[AsmWriter/APFloat] FP constant printing: Avoid usage of locale dependent snprinf

This should fix the bug https://bugs.llvm.org/show_bug.cgi?id=12906

To print the FP constant AsmWriter does the following:

  1) convert FP value to String (actually using snprintf function which is locale dependent).
  2) Convert String back to FP Value
  3) Compare original and got FP values. If they are not equal just dump as hex.

The problem happens on the 2nd step when APFloat does not expect group delimiter or
fraction delimiter other than period symbol and so on, which can be produced on the
first step if LLVM library is used in an environment with corresponding locale set.

To fix this issue the locale independent APFloat:toString function is used.
However it prints FP values slightly differently than snprintf does. Specifically
it suppress trailing zeros in significant, use capital E and so on.
It results in 117 test failures during make check.
To avoid this I've also updated APFloat.toString a bit to pass make check at least.

Reviewers: sberg, bogner, majnemer, sanjoy, timshen, rnk

Reviewed By: timshen, rnk

Subscribers: rnk, llvm-commits

Differential Revision: https://reviews.llvm.org/D32276

llvm-svn: 300943

2 files changed, 45 insertions, 31 deletions

diff --git a/llvm/lib/IR/AsmWriter.cpp b/llvm/lib/IR/AsmWriter.cpp
index d0b77e7218b..27f6e366876 100644
--- a/llvm/lib/IR/AsmWriter.cpp
+++ b/llvm/lib/IR/AsmWriter.cpp
@@ -1103,35 +1103,34 @@ static void WriteConstantInternal(raw_ostream &Out, const Constant *CV,
   }
 
   if (const ConstantFP *CFP = dyn_cast<ConstantFP>(CV)) {
-    if (&CFP->getValueAPF().getSemantics() == &APFloat::IEEEsingle() ||
-        &CFP->getValueAPF().getSemantics() == &APFloat::IEEEdouble()) {
+    const APFloat &APF = CFP->getValueAPF();
+    if (&APF.getSemantics() == &APFloat::IEEEsingle() ||
+        &APF.getSemantics() == &APFloat::IEEEdouble()) {
       // We would like to output the FP constant value in exponential notation,
       // but we cannot do this if doing so will lose precision.  Check here to
       // make sure that we only output it in exponential format if we can parse
       // the value back and get the same value.
       //
       bool ignored;
-      bool isDouble = &CFP->getValueAPF().getSemantics()==&APFloat::IEEEdouble();
-      bool isInf = CFP->getValueAPF().isInfinity();
-      bool isNaN = CFP->getValueAPF().isNaN();
+      bool isDouble = &APF.getSemantics() == &APFloat::IEEEdouble();
+      bool isInf = APF.isInfinity();
+      bool isNaN = APF.isNaN();
       if (!isInf && !isNaN) {
-        double Val = isDouble ? CFP->getValueAPF().convertToDouble() :
-                                CFP->getValueAPF().convertToFloat();
+        double Val = isDouble ? APF.convertToDouble() : APF.convertToFloat();
         SmallString<128> StrVal;
-        raw_svector_ostream(StrVal) << Val;
-
+        APF.toString(StrVal, 6, 0, false);
         // Check to make sure that the stringized number is not some string like
         // "Inf" or NaN, that atof will accept, but the lexer will not.  Check
         // that the string matches the "[-+]?[0-9]" regex.
         //
-        if ((StrVal[0] >= '0' && StrVal[0] <= '9') ||
-            ((StrVal[0] == '-' || StrVal[0] == '+') &&
-             (StrVal[1] >= '0' && StrVal[1] <= '9'))) {
-          // Reparse stringized version!
-          if (APFloat(APFloat::IEEEdouble(), StrVal).convertToDouble() == Val) {
-            Out << StrVal;
-            return;
-          }
+        assert((StrVal[0] >= '0' && StrVal[0] <= '9') ||
+               ((StrVal[0] == '-' || StrVal[0] == '+') &&
+                (StrVal[1] >= '0' && StrVal[1] <= '9')) &&
+                   "[-+]?[0-9] regex does not match!");
+        // Reparse stringized version!
+        if (APFloat(APFloat::IEEEdouble(), StrVal).convertToDouble() == Val) {
+          Out << StrVal;
+          return;
         }
       }
       // Otherwise we could not reparse it to exactly the same value, so we must
@@ -1140,7 +1139,7 @@ static void WriteConstantInternal(raw_ostream &Out, const Constant *CV,
       // x86, so we must not use these types.
       static_assert(sizeof(double) == sizeof(uint64_t),
                     "assuming that double is 64 bits!");
-      APFloat apf = CFP->getValueAPF();
+      APFloat apf = APF;
       // Floats are represented in ASCII IR as double, convert.
       if (!isDouble)
         apf.convert(APFloat::IEEEdouble(), APFloat::rmNearestTiesToEven,
@@ -1153,27 +1152,27 @@ static void WriteConstantInternal(raw_ostream &Out, const Constant *CV,
     // These appear as a magic letter identifying the type, then a
     // fixed number of hex digits.
     Out << "0x";
-    APInt API = CFP->getValueAPF().bitcastToAPInt();
-    if (&CFP->getValueAPF().getSemantics() == &APFloat::x87DoubleExtended()) {
+    APInt API = APF.bitcastToAPInt();
+    if (&APF.getSemantics() == &APFloat::x87DoubleExtended()) {
       Out << 'K';
       Out << format_hex_no_prefix(API.getHiBits(16).getZExtValue(), 4,
                                   /*Upper=*/true);
       Out << format_hex_no_prefix(API.getLoBits(64).getZExtValue(), 16,
                                   /*Upper=*/true);
       return;
-    } else if (&CFP->getValueAPF().getSemantics() == &APFloat::IEEEquad()) {
+    } else if (&APF.getSemantics() == &APFloat::IEEEquad()) {
       Out << 'L';
       Out << format_hex_no_prefix(API.getLoBits(64).getZExtValue(), 16,
                                   /*Upper=*/true);
       Out << format_hex_no_prefix(API.getHiBits(64).getZExtValue(), 16,
                                   /*Upper=*/true);
-    } else if (&CFP->getValueAPF().getSemantics() == &APFloat::PPCDoubleDouble()) {
+    } else if (&APF.getSemantics() == &APFloat::PPCDoubleDouble()) {
       Out << 'M';
       Out << format_hex_no_prefix(API.getLoBits(64).getZExtValue(), 16,
                                   /*Upper=*/true);
       Out << format_hex_no_prefix(API.getHiBits(64).getZExtValue(), 16,
                                   /*Upper=*/true);
-    } else if (&CFP->getValueAPF().getSemantics() == &APFloat::IEEEhalf()) {
+    } else if (&APF.getSemantics() == &APFloat::IEEEhalf()) {
       Out << 'H';
       Out << format_hex_no_prefix(API.getZExtValue(), 4,
                                   /*Upper=*/true);
diff --git a/llvm/lib/Support/APFloat.cpp b/llvm/lib/Support/APFloat.cpp
index c4c892f0352..e1e2c22e1df 100644
--- a/llvm/lib/Support/APFloat.cpp
+++ b/llvm/lib/Support/APFloat.cpp
@@ -3393,7 +3393,7 @@ namespace {
 }
 
