Commit c9ecf7b920f1e5b7aa2366e83f722de46813ace3 | zig

author	Cody Tapscott <topolarity@tapscott.me> 2022-10-09 13:42:39-07:00
committer	Cody Tapscott <topolarity@tapscott.me> 2022-10-09 13:42:39-07:00
log	c9ecf7b920f1e5b7aa2366e83f722de46813ace3
tree	86586779a6be2ee831181859c19bfcd31ea18002
parent	05915b85dd3c00c40bf6645e0f09157be04dc829

compiler_rt: Fix `extendf_f80` bug

Zig should probably perform this cast automatically (w/ safety).
Integer shifts are a real pain otherwise.

Adds some test coverage, too.

3 files changed, 52 insertions(+), 2 deletions(-)

lib
- compiler_rt

lib/compiler_rt/extenddfxf2.zig+1-1

...	...	@@ -7,6 +7,6 @@ comptime {
7	7	@export(__extenddfxf2, .{ .name = "__extenddfxf2", .linkage = common.linkage });
8	8	}
9	9
10		fn __extenddfxf2(a: f64) callconv(.C) f80 {
	10	pub fn __extenddfxf2(a: f64) callconv(.C) f80 {
11	11	return extend_f80(f64, @bitCast(u64, a));
12	12	}

lib/compiler_rt/extendf.zig+3-1

...	...	@@ -92,6 +92,8 @@ pub inline fn extend_f80(comptime src_t: type, a: std.meta.Int(.unsigned, @typeI
92	92	const src_qnan = 1 << (src_sig_bits - 1);
93	93	const src_nan_code = src_qnan - 1;
94	94
	95	const SrcShift = std.math.Log2Int(src_rep_t);
	96
95	97	var dst: std.math.F80 = undefined;
96	98
97	99	// Break a into a sign and representation of the absolute value
...	...	@@ -124,7 +126,7 @@ pub inline fn extend_f80(comptime src_t: type, a: std.meta.Int(.unsigned, @typeI
124	126
125	127	dst.fraction = @as(u64, a_abs) << @intCast(u6, dst_sig_bits - src_sig_bits + scale);
126	128	dst.fraction \|= dst_int_bit; // bit 64 is always set for normal numbers
127		dst.exp = @truncate(u16, a_abs >> @intCast(u4, src_sig_bits - scale));
	129	dst.exp = @truncate(u16, a_abs >> @intCast(SrcShift, src_sig_bits - scale));
128	130	dst.exp ^= 1;
129	131	dst.exp \|= dst_exp_bias - src_exp_bias - scale + 1;
130	132	} else {

lib/compiler_rt/extendf_test.zig+48

...	...	@@ -1,10 +1,27 @@
	1	const std = @import("std");
	2	const math = std.math;
1	3	const builtin = @import("builtin");
2	4	const __extendhfsf2 = @import("extendhfsf2.zig").__extendhfsf2;
3	5	const __extendhftf2 = @import("extendhftf2.zig").__extendhftf2;
4	6	const __extendsftf2 = @import("extendsftf2.zig").__extendsftf2;
5	7	const __extenddftf2 = @import("extenddftf2.zig").__extenddftf2;
	8	const __extenddfxf2 = @import("extenddfxf2.zig").__extenddfxf2;
6	9	const F16T = @import("./common.zig").F16T;
7	10
	11	fn test__extenddfxf2(a: f64, expected: u80) !void {
	12	const x = __extenddfxf2(a);
	13
	14	const rep = @bitCast(u80, x);
	15	if (rep == expected)
	16	return;
	17
	18	// test other possible NaN representation(signal NaN)
	19	if (math.isNan(@bitCast(f80, expected)) and math.isNan(x))
	20	return;
	21
	22	@panic("__extenddfxf2 test failure");
	23	}
	24
8	25	fn test__extenddftf2(a: f64, expected_hi: u64, expected_lo: u64) !void {
9	26	const x = __extenddftf2(a);
10	27
...	...	@@ -65,6 +82,33 @@ fn test__extendsftf2(a: f32, expected_hi: u64, expected_lo: u64) !void {
65	82	return error.TestFailure;
66	83	}
67	84
	85	test "extenddfxf2" {
	86	// qNaN
	87	try test__extenddfxf2(makeQNaN64(), 0x7fffc000000000000000);
	88
	89	// NaN
	90	try test__extenddfxf2(makeNaN64(0x7100000000000), 0x7fffe080000000000000);
	91	// This is bad?
	92
	93	// inf
	94	try test__extenddfxf2(makeInf64(), 0x7fff8000000000000000);
	95
	96	// zero
	97	try test__extenddfxf2(0.0, 0x0);
	98
	99	try test__extenddfxf2(0x0.a3456789abcdefp+6, 0x4004a3456789abcdf000);
	100
	101	try test__extenddfxf2(0x0.edcba987654321fp-8, 0x3ff6edcba98765432000);
	102
	103	try test__extenddfxf2(0x0.a3456789abcdefp+46, 0x402ca3456789abcdf000);
	104
	105	try test__extenddfxf2(0x0.edcba987654321fp-44, 0x3fd2edcba98765432000);
	106
	107	// subnormal
	108	try test__extenddfxf2(0x1.8000000000001p-1022, 0x3c01c000000000000800);
	109	try test__extenddfxf2(0x1.8000000000002p-1023, 0x3c00c000000000001000);
	110	}
	111
68	112	test "extenddftf2" {
69	113	// qNaN
70	114	try test__extenddftf2(makeQNaN64(), 0x7fff800000000000, 0x0);
...	...	@@ -85,6 +129,10 @@ test "extenddftf2" {
85	129	try test__extenddftf2(0x1.23456789abcdefp+45, 0x402c23456789abcd, 0xf000000000000000);
86	130
87	131	try test__extenddftf2(0x1.edcba987654321fp-45, 0x3fd2edcba9876543, 0x2000000000000000);
	132
	133	// subnormal
	134	try test__extenddftf2(0x1.8p-1022, 0x3c01800000000000, 0x0);
	135	try test__extenddftf2(0x1.8p-1023, 0x3c00800000000000, 0x0);
88	136	}
89	137
90	138	test "extendhfsf2" {