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Tiny improvements in codegen in C backend #7337

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merged 4 commits into from
Feb 11, 2023
Merged

Tiny improvements in codegen in C backend #7337

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302211c
Tiny improvements in codegen in C backend
steven-johnson Feb 10, 2023
d467ff0
Also avoid extra intermediates for typed nullptr
steven-johnson Feb 10, 2023
3c74867
Also use std::isnan() and std::isinf()
steven-johnson Feb 10, 2023
72720c9
Update CodeGen_C.cpp
steven-johnson Feb 10, 2023
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52 changes: 29 additions & 23 deletions src/CodeGen_C.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1384,7 +1384,19 @@ string CodeGen_C::print_reinterpret(Type type, const Expr &e) {
} else {
oss << "reinterpret<" << print_type(type) << ">";
}
oss << "(" << print_expr(e) << ")";
// If we are generating a typed nullptr, just emit that as a literal, with no intermediate,
// to avoid ugly code like
//
// uint64_t _32 = (uint64_t)(0ull);
// auto *_33 = (void *)(_32);
//
// and instead just do
// auto *_33 = (void *)(nullptr);
if (type.is_handle() && is_const_zero(e)) {
oss << "(nullptr)";
} else {
oss << "(" << print_expr(e) << ")";
}
return oss.str();
}

Expand Down Expand Up @@ -2201,6 +2213,10 @@ string CodeGen_C::print_expr(const Expr &e) {

string CodeGen_C::print_cast_expr(const Type &t, const Expr &e) {
string value = print_expr(e);
if (e.type() == t) {
// This is uncommon but does happen occasionally
return value;
}
string type = print_type(t);
if (t.is_vector() &&
t.lanes() == e.type().lanes() &&
Expand Down Expand Up @@ -2405,12 +2421,16 @@ void CodeGen_C::visit(const IntImm *op) {
}

void CodeGen_C::visit(const UIntImm *op) {
static const char *const suffixes[3] = {
"ull", // PlainC
"ul", // OpenCL
"", // HLSL
};
print_assignment(op->type, "(" + print_type(op->type) + ")(" + std::to_string(op->value) + suffixes[(int)integer_suffix_style] + ")");
if (op->type == UInt(1)) {
id = op->value ? "true" : "false";
} else {
static const char *const suffixes[3] = {
"ull", // PlainC
"ul", // OpenCL
"", // HLSL
};
print_assignment(op->type, "(" + print_type(op->type) + ")(" + std::to_string(op->value) + suffixes[(int)integer_suffix_style] + ")");
}
}

void CodeGen_C::visit(const StringImm *op) {
Expand All @@ -2419,24 +2439,10 @@ void CodeGen_C::visit(const StringImm *op) {
id = oss.str();
}

// NaN is the only float/double for which this is true... and
// surprisingly, there doesn't seem to be a portable isnan function
// (dsharlet).
template<typename T>
static bool isnan(T x) {
return x != x;
}

template<typename T>
static bool isinf(T x) {
return std::numeric_limits<T>::has_infinity && (x == std::numeric_limits<T>::infinity() ||
x == -std::numeric_limits<T>::infinity());
}

void CodeGen_C::visit(const FloatImm *op) {
if (isnan(op->value)) {
if (std::isnan(op->value)) {
id = "nan_f32()";
} else if (isinf(op->value)) {
} else if (std::isinf(op->value)) {
if (op->value > 0) {
id = "inf_f32()";
} else {
Expand Down