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make f80 less hacky; lower as u80 on non-x86

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Get rid of `std.math.F80Repr`. Instead of trying to match the memory
layout of f80, we treat it as a value, same as the other floating point
types. The functions `make_f80` and `break_f80` are introduced to
compose an f80 value out of its parts, and the inverse operation.

stage2 LLVM backend: fix pointer to zero length array tripping LLVM
assertion. It now checks for when the element type is a zero-bit type
and lowers such thing the same way that pointers to other zero-bit types
are lowered.

Both stage1 and stage2 LLVM backends are adjusted so that f80 is lowered
as x86_fp80 on x86_64 and i386 architectures, and identical to a u80 on
others. LLVM constants are lowered in a less hacky way now that #10860
is fixed, by using the expression `(exp << 64) | fraction` using llvm
constants.

Sema is improved to handle c_longdouble by recursively handling it
correctly for whatever the float bit width is. In both stage1 and
stage2.
This commit is contained in:
Andrew Kelley
2022-02-10 22:06:43 -07:00
committed by Jakub Konka
parent 1c23321d03
commit a024aff932
10 changed files with 200 additions and 110 deletions
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40
lib/std/math.zig
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@@ -42,19 +42,11 @@ pub const f128_max = @bitCast(f128, @as(u128, 0x7FFEFFFFFFFFFFFFFFFFFFFFFFFFFFFF
pub const f128_epsilon = @bitCast(f128, @as(u128, 0x3F8F0000000000000000000000000000));
pub const f128_toint = 1.0 / f128_epsilon;
pub const F80Repr = if (@import("builtin").cpu.arch.endian() == .Little) extern struct {
fraction: u64 align(@alignOf(f80)),
exp: u16,
} else extern struct {
exp: u16 align(@alignOf(f80)),
fraction: u64,
};
// float.h details
pub const f80_true_min = @ptrCast(*const f80, &F80Repr{ .fraction = 1, .exp = 0 }).*;
pub const f80_min = @ptrCast(*const f80, &F80Repr{ .fraction = 0x8000000000000000, .exp = 1 }).*;
pub const f80_max = @ptrCast(*const f80, &F80Repr{ .fraction = 0xFFFFFFFFFFFFFFFF, .exp = 0x7FFE }).*;
pub const f80_epsilon = @ptrCast(*const f80, &F80Repr{ .fraction = 0x8000000000000000, .exp = 0x3FC0 }).*;
pub const f80_true_min = make_f80(.{ .fraction = 1, .exp = 0 });
pub const f80_min = make_f80(.{ .fraction = 0x8000000000000000, .exp = 1 });
pub const f80_max = make_f80(.{ .fraction = 0xFFFFFFFFFFFFFFFF, .exp = 0x7FFE });
pub const f80_epsilon = make_f80(.{ .fraction = 0x8000000000000000, .exp = 0x3FC0 });
pub const f80_toint = 1.0 / f80_epsilon;
pub const f64_true_min = 4.94065645841246544177e-324;
@@ -104,9 +96,9 @@ pub const qnan_f64 = @bitCast(f64, qnan_u64);
pub const inf_u64 = @as(u64, 0x7FF << 52);
pub const inf_f64 = @bitCast(f64, inf_u64);
pub const inf_f80 = @ptrCast(*const f80, &F80Repr{ .fraction = 0x8000000000000000, .exp = 0x7fff }).*;
pub const nan_f80 = @ptrCast(*const f80, &F80Repr{ .fraction = 0xA000000000000000, .exp = 0x7fff }).*;
pub const qnan_f80 = @ptrCast(*const f80, &F80Repr{ .fraction = 0xC000000000000000, .exp = 0x7fff }).*;
pub const inf_f80 = make_f80(F80{ .fraction = 0x8000000000000000, .exp = 0x7fff });
pub const nan_f80 = make_f80(F80{ .fraction = 0xA000000000000000, .exp = 0x7fff });
pub const qnan_f80 = make_f80(F80{ .fraction = 0xC000000000000000, .exp = 0x7fff });
pub const nan_u128 = @as(u128, 0x7fff0000000000000000000000000001);
pub const nan_f128 = @bitCast(f128, nan_u128);
@@ -1501,3 +1493,21 @@ test "boolMask" {
pub fn comptimeMod(num: anytype, denom: comptime_int) IntFittingRange(0, denom - 1) {
return @intCast(IntFittingRange(0, denom - 1), @mod(num, denom));
}
pub const F80 = struct {
fraction: u64,
exp: u16,
};
pub fn make_f80(repr: F80) f80 {
const int = (@as(u80, repr.exp) << 64) | repr.fraction;
return @bitCast(f80, int);
}
pub fn break_f80(x: f80) F80 {
const int = @bitCast(u80, x);
return .{
.fraction = @truncate(u64, int),
.exp = @truncate(u16, int >> 64),
};
}