1176375 - SIMD float64x2 comparisons are broken.

Status: RESOLVED FIXED

(Core :: JavaScript Engine, defect)

Description

[Jukka Jylänki]

Attachment: aa.js

STR:

1. Run the attached file in SpiderMonkey.

Observed: The file prints

a: x=-3.4028234663852886e+38, y=-2.5
b: x=-Infinity, y=1.401298464e-45
c: x=-1, y=-1
A: x=-3.4028234663852886e+38, y=-2.5
B: x=-Infinity, y=1.401298464324817e-45
C: x=-1, y=0

Expected: The file should print

a: x=-3.4028234663852886e+38, y=-2.5
b: x=-Infinity, y=1.401298464e-45
c: x=-1, y=0
A: x=-3.4028234663852886e+38, y=-2.5
B: x=-Infinity, y=1.401298464324817e-45
C: x=-1, y=0

The test case was written for SIMD.float64x2.greaterThan(), but changing the comparison e.g. to SIMD.float64x2.lessThan(), a similar issue occurs, so other comparison functions may be affected here.

Comment 1

[Benjamin Bouvier [:bbouvier] (inactive)]

This happens because we haven't updated our SIMD implementation to use the BoolX2 vector. In the former spec, this is correct with c being an int32x4: the result of comparing a.x and b.x (resp. a.y and b.y) would be copied in both c.x and c.y (resp. c.z and c.w).
I'll add the new Bool types.

Comment 2

[Jakob Stoklund Olesen [:jolesen]]

The current patches in Bug 1160971 add a Bool64x2 type which is used as the result of the Float64x2 comparison functions.

Comment 3

[Benjamin Bouvier [:bbouvier] (inactive)]

Fixed by bug 1160971:



var f64 = SIMD.Float64x2;
var f32 = SIMD.Float32x4;

function p64(s, n) {
    console.log(n + ': x=' + f64.extractLane(s, 0) + ', y=' + f64.extractLane(s, 1));
}
function p32(s, n) {
    console.log(n + ': x=' + f32.extractLane(s, 0) + ', y=' + f32.extractLane(s, 1));
}

var a = SIMD.Float64x2(-3.4028234663852886e+38,-2.5)
p64(a, 'a');
var b = SIMD.Float64x2(-Infinity,1.4012984639999999e-45)
p64(b, 'b');
var c = SIMD.Float64x2.greaterThan(a, b);
console.log('c: x=' + SIMD.Bool64x2.extractLane(c, 0) + ', y=' + SIMD.Bool64x2.extractLane(c, 1));

var a = SIMD.Float32x4(-3.4028234663852886e+38,-2.5)
p32(a, 'A');
var b = SIMD.Float32x4(-Infinity,1.4012984639999999e-45)
p32(b, 'B');
var c = SIMD.Float32x4.greaterThan(a, b);
console.log('C: x=' + SIMD.Bool32x4.extractLane(c, 0) + ', y=' + SIMD.Bool32x4.extractLane(c, 1));



// Output:
a: x=-3.4028234663852886e+38, y=-2.5
b: x=-Infinity, y=1.401298464e-45
c: x=true, y=false
A: x=-3.4028234663852886e+38, y=-2.5
B: x=-Infinity, y=1.401298464324817e-45
C: x=true, y=false