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Fix NaN / 0 #442

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Merged
jfbastien merged 1 commit into from
May 5, 2016
Merged

Fix NaN / 0 #442

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34 changes: 30 additions & 4 deletions src/wasm.h
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Original file line number Diff line number Diff line change
Expand Up @@ -246,11 +246,37 @@ class Literal {
}
}

static uint32_t NaNPayload(float f) {
assert(std::isnan(f) && "expected a NaN");
// SEEEEEEE EFFFFFFF FFFFFFFF FFFFFFFF
// NaN has all-one exponent and non-zero fraction.
return ~0xff800000u & bit_cast<uint32_t>(f);
}

static uint64_t NaNPayload(double f) {
assert(std::isnan(f) && "expected a NaN");
// SEEEEEEE EEEEFFFF FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF
// NaN has all-one exponent and non-zero fraction.
return ~0xfff0000000000000ull & bit_cast<uint64_t>(f);
}

static float setQuietNaN(float f) {
assert(std::isnan(f) && "expected a NaN");
// An SNaN is a NaN with the most significant fraction bit clear.
return bit_cast<float>(0x00400000u | bit_cast<uint32_t>(f));
}

static double setQuietNaN(double f) {
assert(std::isnan(f) && "expected a NaN");
// An SNaN is a NaN with the most significant fraction bit clear.
return bit_cast<double>(0x0008000000000000ull | bit_cast<uint64_t>(f));
}

static void printFloat(std::ostream &o, float f) {
if (std::isnan(f)) {
const char *sign = std::signbit(f) ? "-" : "";
o << sign << "nan";
if (uint32_t payload = ~0xff800000u & bit_cast<uint32_t>(f)) {
if (uint32_t payload = NaNPayload(f)) {
o << ":0x" << std::hex << payload << std::dec;
}
return;
Expand All @@ -266,7 +292,7 @@ class Literal {
if (std::isnan(d)) {
const char *sign = std::signbit(d) ? "-" : "";
o << sign << "nan";
if (uint64_t payload = ~0xfff0000000000000ull & bit_cast<uint64_t>(d)) {
if (uint64_t payload = NaNPayload(d)) {
o << ":0x" << std::hex << payload << std::dec;
}
return;
Expand Down Expand Up @@ -448,7 +474,7 @@ class Literal {
switch (std::fpclassify(rhs)) {
case FP_ZERO:
switch (std::fpclassify(lhs)) {
case FP_NAN: return *this;
case FP_NAN: return Literal(setQuietNaN(lhs));
case FP_ZERO: return Literal(std::copysign(std::numeric_limits<float>::quiet_NaN(), sign));
case FP_NORMAL: // fallthrough
case FP_SUBNORMAL: // fallthrough
Expand All @@ -468,7 +494,7 @@ class Literal {
switch (std::fpclassify(rhs)) {
case FP_ZERO:
switch (std::fpclassify(lhs)) {
case FP_NAN: return *this;
case FP_NAN: return Literal(setQuietNaN(lhs));
case FP_ZERO: return Literal(std::copysign(std::numeric_limits<double>::quiet_NaN(), sign));
case FP_NORMAL: // fallthrough
case FP_SUBNORMAL: // fallthrough
Expand Down