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less branches for division + fix divide by zeros (#2585)
Slight change to float divide operations (again). Now it only turns into inverse multiplication if the float is a power of 2 (positive or negative). Non-zero immediate divisors will be compiled as regular float divisions but will forgo the extra branches and checks for divide by zero. Also fixes #2584
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0d3e272876
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2feb231105
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@ -41,6 +41,7 @@
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#include "Object.h"
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#include <cinttypes>
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#include <cstring>
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#include "common/util/FileUtil.h"
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#include "common/util/print_float.h"
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@ -207,6 +208,19 @@ Object build_list(std::vector<Object>&& objects) {
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return result;
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}
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/*!
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* Is this a float object that's a power of two?
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* NOTE: assumes 64-bit float.
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*/
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bool Object::is_power_of_2_float() const {
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FloatType val = as_float();
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u64 val_i = -1;
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memcpy(&val_i, &val, sizeof(val));
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u64 mantissa = val_i & ((1LL << 52) - 1);
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u64 exponent = (val_i >> 52) & ((1LL << 11) - 1);
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return mantissa == 0 && exponent != 0 && exponent != ((1LL << 11) - 1);
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}
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/*!
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* Compare two objects for equality.
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* Does "expensive" checking.
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@ -309,6 +309,8 @@ class Object {
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bool is_macro() const { return type == ObjectType::MACRO; }
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bool is_string_hash_table() const { return type == ObjectType::STRING_HASH_TABLE; }
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bool is_power_of_2_float() const;
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bool operator==(const Object& other) const;
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bool operator!=(const Object& other) const { return !((*this) == other); }
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};
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@ -339,7 +339,8 @@ class Compiler {
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const TypeSpec& result_type,
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RegVal* a,
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RegVal* b,
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Env* env);
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Env* env,
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bool imm_divisor);
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Val* compile_format_string(const goos::Object& form,
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Env* env,
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@ -373,11 +373,12 @@ Val* Compiler::compile_floating_point_division(const goos::Object& form,
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const TypeSpec& result_type,
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RegVal* a,
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RegVal* b,
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Env* env) {
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Env* env,
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bool imm_divisor) {
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constexpr bool use_accurate = true;
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auto result = env->make_fpr(result_type);
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if (use_accurate) {
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if (use_accurate && !imm_divisor) {
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auto fenv = env->function_env();
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auto end_label = fenv->alloc_unnamed_label();
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end_label->func = fenv;
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@ -404,8 +405,9 @@ Val* Compiler::compile_floating_point_division(const goos::Object& form,
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branch_ir_ref->mark_as_resolved();
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branch_ir_ref->label.idx = fenv->code().size();
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// code for dividing by zero
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auto flt_max = compile_integer(0x7f7fffff, env)->to_gpr(form, env);
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auto mask = compile_integer(0xf0000000, env)->to_gpr(form, env);
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auto mask = compile_integer(0x80000000, env)->to_gpr(form, env);
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auto temp_int = env->make_gpr(result_type);
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env->emit_ir<IR_RegSet>(form, temp_int, a);
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env->emit_ir<IR_IntegerMath>(form, IntegerMathKind::AND_64, temp_int, mask);
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@ -482,17 +484,19 @@ Val* Compiler::compile_div(const goos::Object& form, const goos::Object& rest, E
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case MATH_FLOAT: {
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const auto& divisor = args.unnamed.at(1);
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// in original GOAL, immediate divisions were turned into inverse multiplications
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if (divisor.is_float() && !divisor.is_float(0)) {
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if (divisor.is_float() && !divisor.is_float(0) && divisor.is_power_of_2_float()) {
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// TODO eventually this should be smarter somehow
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auto as_inverse_mult =
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pretty_print::build_list({pretty_print::to_symbol("*"), args.unnamed.at(0),
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goos::Object::make_float(1.0 / divisor.as_float())});
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return compile_mul(as_inverse_mult, as_inverse_mult.as_pair()->cdr, env);
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return compile_mul(
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form,
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pretty_print::build_list(
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{goos::Object::make_float(1.0 / divisor.as_float()), args.unnamed.at(0)}),
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env);
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} else {
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auto a = first_val->to_fpr(form, env);
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auto b = to_math_type(form, compile_error_guard(divisor, env), math_type, env)
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->to_fpr(form, env);
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return compile_floating_point_division(form, first_type, a, b, env);
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return compile_floating_point_division(form, first_type, a, b, env,
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divisor.is_float() && !divisor.is_float(0));
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}
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}
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