higher level representation for initlist #777
Comments
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I want to work for this. Should I start with create a |
Thanks for your interest. We probably want a The first step is to look at the testcases introduced in #764 and propose (with some mocked up CIR example) how that operation would look like - we can discuss it here in this issue. You can optionally post a draft PR with your initial take so you can play with it a bit, but talking about how it might look like is the more important part for now |
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We can create namespace std {
template <class b> class initializer_list {
const b *array_start;
const b *array_end;
};
template <class b> void f(initializer_list<b>) { ; }
void test() { f({1, 2, 3, 4, 5}); }
} // namespace stdC++ AST looks like this, which means we construct %0 = cir.alloca !ty_22std3A3Ainitializer_list3Cint3E22, !cir.ptr<!ty_22std3A3Ainitializer_list3Cint3E22>, ["agg.tmp0"] {alignment = 8 : i64} loc(#loc23)
// allocate tmp array to store initlist.
%1 = cir.alloca !cir.array<!s32i x 5>, !cir.ptr<!cir.array<!s32i x 5>>, ["ref.tmp0"] {alignment = 4 : i64} loc(#loc23)
// use cir.initlist to initialize tmp array.
%2 = cir.const #cir.int<1> : !s32i loc(#loc12)
%3 = cir.const #cir.int<2> : !s32i loc(#loc13)
%4 = cir.const #cir.int<3> : !s32i loc(#loc14)
%5 = cir.const #cir.int<4> : !s32i loc(#loc15)
%6 = cir.const #cir.int<5> : !s32i loc(#loc16)
cir.initlist(%2, %3, %4, %5, %6 : !s32i, !s32i, !s32i, !s32i, !s32i), %1 : <!cir.array<!s32i x 5>> loc(#loc23)
// prepare std::initializer_list with start and end ptr.
%7 = cir.get_member %0[0] {name = "array_start"} : !cir.ptr<!ty_22std3A3Ainitializer_list3Cint3E22> -> !cir.ptr<!cir.ptr<!s32i>> loc(#loc17)
%8 = cir.cast(bitcast, %7 : !cir.ptr<!cir.ptr<!s32i>>), !cir.ptr<!cir.ptr<!cir.array<!s32i x 5>>> loc(#loc17)
cir.store %1, %8 : !cir.ptr<!cir.array<!s32i x 5>>, !cir.ptr<!cir.ptr<!cir.array<!s32i x 5>>> loc(#loc23)
%9 = cir.const #cir.int<5> : !u64i loc(#loc23)
%10 = cir.get_member %0[1] {name = "array_end"} : !cir.ptr<!ty_22std3A3Ainitializer_list3Cint3E22> -> !cir.ptr<!cir.ptr<!s32i>> loc(#loc18)
%11 = cir.ptr_stride(%1 : !cir.ptr<!cir.array<!s32i x 5>>, %9 : !u64i), !cir.ptr<!cir.array<!s32i x 5>> loc(#loc23)
%12 = cir.cast(bitcast, %10 : !cir.ptr<!cir.ptr<!s32i>>), !cir.ptr<!cir.ptr<!cir.array<!s32i x 5>>> loc(#loc18)
cir.store %11, %12 : !cir.ptr<!cir.array<!s32i x 5>>, !cir.ptr<!cir.ptr<!cir.array<!s32i x 5>>> loc(#loc23)
%13 = cir.load %0 : !cir.ptr<!ty_22std3A3Ainitializer_list3Cint3E22>, !ty_22std3A3Ainitializer_list3Cint3E22 loc(#loc8)
cir.call @_ZSt1fIiEvSt16initializer_listIT_E(%13) : (!ty_22std3A3Ainitializer_list3Cint3E22) -> () loc(#loc8) |
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I am not sure whether we should to use a same instruction to initialize array and struct. Because the input and output will be different. array's initialize list must have a common type but struct don't. |
It would be nice in the future to have a
cir.initlistthing - a higher level representation for this (we even have a specialized AST node). Right now it would be really hard to recognize something came from an initializer list if we lower it this early. LoweringPrepare would then lower to what we currently get as of this PR.Originally posted by @bcardosolopes in #764 (review)
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