @@ void APInt::fromString(unsigned numbits, const StringRef& str, uint8_t radix) {
 
   // Enter digit traversal loop
   for (StringRef::iterator e = str.end(); p != e; ++p) {
-    // Get a digit
+    unsigned digit = getDigit(*p, radix);
-    unsigned digit = 0;
-    char cdigit = *p;
-    if (radix == 16) {
-      if (!isxdigit(cdigit))
-        llvm_unreachable("Invalid hex digit in string");
-      if (isdigit(cdigit))
-        digit = cdigit - '0';
-      else if (cdigit >= 'a')
-        digit = cdigit - 'a' + 10;
-      else if (cdigit >= 'A')
-        digit = cdigit - 'A' + 10;
-      else
-        llvm_unreachable("huh? we shouldn't get here");
-    } else if (isdigit(cdigit)) {
-      digit = cdigit - '0';
-      assert((radix == 10 ||
-              (radix == 8 && digit != 8 && digit != 9) ||
-              (radix == 2 && (digit == 0 || digit == 1))) &&
-             "Invalid digit in string for given radix");
-    } else {
-      llvm_unreachable("Invalid character in digit string");
-    }
 
     // Shift or multiply the value by the radix
     if (slen > 1) {

llvm/unittests/ADT/APIntTest.cpp

@@ -235,6 +235,88 @@ TEST(APIntTest, fromString) {
   EXPECT_EQ(APInt(32, -32), APInt(32, "-20", 16));
 }
 
+TEST(APIntTest, StringBitsNeeded2) {
+  EXPECT_EQ(1U, APInt::getBitsNeeded(  "0", 2));
+  EXPECT_EQ(1U, APInt::getBitsNeeded(  "1", 2));
+  EXPECT_EQ(2U, APInt::getBitsNeeded( "10", 2));
+  EXPECT_EQ(2U, APInt::getBitsNeeded( "11", 2));
+  EXPECT_EQ(3U, APInt::getBitsNeeded("100", 2));
+
+  EXPECT_EQ(1U, APInt::getBitsNeeded(  "+0", 2));
+  EXPECT_EQ(1U, APInt::getBitsNeeded(  "+1", 2));
+  EXPECT_EQ(2U, APInt::getBitsNeeded( "+10", 2));
+  EXPECT_EQ(2U, APInt::getBitsNeeded( "+11", 2));
+  EXPECT_EQ(3U, APInt::getBitsNeeded("+100", 2));
+
+  EXPECT_EQ(2U, APInt::getBitsNeeded(  "-0", 2));
+  EXPECT_EQ(2U, APInt::getBitsNeeded(  "-1", 2));
+  EXPECT_EQ(3U, APInt::getBitsNeeded( "-10", 2));
+  EXPECT_EQ(3U, APInt::getBitsNeeded( "-11", 2));
+  EXPECT_EQ(4U, APInt::getBitsNeeded("-100", 2));
+}
+
+TEST(APIntTest, StringBitsNeeded8) {
+  EXPECT_EQ(3U, APInt::getBitsNeeded( "0", 8));
+  EXPECT_EQ(3U, APInt::getBitsNeeded( "7", 8));
+  EXPECT_EQ(6U, APInt::getBitsNeeded("10", 8));
+  EXPECT_EQ(6U, APInt::getBitsNeeded("17", 8));
+  EXPECT_EQ(6U, APInt::getBitsNeeded("20", 8));
+
+  EXPECT_EQ(3U, APInt::getBitsNeeded( "+0", 8));
+  EXPECT_EQ(3U, APInt::getBitsNeeded( "+7", 8));
+  EXPECT_EQ(6U, APInt::getBitsNeeded("+10", 8));
+  EXPECT_EQ(6U, APInt::getBitsNeeded("+17", 8));
+  EXPECT_EQ(6U, APInt::getBitsNeeded("+20", 8));
+
+  EXPECT_EQ(4U, APInt::getBitsNeeded( "-0", 8));
+  EXPECT_EQ(4U, APInt::getBitsNeeded( "-7", 8));
+  EXPECT_EQ(7U, APInt::getBitsNeeded("-10", 8));
+  EXPECT_EQ(7U, APInt::getBitsNeeded("-17", 8));
+  EXPECT_EQ(7U, APInt::getBitsNeeded("-20", 8));
+}
+
+TEST(APIntTest, StringBitsNeeded10) {
+  EXPECT_EQ(1U, APInt::getBitsNeeded( "0", 10));
+  EXPECT_EQ(2U, APInt::getBitsNeeded( "3", 10));
+  EXPECT_EQ(4U, APInt::getBitsNeeded( "9", 10));
+  EXPECT_EQ(4U, APInt::getBitsNeeded("10", 10));
+  EXPECT_EQ(5U, APInt::getBitsNeeded("19", 10));
+  EXPECT_EQ(5U, APInt::getBitsNeeded("20", 10));
+
+  EXPECT_EQ(1U, APInt::getBitsNeeded( "+0", 10));
+  EXPECT_EQ(4U, APInt::getBitsNeeded( "+9", 10));
+  EXPECT_EQ(4U, APInt::getBitsNeeded("+10", 10));
+  EXPECT_EQ(5U, APInt::getBitsNeeded("+19", 10));
+  EXPECT_EQ(5U, APInt::getBitsNeeded("+20", 10));
+
+  EXPECT_EQ(2U, APInt::getBitsNeeded( "-0", 10));
+  EXPECT_EQ(5U, APInt::getBitsNeeded( "-9", 10));
+  EXPECT_EQ(5U, APInt::getBitsNeeded("-10", 10));
+  EXPECT_EQ(6U, APInt::getBitsNeeded("-19", 10));
+  EXPECT_EQ(6U, APInt::getBitsNeeded("-20", 10));
+}
+
+TEST(APIntTest, StringBitsNeeded16) {
+  EXPECT_EQ(4U, APInt::getBitsNeeded( "0", 16));
+  EXPECT_EQ(4U, APInt::getBitsNeeded( "F", 16));
+  EXPECT_EQ(8U, APInt::getBitsNeeded("10", 16));
+  EXPECT_EQ(8U, APInt::getBitsNeeded("1F", 16));
+  EXPECT_EQ(8U, APInt::getBitsNeeded("20", 16));
+
+  EXPECT_EQ(4U, APInt::getBitsNeeded( "+0", 16));
+  EXPECT_EQ(4U, APInt::getBitsNeeded( "+F", 16));
+  EXPECT_EQ(8U, APInt::getBitsNeeded("+10", 16));
+  EXPECT_EQ(8U, APInt::getBitsNeeded("+1F", 16));
+  EXPECT_EQ(8U, APInt::getBitsNeeded("+20", 16));
+
+  EXPECT_EQ(5U, APInt::getBitsNeeded( "-0", 16));
+  EXPECT_EQ(5U, APInt::getBitsNeeded( "-F", 16));
+  EXPECT_EQ(9U, APInt::getBitsNeeded("-10", 16));
+  EXPECT_EQ(9U, APInt::getBitsNeeded("-1F", 16));
+  EXPECT_EQ(9U, APInt::getBitsNeeded("-20", 16));
+}
+
+
 #ifdef GTEST_HAS_DEATH_TEST
 TEST(APIntTest, StringDeath) {
   EXPECT_DEATH(APInt(0, "", 0), "Bitwidth too small");