diff options
Diffstat (limited to 'src/wasm/literal.cpp')
| -rw-r--r-- | src/wasm/literal.cpp | 36 |
1 files changed, 9 insertions, 27 deletions
diff --git a/src/wasm/literal.cpp b/src/wasm/literal.cpp index 684108581..843f4607f 100644 --- a/src/wasm/literal.cpp +++ b/src/wasm/literal.cpp @@ -859,38 +859,20 @@ Literal Literal::demote() const { return Literal(float(getf64())); } -// Wasm has nondeterministic rules for NaN propagation in some operations. For -// example. f32.neg is deterministic and just flips the sign, even of a NaN, but -// f32.add is nondeterministic, and if one or more of the inputs is a NaN, then -// -// * if all NaNs are canonical NaNs, the output is some arbitrary canonical NaN -// * otherwise the output is some arbitrary arithmetic NaN -// -// (canonical = NaN payload is 1000..000; arithmetic: 1???..???, that is, the -// high bit is 1 and all others can be 0 or 1) -// -// For many things we don't need to care, and can just do a normal C++ add for -// an f32.add, for example - the wasm rules are specified so that things like -// that just work (in order for such math to be fast). However, for our -// optimizer, it is useful to "standardize" NaNs when there is nondeterminism. -// That is, when there are multiple valid outputs, it's nice to emit the same -// one consistently, so that it doesn't look like the optimization changed -// something. In other words, if the valid output of an expression is a set of -// valid NaNs, and after optimization the output is still that same set, then -// the optimization is valid. And if the interpreter picks the same NaN in both -// cases from that identical set then nothing looks wrong to the fuzzer. -template<typename T> static Literal standardizeNaN(T result) { +Literal standardizeNaN(float result) { if (!std::isnan(result)) { return Literal(result); } // Pick a simple canonical payload, and positive. - if (sizeof(T) == 4) { - return Literal(Literal(uint32_t(0x7fc00000u)).reinterpretf32()); - } else if (sizeof(T) == 8) { - return Literal(Literal(uint64_t(0x7ff8000000000000ull)).reinterpretf64()); - } else { - WASM_UNREACHABLE("invalid float"); + return Literal(Literal(uint32_t(0x7fc00000u)).reinterpretf32()); +} + +Literal standardizeNaN(double result) { + if (!std::isnan(result)) { + return Literal(result); } + // Pick a simple canonical payload, and positive. + return Literal(Literal(uint64_t(0x7ff8000000000000ull)).reinterpretf64()); } Literal Literal::add(const Literal& other) const { |