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compiler_rt: Add trunc f128 narrowing functions

master
Marc Tiehuis 2018-06-28 20:26:35 +12:00
parent a3ab4325fd
commit 379950f81d
2 changed files with 115 additions and 39 deletions
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16
std/special/compiler_rt/truncXfYf2.zig
View File

@ -4,7 +4,13 @@ pub extern fn __truncsfhf2(a: f32) u16 {
return @bitCast(u16, truncXfYf2(f16, f32, a));
}
const CHAR_BIT = 8;
pub extern fn __trunctfsf2(a: f128) f32 {
return truncXfYf2(f32, f128, a);
}
pub extern fn __trunctfdf2(a: f128) f64 {
return truncXfYf2(f64, f128, a);
}
inline fn truncXfYf2(comptime dst_t: type, comptime src_t: type, a: src_t) dst_t {
const src_rep_t = @IntType(false, @typeInfo(src_t).Float.bits);
@ -16,7 +22,7 @@ inline fn truncXfYf2(comptime dst_t: type, comptime src_t: type, a: src_t) dst_t
// Various constants whose values follow from the type parameters.
// Any reasonable optimizer will fold and propagate all of these.
const srcBits = @sizeOf(src_t) * CHAR_BIT;
const srcBits = src_t.bit_count;
const srcExpBits = srcBits - srcSigBits - 1;
const srcInfExp = (1 << srcExpBits) - 1;
const srcExpBias = srcInfExp >> 1;
@ -31,7 +37,7 @@ inline fn truncXfYf2(comptime dst_t: type, comptime src_t: type, a: src_t) dst_t
const srcQNaN = 1 << (srcSigBits - 1);
const srcNaNCode = srcQNaN - 1;
const dstBits = @sizeOf(dst_t) * CHAR_BIT;
const dstBits = dst_t.bit_count;
const dstExpBits = dstBits - dstSigBits - 1;
const dstInfExp = (1 << dstExpBits) - 1;
const dstExpBias = dstInfExp >> 1;
@ -79,8 +85,8 @@ inline fn truncXfYf2(comptime dst_t: type, comptime src_t: type, a: src_t) dst_t
// a underflows on conversion to the destination type or is an exact
// zero. The result may be a denormal or zero. Extract the exponent
// to get the shift amount for the denormalization.
const aExp: u32 = aAbs >> srcSigBits;
const shift: u32 = srcExpBias - dstExpBias - aExp + 1;
const aExp = aAbs >> srcSigBits;
const shift = srcExpBias - dstExpBias - aExp + 1;
const significand: src_rep_t = (aRep & srcSignificandMask) | srcMinNormal;

138
std/special/compiler_rt/truncXfYf2_test.zig
View File

@ -11,54 +11,124 @@ fn test__truncsfhf2(a: u32, expected: u16) void {
}
test "truncsfhf2" {
test__truncsfhf2(0x7fc00000, 0x7e00); // qNaN
test__truncsfhf2(0x7fe00000, 0x7f00); // sNaN
test__truncsfhf2(0x7fc00000, 0x7e00); // qNaN
test__truncsfhf2(0x7fe00000, 0x7f00); // sNaN
test__truncsfhf2(0, 0); // 0
test__truncsfhf2(0x80000000, 0x8000); // -0
test__truncsfhf2(0, 0); // 0
test__truncsfhf2(0x80000000, 0x8000); // -0
test__truncsfhf2(0x7f800000, 0x7c00); // inf
test__truncsfhf2(0xff800000, 0xfc00); // -inf
test__truncsfhf2(0x7f800000, 0x7c00); // inf
test__truncsfhf2(0xff800000, 0xfc00); // -inf
test__truncsfhf2(0x477ff000, 0x7c00); // 65520 -> inf
