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stage2: Add support for floats in the C backend (#10059)

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* Implement float type
* Fix int and float undefined value
* Handle NaN constants, preserving bit pattern
This commit is contained in:
Zen1th
2021-11-10 00:56:01 +01:00
committed by GitHub
parent 0d7359ca9b
commit 6869bc9ff8
2 changed files with 63 additions and 7 deletions
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57
src/codegen/c.zig
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@@ -219,11 +219,36 @@ pub const DeclGen = struct {
val: Value,
) error{ OutOfMemory, AnalysisFail }!void {
if (val.isUndef()) {
// This should lower to 0xaa bytes in safe modes, and for unsafe modes should
// lower to leaving variables uninitialized (that might need to be implemented
// outside of this function).
return writer.writeAll("{}");
//return dg.fail("TODO: C backend: implement renderValue undef", .{});
switch (ty.zigTypeTag()) {
// Using '{}' for integer and floats seemed to error C compilers (both GCC and Clang)
// with 'error: expected expression' (including when built with 'zig cc')
.Int => {
const c_bits = toCIntBits(ty.intInfo(dg.module.getTarget()).bits) orelse
return dg.fail("TODO: C backend: implement integer types larger than 128 bits", .{});
switch (c_bits) {
8 => return writer.writeAll("0xaaU"),
16 => return writer.writeAll("0xaaaaU"),
32 => return writer.writeAll("0xaaaaaaaaU"),
64 => return writer.writeAll("0xaaaaaaaaaaaaaaaaUL"),
128 => return writer.writeAll("0xaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaULL"),
else => unreachable,
}
},
.Float => {
switch (ty.floatBits(dg.module.getTarget())) {
32 => return writer.writeAll("zig_bitcast_f32_u32(0xaaaaaaaa)"),
64 => return writer.writeAll("zig_bitcast_f64_u64(0xaaaaaaaaaaaaaaaa)"),
else => return dg.fail("TODO float types > 64 bits are not support in renderValue() as of now", .{}),
}
},
else => {
// This should lower to 0xaa bytes in safe modes, and for unsafe modes should
// lower to leaving variables uninitialized (that might need to be implemented
// outside of this function).
return writer.writeAll("{}");
},
}
}
switch (ty.zigTypeTag()) {
.Int => {
@@ -233,7 +258,16 @@ pub const DeclGen = struct {
},
.Float => {
if (ty.floatBits(dg.module.getTarget()) <= 64) {
return writer.print("{x}", .{val.toFloat(f64)});
if (std.math.isNan(val.toFloat(f64)) or std.math.isInf(val.toFloat(f64))) {
// just generate a bit cast (exactly like we do in airBitcast)
switch (ty.tag()) {
.f32 => return writer.print("zig_bitcast_f32_u32(0x{x})", .{@bitCast(u32, val.toFloat(f32))}),
.f64 => return writer.print("zig_bitcast_f64_u64(0x{x})", .{@bitCast(u64, val.toFloat(f64))}),
else => return dg.fail("TODO float types > 64 bits are not support in renderValue() as of now", .{}),
}
} else {
return writer.print("{x}", .{val.toFloat(f64)});
}
}
return dg.fail("TODO: C backend: implement lowering large float values", .{});
},
@@ -521,7 +555,16 @@ pub const DeclGen = struct {
}
},
.Float => return dg.fail("TODO: C backend: implement type Float", .{}),
.Float => {
switch (t.tag()) {
.f32 => try w.writeAll("float"),
.f64 => try w.writeAll("double"),
.c_longdouble => try w.writeAll("long double"),
.f16 => return dg.fail("TODO: C backend: implement float type f16", .{}),
.f128 => return dg.fail("TODO: C backend: implement float type f128", .{}),
else => unreachable,
}
},
.Pointer => {
if (t.isSlice()) {

13
src/link/C/zig.h
View File

@@ -123,6 +123,7 @@
#include <stdint.h>
#include <stddef.h>
#include <limits.h>
#define int128_t __int128
#define uint128_t unsigned __int128
ZIG_EXTERN_C void *memcpy (void *ZIG_RESTRICT, const void *ZIG_RESTRICT, size_t);
@@ -356,6 +357,18 @@ static inline long long zig_subw_longlong(long long lhs, long long rhs, long lon
return (long long)(((unsigned long long)lhs) - ((unsigned long long)rhs));
}
static inline float zig_bitcast_f32_u32(uint32_t arg) {
float dest;
memcpy(&dest, &arg, sizeof dest);
return dest;
}
static inline float zig_bitcast_f64_u64(uint64_t arg) {
double dest;
memcpy(&dest, &arg, sizeof dest);
return dest;
}
#define zig_add_sat_u(ZT, T) static inline T zig_adds_##ZT(T x, T y, T max) { \
return (x > max - y) ? max : x + y; \
}