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Merge pull request #4797 from laytan/improve-abs-of-float
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improve abs() on floats for more correct and faster results
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@gingerBill
gingerBill authored Feb 8, 2025
2 parents cf326df + 5defddf commit fbee045
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Showing 3 changed files with 198 additions and 2 deletions.
7 changes: 5 additions & 2 deletions src/check_builtin.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -3488,9 +3488,12 @@ gb_internal bool check_builtin_procedure(CheckerContext *c, Operand *operand, As
case ExactValue_Integer:
mp_abs(&operand->value.value_integer, &operand->value.value_integer);
break;
case ExactValue_Float:
operand->value.value_float = gb_abs(operand->value.value_float);
case ExactValue_Float: {
u64 abs = bit_cast<u64>(operand->value.value_float);
abs &= 0x7FFFFFFFFFFFFFFF;
operand->value.value_float = bit_cast<f64>(abs);
break;
}
case ExactValue_Complex: {
f64 r = operand->value.value_complex->real;
f64 i = operand->value.value_complex->imag;
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25 changes: 25 additions & 0 deletions src/llvm_backend_proc.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2174,7 +2174,32 @@ gb_internal lbValue lb_build_builtin_proc(lbProcedure *p, Ast *expr, TypeAndValu
case 128: return lb_emit_runtime_call(p, "abs_complex128", args);
}
GB_PANIC("Unknown complex type");
} else if (is_type_float(t)) {
bool little = is_type_endian_little(t) || (is_type_endian_platform(t) && build_context.endian_kind == TargetEndian_Little);
Type *t_unsigned = nullptr;
lbValue mask = {0};
switch (type_size_of(t)) {
case 2:
t_unsigned = t_u16;
mask = lb_const_int(p->module, t_unsigned, little ? 0x7FFF : 0xFF7F);
break;
case 4:
t_unsigned = t_u32;
mask = lb_const_int(p->module, t_unsigned, little ? 0x7FFFFFFF : 0xFFFFFF7F);
break;
case 8:
t_unsigned = t_u64;
mask = lb_const_int(p->module, t_unsigned, little ? 0x7FFFFFFFFFFFFFFF : 0xFFFFFFFFFFFFFF7F);
break;
default:
GB_PANIC("abs: unhandled float size");
}

lbValue as_unsigned = lb_emit_transmute(p, x, t_unsigned);
lbValue abs = lb_emit_arith(p, Token_And, as_unsigned, mask, t_unsigned);
return lb_emit_transmute(p, abs, t);
}

lbValue zero = lb_const_nil(p->module, t);
lbValue cond = lb_emit_comp(p, Token_Lt, x, zero);
lbValue neg = lb_emit_unary_arith(p, Token_Sub, x, t);
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168 changes: 168 additions & 0 deletions tests/internal/test_abs.odin
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@@ -0,0 +1,168 @@
package test_internal

import "core:testing"

@(private="file")
not_const :: proc(v: $T) -> T { return v }

@(test)
abs_f16_const :: proc(t: ^testing.T) {
// Constant f16
testing.expect_value(t, abs(f16(0.)), 0.)
testing.expect_value(t, abs(f16(-0.)), 0.)
testing.expect_value(t, abs(f16(-1.)), 1.)
testing.expect_value(t, abs(min(f16)), max(f16))
testing.expect_value(t, abs(max(f16)), max(f16))
testing.expect_value(t, abs(f16(-.12)), .12)

// Constant f16le
testing.expect_value(t, abs(f16le(0.)), 0.)
testing.expect_value(t, abs(f16le(-0.)), 0.)
testing.expect_value(t, abs(f16le(-1.)), 1.)
testing.expect_value(t, abs(min(f16le)), max(f16le))
testing.expect_value(t, abs(max(f16le)), max(f16le))
testing.expect_value(t, abs(f16le(-.12)), .12)

// Constant f16be
testing.expect_value(t, abs(f16be(0.)), 0.)
testing.expect_value(t, abs(f16be(-0.)), 0.)
testing.expect_value(t, abs(f16be(-1.)), 1.)
testing.expect_value(t, abs(min(f16be)), max(f16be))
testing.expect_value(t, abs(max(f16be)), max(f16be))
testing.expect_value(t, abs(f16be(-.12)), .12)
}

@(test)
abs_f16_variable :: proc(t: ^testing.T) {
// Variable f16
testing.expect_value(t, abs(not_const(f16(0.))), 0.)
testing.expect_value(t, abs(not_const(f16(-0.))), 0.)
testing.expect_value(t, abs(not_const(f16(-1.))), 1.)
testing.expect_value(t, abs(not_const(min(f16))), max(f16))
testing.expect_value(t, abs(not_const(max(f16))), max(f16))
testing.expect_value(t, abs(not_const(f16(-.12))), .12)

// Variable f16le
testing.expect_value(t, abs(not_const(f16le(0.))), 0.)
testing.expect_value(t, abs(not_const(f16le(-0.))), 0.)
testing.expect_value(t, abs(not_const(f16le(-1.))), 1.)
testing.expect_value(t, abs(not_const(min(f16le))), max(f16le))
testing.expect_value(t, abs(not_const(max(f16le))), max(f16le))
testing.expect_value(t, abs(not_const(f16le(-.12))), .12)

// Variable f16be
testing.expect_value(t, abs(not_const(f16be(0.))), 0.)
testing.expect_value(t, abs(not_const(f16be(-0.))), 0.)
testing.expect_value(t, abs(not_const(f16be(-1.))), 1.)
testing.expect_value(t, abs(not_const(min(f16be))), max(f16be))
testing.expect_value(t, abs(not_const(max(f16be))), max(f16be))
testing.expect_value(t, abs(not_const(f16be(-.12))), .12)
}