test__truncsfhf2(0xc77ff000, 0xfc00); // -65520 -> -inf
test__truncsfhf2(0x477ff000, 0x7c00); // 65520 -> inf
test__truncsfhf2(0xc77ff000, 0xfc00); // -65520 -> -inf
test__truncsfhf2(0x71cc3892, 0x7c00); // 0x1.987124876876324p+100 -> inf
test__truncsfhf2(0xf1cc3892, 0xfc00); // -0x1.987124876876324p+100 -> -inf
test__truncsfhf2(0x71cc3892, 0x7c00); // 0x1.987124876876324p+100 -> inf
test__truncsfhf2(0xf1cc3892, 0xfc00); // -0x1.987124876876324p+100 -> -inf
test__truncsfhf2(0x38800000, 0x0400); // normal (min), 2**-14
test__truncsfhf2(0xb8800000, 0x8400); // normal (min), -2**-14
test__truncsfhf2(0x38800000, 0x0400); // normal (min), 2**-14
test__truncsfhf2(0xb8800000, 0x8400); // normal (min), -2**-14
test__truncsfhf2(0x477fe000, 0x7bff); // normal (max), 65504
test__truncsfhf2(0xc77fe000, 0xfbff); // normal (max), -65504
test__truncsfhf2(0x477fe000, 0x7bff); // normal (max), 65504
test__truncsfhf2(0xc77fe000, 0xfbff); // normal (max), -65504
test__truncsfhf2(0x477fe100, 0x7bff); // normal, 65505 -> 65504
test__truncsfhf2(0xc77fe100, 0xfbff); // normal, -65505 -> -65504
test__truncsfhf2(0x477fe100, 0x7bff); // normal, 65505 -> 65504
test__truncsfhf2(0xc77fe100, 0xfbff); // normal, -65505 -> -65504
test__truncsfhf2(0x477fef00, 0x7bff); // normal, 65519 -> 65504
test__truncsfhf2(0xc77fef00, 0xfbff); // normal, -65519 -> -65504
test__truncsfhf2(0x477fef00, 0x7bff); // normal, 65519 -> 65504
test__truncsfhf2(0xc77fef00, 0xfbff); // normal, -65519 -> -65504
test__truncsfhf2(0x3f802000, 0x3c01); // normal, 1 + 2**-10
test__truncsfhf2(0xbf802000, 0xbc01); // normal, -1 - 2**-10
test__truncsfhf2(0x3f802000, 0x3c01); // normal, 1 + 2**-10
test__truncsfhf2(0xbf802000, 0xbc01); // normal, -1 - 2**-10
test__truncsfhf2(0x3eaaa000, 0x3555); // normal, approx. 1/3
test__truncsfhf2(0xbeaaa000, 0xb555); // normal, approx. -1/3
test__truncsfhf2(0x3eaaa000, 0x3555); // normal, approx. 1/3
test__truncsfhf2(0xbeaaa000, 0xb555); // normal, approx. -1/3
test__truncsfhf2(0x40490fdb, 0x4248); // normal, 3.1415926535
test__truncsfhf2(0xc0490fdb, 0xc248); // normal, -3.1415926535
test__truncsfhf2(0x40490fdb, 0x4248); // normal, 3.1415926535
test__truncsfhf2(0xc0490fdb, 0xc248); // normal, -3.1415926535
test__truncsfhf2(0x45cc3892, 0x6e62); // normal, 0x1.987124876876324p+12
test__truncsfhf2(0x45cc3892, 0x6e62); // normal, 0x1.987124876876324p+12
test__truncsfhf2(0x3f800000, 0x3c00); // normal, 1
test__truncsfhf2(0x38800000, 0x0400); // normal, 0x1.0p-14
test__truncsfhf2(0x3f800000, 0x3c00); // normal, 1
test__truncsfhf2(0x38800000, 0x0400); // normal, 0x1.0p-14
test__truncsfhf2(0x33800000, 0x0001); // denormal (min), 2**-24
test__truncsfhf2(0xb3800000, 0x8001); // denormal (min), -2**-24
test__truncsfhf2(0x33800000, 0x0001); // denormal (min), 2**-24
test__truncsfhf2(0xb3800000, 0x8001); // denormal (min), -2**-24
