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Fix IntegerUtil#getDivisorNumbers

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Use unsigned mod operation for initialization of anc

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- 5a0cefb45e
- acc8ed9634
This commit is contained in:
Spottedleaf 2023-06-16 09:05:36 -07:00
parent 02e3b5a91a
commit 3f237e869a
3 changed files with 68 additions and 17 deletions
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28
patches/server/0009-MC-Utils.patch
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@ -3111,10 +3111,10 @@ index 0000000000000000000000000000000000000000..413e4b6da027876dbbe8eb78f2568a44
+}
diff --git a/src/main/java/io/papermc/paper/util/IntegerUtil.java b/src/main/java/io/papermc/paper/util/IntegerUtil.java
new file mode 100644
index 0000000000000000000000000000000000000000..a1bc1d1d0c86217ef18883d281195bc6b27e52ac
index 0000000000000000000000000000000000000000..16785bd5c0524f6bad0691ca7ecd4514608d2eab
--- /dev/null
+++ b/src/main/java/io/papermc/paper/util/IntegerUtil.java
@@ -0,0 +1,226 @@
@@ -0,0 +1,242 @@
+package io.papermc.paper.util;
+
+public final class IntegerUtil {
@ -3214,7 +3214,7 @@ index 0000000000000000000000000000000000000000..a1bc1d1d0c86217ef18883d281195bc6
+ // copied from hacker's delight (signed division magic value)
+ // http://www.hackersdelight.org/hdcodetxt/magic.c.txt
+ public static long getDivisorNumbers(final int d) {
+ final int ad = IntegerUtil.branchlessAbs(d);
+ final int ad = branchlessAbs(d);
+
+ if (ad < 2) {
+ throw new IllegalArgumentException("|number| must be in [2, 2^31 -1], not: " + d);
@ -3223,11 +3223,27 @@ index 0000000000000000000000000000000000000000..a1bc1d1d0c86217ef18883d281195bc6
+ final int two31 = 0x80000000;
+ final long mask = 0xFFFFFFFFL; // mask for enforcing unsigned behaviour
+
+ /*
+ Signed usage:
+ int number;
+ long magic = getDivisorNumbers(div);
+ long mul = magic >>> 32;
+ int sign = number >> 31;
+ int result = (int)(((long)number * mul) >>> magic) - sign;
+ */
+ /*
+ Unsigned usage:
+ int number;
+ long magic = getDivisorNumbers(div);
+ long mul = magic >>> 32;
+ int result = (int)(((long)number * mul) >>> magic);
+ */
+
+ int p = 31;
+
+ // all these variables are UNSIGNED!
+ int t = two31 + (d >>> 31);
+ int anc = t - 1 - t%ad;
+ int anc = t - 1 - (int)((t & mask)%ad);
+ int q1 = (int)((two31 & mask)/(anc & mask));
+ int r1 = two31 - q1*anc;
+ int q2 = (int)((two31 & mask)/(ad & mask));
@ -3255,7 +3271,7 @@ index 0000000000000000000000000000000000000000..a1bc1d1d0c86217ef18883d281195bc6
+ if (d < 0) {
+ magicNum = -magicNum;
+ }
+ int shift = p - 32;
+ int shift = p;
+ return ((long)magicNum << 32) | shift;
+ }
+
@ -6690,7 +6706,7 @@ index a0b5895abc88d297045e05f25bb09527991d43f0..6e0bd0eab0b06a4ac3042496bbb91292
super(type, world);
this.xpReward = 5;
diff --git a/src/main/java/net/minecraft/world/item/ItemStack.java b/src/main/java/net/minecraft/world/item/ItemStack.java
index 6375dfa336d232c7876e184690a1cb5c9bc2c495..2e948330c4951e3df7091fa870573f163d2af286 100644
index a797c6dd17cf73feada7badccf47b4036f746405..6758e72177c0a407cf6c392b10263f095e4d06e8 100644
--- a/src/main/java/net/minecraft/world/item/ItemStack.java
+++ b/src/main/java/net/minecraft/world/item/ItemStack.java
@@ -788,6 +788,25 @@ public final class ItemStack {