 void IEEEFloat::toString(SmallVectorImpl<char> &Str, unsigned FormatPrecision,
-                         unsigned FormatMaxPadding) const {
+                         unsigned FormatMaxPadding, bool TruncateZero) const {
   switch (category) {
   case fcInfinity:
     if (isNegative())
@@ -3407,9 +3407,16 @@ void IEEEFloat::toString(SmallVectorImpl<char> &Str, unsigned FormatPrecision,
     if (isNegative())
       Str.push_back('-');
 
-    if (!FormatMaxPadding)
-      append(Str, "0.0E+0");
-    else
+    if (!FormatMaxPadding) {
+      if (TruncateZero)
+        append(Str, "0.0E+0");
+      else {
+        append(Str, "0.0");
+        if (FormatPrecision > 1)
+          Str.append(FormatPrecision - 1, '0');
+        append(Str, "e+00");
+      }
+    } else
       Str.push_back('0');
     return;
 
@@ -3543,12 +3550,16 @@ void IEEEFloat::toString(SmallVectorImpl<char> &Str, unsigned FormatPrecision,
 
     Str.push_back(buffer[NDigits-1]);
     Str.push_back('.');
-    if (NDigits == 1)
+    if (NDigits == 1 && TruncateZero)
       Str.push_back('0');
     else
       for (unsigned I = 1; I != NDigits; ++I)
         Str.push_back(buffer[NDigits-1-I]);
-    Str.push_back('E');
+    // Fill with zeros up to FormatPrecision.
+    if (!TruncateZero && FormatPrecision > NDigits - 1)
+      Str.append(FormatPrecision - NDigits + 1, '0');
+    // For !TruncateZero we use lower 'e'.
+    Str.push_back(TruncateZero ? 'E' : 'e');
 
     Str.push_back(exp >= 0 ? '+' : '-');
     if (exp < 0) exp = -exp;
@@ -3557,6 +3568,9 @@ void IEEEFloat::toString(SmallVectorImpl<char> &Str, unsigned FormatPrecision,
       expbuf.push_back((char) ('0' + (exp % 10)));
       exp /= 10;
     } while (exp);
+    // Exponent always at least two digits if we do not truncate zeros.
+    if (!TruncateZero && expbuf.size() < 2)
+      expbuf.push_back('0');
     for (unsigned I = 0, E = expbuf.size(); I != E; ++I)
       Str.push_back(expbuf[E-1-I]);
     return;
@@ -4362,10 +4376,11 @@ bool DoubleAPFloat::isInteger() const {
 
 void DoubleAPFloat::toString(SmallVectorImpl<char> &Str,
                              unsigned FormatPrecision,
-                             unsigned FormatMaxPadding) const {
+                             unsigned FormatMaxPadding,
+                             bool TruncateZero) const {
   assert(Semantics == &semPPCDoubleDouble && "Unexpected Semantics");
   APFloat(semPPCDoubleDoubleLegacy, bitcastToAPInt())
-      .toString(Str, FormatPrecision, FormatMaxPadding);
+      .toString(Str, FormatPrecision, FormatMaxPadding, TruncateZero);
 }
 
 bool DoubleAPFloat::getExactInverse(APFloat *inv) const {