test__truncsfhf2(0x387fc000, 0x03ff); // denormal (max), 2**-14 - 2**-24
test__truncsfhf2(0xb87fc000, 0x83ff); // denormal (max), -2**-14 + 2**-24
test__truncsfhf2(0x387fc000, 0x03ff); // denormal (max), 2**-14 - 2**-24
test__truncsfhf2(0xb87fc000, 0x83ff); // denormal (max), -2**-14 + 2**-24
test__truncsfhf2(0x35800000, 0x0010); // denormal, 0x1.0p-20
test__truncsfhf2(0x33280000, 0x0001); // denormal, 0x1.5p-25 -> 0x1.0p-24
test__truncsfhf2(0x33000000, 0x0000); // 0x1.0p-25 -> zero
test__truncsfhf2(0x35800000, 0x0010); // denormal, 0x1.0p-20
test__truncsfhf2(0x33280000, 0x0001); // denormal, 0x1.5p-25 -> 0x1.0p-24
test__truncsfhf2(0x33000000, 0x0000); // 0x1.0p-25 -> zero
}
const __trunctfsf2 = @import("truncXfYf2.zig").__trunctfsf2;
fn test__trunctfsf2(a: f128, expected: u32) void {
const x = __trunctfsf2(a);
const rep = @bitCast(u32, x);
if (rep == expected) {
return;
}
// test other possible NaN representation(signal NaN)
else if (expected == 0x7fc00000) {
if ((rep & 0x7f800000) == 0x7f800000 and (rep & 0x7fffff) > 0) {
return;
}
}
@panic("__trunctfsf2 test failure");
}
test "trunctfsf2" {
// qnan
test__trunctfsf2(@bitCast(f128, u128(0x7fff800000000000 << 64)), 0x7fc00000);
// nan
test__trunctfsf2(@bitCast(f128, u128((0x7fff000000000000 | (0x810000000000 & 0xffffffffffff)) << 64)), 0x7fc08000);
// inf
test__trunctfsf2(@bitCast(f128, u128(0x7fff000000000000 << 64)), 0x7f800000);
// zero
test__trunctfsf2(0.0, 0x0);
test__trunctfsf2(0x1.23a2abb4a2ddee355f36789abcdep+5, 0x4211d156);
test__trunctfsf2(0x1.e3d3c45bd3abfd98b76a54cc321fp-9, 0x3b71e9e2);
test__trunctfsf2(0x1.234eebb5faa678f4488693abcdefp+4534, 0x7f800000);
test__trunctfsf2(0x1.edcba9bb8c76a5a43dd21f334634p-435, 0x0);
}
const __trunctfdf2 = @import("truncXfYf2.zig").__trunctfdf2;
fn test__trunctfdf2(a: f128, expected: u64) void {
const x = __trunctfdf2(a);
const rep = @bitCast(u64, x);
if (rep == expected) {
return;
}
// test other possible NaN representation(signal NaN)
else if (expected == 0x7ff8000000000000) {
if ((rep & 0x7ff0000000000000) == 0x7ff0000000000000 and (rep & 0xfffffffffffff) > 0) {
return;
}
}
@panic("__trunctfsf2 test failure");
}
test "trunctfdf2" {
// qnan
test__trunctfdf2(@bitCast(f128, u128(0x7fff800000000000 << 64)), 0x7ff8000000000000);
// nan
test__trunctfdf2(@bitCast(f128, u128((0x7fff000000000000 | (0x810000000000 & 0xffffffffffff)) << 64)), 0x7ff8100000000000);
// inf
test__trunctfdf2(@bitCast(f128, u128(0x7fff000000000000 << 64)), 0x7ff0000000000000);
// zero
test__trunctfdf2(0.0, 0x0);
test__trunctfdf2(0x1.af23456789bbaaab347645365cdep+5, 0x404af23456789bbb);
test__trunctfdf2(0x1.dedafcff354b6ae9758763545432p-9, 0x3f6dedafcff354b7);
test__trunctfdf2(0x1.2f34dd5f437e849b4baab754cdefp+4534, 0x7ff0000000000000);
test__trunctfdf2(0x1.edcbff8ad76ab5bf46463233214fp-435, 0x24cedcbff8ad76ab);
}