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Merged
cowtowncoder merged 2 commits into from
Mar 17, 2026
Merged

Use intrinsified Math.multiplyHigh() #1577

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8e4cef5
use intrinsified Math.multiplyHigh()
Mar 17, 2026
0189475
Add release notes
cowtowncoder Mar 17, 2026
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4 changes: 4 additions & 0 deletions release-notes/CREDITS
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Original file line number Diff line number Diff line change
Expand Up @@ -40,3 +40,7 @@ Rohan Nagendra (@rohan-repos)
* Reported #1553: Max Depth validation not working for `DataInput`-backed `JsonParser`s
in 3.0
(3.1.0)

Antonin Janec (@xtonik)
* Contributed #1576: Use Java 17 intrinstics for long multiplication
(3.2.0)
2 changes: 2 additions & 0 deletions release-notes/VERSION
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Expand Up @@ -26,6 +26,8 @@ JSON library.
#1570: Fail parsing from `DataInput` if
`StreamReadConstraints.getMaxDocumentLength()` set
(fix by @cowtowncoder, w/ Claude code)
#1576: Use Java 17 intrinstics for long multiplication
(contributed by @xtonik)

3.1.1 (not yet released)

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11 changes: 5 additions & 6 deletions src/main/java/tools/jackson/core/io/schubfach/DoubleToDecimal.java
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Expand Up @@ -27,7 +27,6 @@
import static tools.jackson.core.io.schubfach.MathUtils.flog2pow10;
import static tools.jackson.core.io.schubfach.MathUtils.g0;
import static tools.jackson.core.io.schubfach.MathUtils.g1;
import static tools.jackson.core.io.schubfach.MathUtils.multiplyHigh;
import static tools.jackson.core.io.schubfach.MathUtils.pow10;

import static java.lang.Double.doubleToRawLongBits;
Expand Down Expand Up @@ -365,7 +364,7 @@ private int toDecimal(int q, long c, int dk) {
wpin iff w' = tp10 10^k in Rv
See section 9.4 of [1].
*/
long sp10 = 10 * multiplyHigh(s, 115_292_150_460_684_698L << 4);
long sp10 = 10 * Math.multiplyHigh(s, 115_292_150_460_684_698L << 4);
long tp10 = sp10 + 10;
boolean upin = vbl + out <= sp10 << 2;
boolean wpin = (tp10 << 2) + out <= vbr;
Expand Down Expand Up @@ -400,9 +399,9 @@ Computes rop(cp g 2^(-127)), where g = g1 2^63 + g0
See section 9.10 and figure 5 of [1].
*/
private static long rop(long g1, long g0, long cp) {
long x1 = multiplyHigh(g0, cp);
long x1 = Math.multiplyHigh(g0, cp);
long y0 = g1 * cp;
long y1 = multiplyHigh(g1, cp);
long y1 = Math.multiplyHigh(g1, cp);
long z = (y0 >>> 1) + x1;
long vbp = y1 + (z >>> 63);
return vbp | (z & MASK_63) + MASK_63 >>> 63;
Expand Down Expand Up @@ -446,7 +445,7 @@ private int toChars(long f, int e) {
and for n = 9, m = 8
floor(hm / 10^8) = floor(1_441_151_881 hm / 2^57)
*/
long hm = multiplyHigh(f, 193_428_131_138_340_668L) >>> 20;
long hm = Math.multiplyHigh(f, 193_428_131_138_340_668L) >>> 20;
int l = (int) (f - 100_000_000L * hm);
int h = (int) (hm * 1_441_151_881L >>> 57);
int m = (int) (hm - 100_000_000 * h);
Expand Down Expand Up @@ -547,7 +546,7 @@ private int y(int a) {
(a + 1) 2^n <= 10^8 2^28 < 10^17
For n = 17, m = 8 the table in section 10 of [1] leads to:
*/
return (int) (multiplyHigh(
return (int) (Math.multiplyHigh(
(long) (a + 1) << 28,
193_428_131_138_340_668L) >>> 20) - 1;
}
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5 changes: 2 additions & 3 deletions src/main/java/tools/jackson/core/io/schubfach/FloatToDecimal.java
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Expand Up @@ -26,7 +26,6 @@
import static tools.jackson.core.io.schubfach.MathUtils.flog10threeQuartersPow2;
import static tools.jackson.core.io.schubfach.MathUtils.flog2pow10;
import static tools.jackson.core.io.schubfach.MathUtils.g1;
import static tools.jackson.core.io.schubfach.MathUtils.multiplyHigh;
import static tools.jackson.core.io.schubfach.MathUtils.pow10;

import static java.lang.Float.floatToRawIntBits;
Expand Down Expand Up @@ -398,7 +397,7 @@ Computes rop(cp g 2^(-95))
See appendix and figure 8 of [1].
*/
private static int rop(long g, long cp) {
long x1 = multiplyHigh(g, cp);
long x1 = Math.multiplyHigh(g, cp);
long vbp = x1 >>> 31;
return (int) (vbp | (x1 & MASK_32) + MASK_32 >>> 32);
}
Expand Down Expand Up @@ -529,7 +528,7 @@ private int y(int a) {
(a + 1) 2^n <= 10^8 2^28 < 10^17
For n = 17, m = 8 the table in section 10 of [1] leads to:
*/
return (int) (multiplyHigh(
return (int) (Math.multiplyHigh(
(long) (a + 1) << 28,
193_428_131_138_340_668L) >>> 20) - 1;
}
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12 changes: 0 additions & 12 deletions src/main/java/tools/jackson/core/io/schubfach/MathUtils.java
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Expand Up @@ -185,18 +185,6 @@ public static long g0(int k) {
return g[k - K_MIN << 1 | 1];
}

//a Java port of https://github.com/plokhotnyuk/jsoniter-scala/blob/c70a293ac802dc2eb44165471d76d7df2d4657b6/jsoniter-scala-core/native/src/main/scala/com/github/plokhotnyuk/jsoniter_scala/core/JsonWriter.scala#L2027
static long multiplyHigh(long x, long y) {
// Karatsuba technique for two positive ints
long x2 = x & 0xFFFFFFFFL;
long y2 = y & 0xFFFFFFFFL;
long b = x2 * y2;
long x1 = x >>> 32;
long y1 = y >>> 32;
long a = x1 * y1;
return (((b >>> 32) + (x1 + x2) * (y1 + y2) - b - a) >>> 32) + a;
}

/*
The precomputed values for g1(int) and g0(int).
The first entry must be for an exponent of K_MIN or less.
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