@(test)
abs_f32_const :: proc(t: ^testing.T) {
// Constant f32
testing.expect_value(t, abs(f32(0.)), 0.)
testing.expect_value(t, abs(f32(-0.)), 0.)
testing.expect_value(t, abs(f32(-1.)), 1.)
testing.expect_value(t, abs(min(f32)), max(f32))
testing.expect_value(t, abs(max(f32)), max(f32))
testing.expect_value(t, abs(f32(-.12345)), .12345)

// Constant f32le
testing.expect_value(t, abs(f32le(0.)), 0.)
testing.expect_value(t, abs(f32le(-0.)), 0.)
testing.expect_value(t, abs(f32le(-1.)), 1.)
testing.expect_value(t, abs(min(f32le)), max(f32le))
testing.expect_value(t, abs(max(f32le)), max(f32le))
testing.expect_value(t, abs(f32le(-.12345)), .12345)

// Constant f32be
testing.expect_value(t, abs(f32be(0.)), 0.)
testing.expect_value(t, abs(f32be(-0.)), 0.)
testing.expect_value(t, abs(f32be(-1.)), 1.)
testing.expect_value(t, abs(min(f32be)), max(f32be))
testing.expect_value(t, abs(max(f32be)), max(f32be))
testing.expect_value(t, abs(f32be(-.12345)), .12345)
}

@(test)
abs_f32_variable :: proc(t: ^testing.T) {
// Variable f32
testing.expect_value(t, abs(not_const(f32(0.))), 0.)
testing.expect_value(t, abs(not_const(f32(-0.))), 0.)
testing.expect_value(t, abs(not_const(f32(-1.))), 1.)
testing.expect_value(t, abs(not_const(min(f32))), max(f32))
testing.expect_value(t, abs(not_const(max(f32))), max(f32))
testing.expect_value(t, abs(not_const(f32(-.12345))), .12345)

// Variable f32le
testing.expect_value(t, abs(not_const(f32le(0.))), 0.)
testing.expect_value(t, abs(not_const(f32le(-0.))), 0.)
testing.expect_value(t, abs(not_const(f32le(-1.))), 1.)
testing.expect_value(t, abs(not_const(min(f32le))), max(f32le))
testing.expect_value(t, abs(not_const(max(f32le))), max(f32le))
testing.expect_value(t, abs(not_const(f32le(-.12345))), .12345)

// Variable f32be
testing.expect_value(t, abs(not_const(f32be(0.))), 0.)
testing.expect_value(t, abs(not_const(f32be(-0.))), 0.)
testing.expect_value(t, abs(not_const(f32be(-1.))), 1.)
testing.expect_value(t, abs(not_const(min(f32be))), max(f32be))
testing.expect_value(t, abs(not_const(max(f32be))), max(f32be))
testing.expect_value(t, abs(not_const(f32be(-.12345))), .12345)
}

@(test)
abs_f64_const :: proc(t: ^testing.T) {
// Constant f64
testing.expect_value(t, abs(f64(0.)), 0.)
testing.expect_value(t, abs(f64(-0.)), 0.)
testing.expect_value(t, abs(f64(-1.)), 1.)
testing.expect_value(t, abs(min(f64)), max(f64))
testing.expect_value(t, abs(max(f64)), max(f64))
testing.expect_value(t, abs(f64(-.12345)), .12345)

// Constant f64le
testing.expect_value(t, abs(f64le(0.)), 0.)
testing.expect_value(t, abs(f64le(-0.)), 0.)
testing.expect_value(t, abs(f64le(-1.)), 1.)
testing.expect_value(t, abs(min(f64le)), max(f64le))
testing.expect_value(t, abs(max(f64le)), max(f64le))
testing.expect_value(t, abs(f64le(-.12345)), .12345)

// Constant f64be
testing.expect_value(t, abs(f64be(0.)), 0.)
testing.expect_value(t, abs(f64be(-0.)), 0.)
testing.expect_value(t, abs(f64be(-1.)), 1.)
testing.expect_value(t, abs(min(f64be)), max(f64be))
testing.expect_value(t, abs(max(f64be)), max(f64be))
testing.expect_value(t, abs(f64be(-.12345)), .12345)
}

@(test)
abs_f64_variable :: proc(t: ^testing.T) {
// Variable f64
testing.expect_value(t, abs(not_const(f64(0.))), 0.)
testing.expect_value(t, abs(not_const(f64(-0.))), 0.)
testing.expect_value(t, abs(not_const(f64(-1.))), 1.)
testing.expect_value(t, abs(not_const(min(f64))), max(f64))
testing.expect_value(t, abs(not_const(max(f64))), max(f64))
testing.expect_value(t, abs(not_const(f64(-.12345))), .12345)

// Variable f64le
testing.expect_value(t, abs(not_const(f64le(0.))), 0.)
testing.expect_value(t, abs(not_const(f64le(-0.))), 0.)
testing.expect_value(t, abs(not_const(f64le(-1.))), 1.)
testing.expect_value(t, abs(not_const(min(f64le))), max(f64le))
testing.expect_value(t, abs(not_const(max(f64le))), max(f64le))
testing.expect_value(t, abs(not_const(f64le(-.12345))), .12345)

// Variable f64be
testing.expect_value(t, abs(not_const(f64be(0.))), 0.)
testing.expect_value(t, abs(not_const(f64be(-0.))), 0.)
testing.expect_value(t, abs(not_const(f64be(-1.))), 1.)
testing.expect_value(t, abs(not_const(min(f64be))), max(f64be))
testing.expect_value(t, abs(not_const(max(f64be))), max(f64be))
testing.expect_value(t, abs(not_const(f64be(-.12345))), .12345)
}

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