diff options
| -rw-r--r-- | src/tools/wasm2js.cpp | 42 | ||||
| -rw-r--r-- | test/wasm2js/br_table_temp.2asm.js.opt | 2 | ||||
| -rw-r--r-- | test/wasm2js/emscripten.2asm.js.opt | 14 |
3 files changed, 34 insertions, 24 deletions
diff --git a/src/tools/wasm2js.cpp b/src/tools/wasm2js.cpp index fb63627a3..d64f0b0ab 100644 --- a/src/tools/wasm2js.cpp +++ b/src/tools/wasm2js.cpp @@ -260,23 +260,33 @@ static void optimizeJS(Ref ast, Wasm2JSBuilder::Flags flags) { node[0]->setString(UNARY_PREFIX); node[1]->setString(L_NOT); node[3]->setNull(); - } else if (isOrZero(node) || isTrshiftZero(node)) { - // Just being different from 0 is enough, casts don't matter. However, - // in deterministic mode we care about corner cases that would trap in - // wasm, like an integer divide by zero: - // - // if ((1 / 0) | 0) => condition is Infinity | 0 = 0 which is falsey - // - // while - // - // if (1 / 0) => condition is Infinity which is truthy - // - // Thankfully this is not common, and does not occur on % (1 % 0 is a NaN - // which has the right truthiness). - if (!(flags.deterministic && isBinary(node[2], DIV))) { - return node[2]; - } } + // TODO: in some cases it may be possible to turn + // + // if (x | 0) + // + // into + // + // if (x) + // + // In general this is unsafe if e.g. x is -2147483648 + -2147483648 (which + // the | 0 turns into 0, but without it is a truthy value). + // + // Another issue is that in deterministic mode we care about corner cases + // that would trap in wasm, like an integer divide by zero: + // + // if ((1 / 0) | 0) => condition is Infinity | 0 = 0 which is falsey + // + // while + // + // if (1 / 0) => condition is Infinity which is truthy + // + // Thankfully this is not common, and does not occur on % (1 % 0 is a NaN + // which has the right truthiness), so we could perhaps do + // + // if (!(flags.deterministic && isBinary(node[2], DIV))) return node[2]; + // + // (but there is still the first issue). return node; }; diff --git a/test/wasm2js/br_table_temp.2asm.js.opt b/test/wasm2js/br_table_temp.2asm.js.opt index eba815912..f588a3430 100644 --- a/test/wasm2js/br_table_temp.2asm.js.opt +++ b/test/wasm2js/br_table_temp.2asm.js.opt @@ -12619,7 +12619,7 @@ function asmFunc(global, env, buffer) { function $63($0) { $0 = $0 | 0; - if ($0 - 1) { + if ($0 - 1 | 0) { $0 = 9 } else { $0 = 8 diff --git a/test/wasm2js/emscripten.2asm.js.opt b/test/wasm2js/emscripten.2asm.js.opt index d697fa7c7..35f2958e0 100644 --- a/test/wasm2js/emscripten.2asm.js.opt +++ b/test/wasm2js/emscripten.2asm.js.opt @@ -83,34 +83,34 @@ function asmFunc(global, env, buffer) { if (HEAPU8[144] < 3) { bar() } - if (bools(314159) >>> 7) { + if (bools(314159) >>> 7 | 0) { bar() } if (bools(314159) >> 8) { bar() } - if (~~getf32()) { + if (~~getf32() >>> 0) { bar() } if (~~getf32()) { bar() } - if (~~getf64()) { + if (~~getf64() >>> 0) { bar() } if (~~getf64()) { bar() } - if ((geti32() + geti32() | 0) + geti32()) { + if ((geti32() + geti32() | 0) + geti32() | 0) { bar() } - if (geti32() + (geti32() + geti32() | 0)) { + if (geti32() + (geti32() + geti32() | 0) | 0) { bar() } - if (geti32() + geti32() + (geti32() + geti32())) { + if (geti32() + geti32() + (geti32() + geti32()) | 0) { bar() } - if (geti32() + geti32() + (geti32() + geti32()) + (geti32() + geti32() + (geti32() + geti32()))) { + if (geti32() + geti32() + (geti32() + geti32()) + (geti32() + geti32() + (geti32() + geti32())) | 0) { bar() } } |