diff --git a/packages/compiler/src/backend/llvm/integer-values.ts b/packages/compiler/src/backend/llvm/integer-values.ts index 7d5e241dc..90954f4c6 100644 --- a/packages/compiler/src/backend/llvm/integer-values.ts +++ b/packages/compiler/src/backend/llvm/integer-values.ts @@ -65,6 +65,22 @@ function magnitude(range: IntegerRange): number { return Math.max(Math.abs(range.min), Math.abs(range.max)); } +/** The bounds of a sum and a product of two magnitude bounds, as doubles. + * Below 2^53 the double result is the integer; above it the result is past + * every exactness limit either way, and rounding moves it far less than the + * margin from WIDE_BOUND to the i64 range. A result of exactly 2^53 may + * stand for 2^53 + 1 (2^53 - 1 + 2 rounds to 2^53), so it moves to the next + * double up unless the sum is exactly 2^53. */ +function sumBound(a: number, b: number): number { + const sum = a + b; + return sum === EXACT_DOUBLES && EXACT_DOUBLES - a !== b ? sum + 2 : sum; +} + +function productBound(a: number, b: number): number { + const product = a * b; + return product === EXACT_DOUBLES ? product + 2 : product; +} + /** The wide view of `l op r` for `+`, `-` and `*` when the exact operands * have no proven result range (their product or sum may pass 2^53). * @@ -98,14 +114,14 @@ export function wideArithmetic( if (op === "*") { if (lv.below !== Infinity || rv.below !== Infinity) return null; below = EXACT_DOUBLES; - bound = lv.bound * rv.bound; + bound = productBound(lv.bound, rv.bound); } else if (lv.below === Infinity && rv.below === Infinity) { below = EXACT_DOUBLES; - bound = lv.bound + rv.bound; + bound = sumBound(lv.bound, rv.bound); } else if (lv.below === Infinity || rv.below === Infinity) { const [exact, wide] = lv.below === Infinity ? [lv, rv] : [rv, lv]; below = Math.min(wide.below - exact.bound, EXACT_DOUBLES); - bound = exact.bound + wide.bound; + bound = sumBound(exact.bound, wide.bound); } else return null; if (!(bound <= WIDE_BOUND) || below < INDEX_LIMIT) return null; const operand = (value: LlValue, integer: LlInteger | null): string => diff --git a/tests/corpus/7982-integer-view-compares.ts b/tests/corpus/7982-integer-view-compares.ts index db224aff1..5978eaf86 100644 --- a/tests/corpus/7982-integer-view-compares.ts +++ b/tests/corpus/7982-integer-view-compares.ts @@ -60,6 +60,20 @@ function nearLimit(start: number): string { return seen.join(" "); } +function atLimit(start: number, end: number): string { + // A counter of integer locals only, up to 2^53 - 1: `i + 2` may be + // 2^53 + 1, whose double is 2^53, so `i + 1 === i + 2` holds at the end. + let same = 0; + let above = 0; + let mixed = 0; + for (let i = start; i <= end; i++) { + if (i + 1 === i + 2) same++; + if (i + 2 > 9007199254740992) above++; + mixed += (i * 2) % 3; + } + return `${same} ${above} ${mixed}`; +} + console.log(heapSort(new Int32Array([5, -3, 9, 0, 9, 2147483647, -2147483648, 7, 1]))); console.log(heapSort(new Int32Array([])), heapSort(new Int32Array([4]))); console.log(neighbors(new Float64Array([1, 2, 3, 4]))); @@ -67,3 +81,5 @@ const sorted = new Int32Array([-5, -1, 0, 0, 3, 8, 8, 13]); console.log([-6, -1, 0, 1, 8, 13, 14].map((v) => lowerBound(sorted, v)).join()); console.log(nearLimit(9007199254740988)); console.log(nearLimit(-9007199254740991)); +console.log(atLimit(9007199254740988, 9007199254740991)); +console.log(atLimit(-9007199254740991, -9007199254740988));