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Faster implementation of long and int rotation #10187

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1e4cad3
Faster implementation of long and int rotation
zbynek Nov 16, 2025
0bfc1ac
Remove unused mod operation
zbynek Nov 17, 2025
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21 changes: 6 additions & 15 deletions user/super/com/google/gwt/emul/java/lang/Integer.java
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Original file line number Diff line number Diff line change
Expand Up @@ -184,24 +184,15 @@ public static int reverseBytes(int i) {
}

public static int rotateLeft(int i, int distance) {
while (distance-- > 0) {
i = i << 1 | ((i < 0) ? 1 : 0);
}
return i;
int lowerBits = i >>> (SIZE - distance);
int upperBits = i << distance;
return upperBits | lowerBits;
}

public static int rotateRight(int i, int distance) {
int ui = i & MAX_VALUE; // avoid sign extension
int carry = (i < 0) ? 0x40000000 : 0; // MIN_VALUE rightshifted 1
while (distance-- > 0) {
int nextcarry = ui & 1;
ui = carry | (ui >> 1);
carry = (nextcarry == 0) ? 0 : 0x40000000;
}
if (carry != 0) {
ui = ui | MIN_VALUE;
}
return ui;
int upperBits = i << (SIZE - distance);
int lowerBits = i >>> distance;
return upperBits | lowerBits;
}

public static int signum(int i) {
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21 changes: 6 additions & 15 deletions user/super/com/google/gwt/emul/java/lang/Long.java
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Original file line number Diff line number Diff line change
Expand Up @@ -128,24 +128,15 @@ public static long reverseBytes(long l) {
}

public static long rotateLeft(long i, int distance) {
while (distance-- > 0) {
i = i << 1 | ((i < 0) ? 1 : 0);
}
return i;
long lowerBits = i >>> (SIZE - distance);
long upperBits = i << distance;
return upperBits | lowerBits;
}

public static long rotateRight(long i, int distance) {
long ui = i & MAX_VALUE; // avoid sign extension
long carry = (i < 0) ? 0x4000000000000000L : 0; // MIN_VALUE rightshifted 1
while (distance-- > 0) {
long nextcarry = ui & 1;
ui = carry | (ui >> 1);
carry = (nextcarry == 0) ? 0 : 0x4000000000000000L;
}
if (carry != 0) {
ui = ui | MIN_VALUE;
}
return ui;
long upperBits = i << (SIZE - distance);
long lowerBits = i >>> distance;
return upperBits | lowerBits;
}

public static int signum(long i) {
Expand Down
6 changes: 6 additions & 0 deletions user/test/com/google/gwt/emultest/java/lang/IntegerTest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -234,13 +234,19 @@ public void testRotateLeft() {
assertEquals(-1, Integer.rotateLeft(-1, 4));
assertEquals(Integer.MIN_VALUE, Integer.rotateLeft(0x40000000, 1));
assertEquals(1, Integer.rotateLeft(Integer.MIN_VALUE, 1));
assertEquals(Integer.MIN_VALUE, Integer.rotateLeft(Integer.MIN_VALUE, 0));
assertEquals(Integer.MIN_VALUE, Integer.rotateLeft(1, -1));
assertEquals(-1, Integer.rotateLeft(-1, 1000));
}

public void testRotateRight() {
assertEquals(0, Integer.rotateRight(0, 4));
assertEquals(Integer.MIN_VALUE, Integer.rotateRight(1, 1));
assertEquals(0x10000000, Integer.rotateRight(1, 4));
assertEquals(-1, Integer.rotateRight(-1, 4));
assertEquals(Integer.MIN_VALUE, Integer.rotateLeft(Integer.MIN_VALUE, 0));
assertEquals(1, Integer.rotateRight(Integer.MIN_VALUE, -1));
assertEquals(-1, Integer.rotateRight(-1, 1000));
}

public void testSignum() {
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6 changes: 6 additions & 0 deletions user/test/com/google/gwt/emultest/java/lang/LongTest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -224,13 +224,19 @@ public void testRotateLeft() {
assertEquals(-1, Long.rotateLeft(-1, 4));
assertEquals(Long.MIN_VALUE, Long.rotateLeft(0x4000000000000000L, 1));
assertEquals(1, Long.rotateLeft(Long.MIN_VALUE, 1));
assertEquals(Long.MIN_VALUE, Long.rotateLeft(Long.MIN_VALUE, 0));
assertEquals(Long.MIN_VALUE, Long.rotateLeft(1, -1));
assertEquals(-1, Long.rotateLeft(-1, 1000));
}

public void testRotateRight() {
assertEquals(0, Long.rotateRight(0, 4));
assertEquals(Long.MIN_VALUE, Long.rotateRight(1, 1));
assertEquals(0x1000000000000000L, Long.rotateRight(1, 4));
assertEquals(-1, Long.rotateRight(-1, 4));
assertEquals(Long.MIN_VALUE, Long.rotateRight(Long.MIN_VALUE, 0));
assertEquals(1, Long.rotateRight(Long.MIN_VALUE, -1));
assertEquals(-1, Long.rotateRight(-1, 1000));
}

public void testSignum() {
Expand Down
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