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From: Pierre-Marie de Rodat <pmderodat@gcc.gnu.org> To: gcc-cvs@gcc.gnu.org Subject: [gcc r12-1638] [Ada] Minor comment cleanups Date: Fri, 18 Jun 2021 08:39:57 +0000 (GMT) [thread overview] Message-ID: <20210618083957.A0E5139B4415@sourceware.org> (raw) https://gcc.gnu.org/g:161e220201436a641df5f5d86fdbaebb599302fc commit r12-1638-g161e220201436a641df5f5d86fdbaebb599302fc Author: Bob Duff <duff@adacore.com> Date: Tue Mar 23 16:00:03 2021 -0400 [Ada] Minor comment cleanups gcc/ada/ * gen_il-gen.adb: Improve comments. * snames.ads-tmpl (Convention_Id): Remove "-- Plenty of space for expansion", because that's irrelevant now that we are no longer laying out node fields by hand. Diff: --- gcc/ada/gen_il-gen.adb | 37 +++++++++++++++++++++++++------------ gcc/ada/snames.ads-tmpl | 1 - 2 files changed, 25 insertions(+), 13 deletions(-) diff --git a/gcc/ada/gen_il-gen.adb b/gcc/ada/gen_il-gen.adb index 61d464c9ce0..7ef285ee458 100644 --- a/gcc/ada/gen_il-gen.adb +++ b/gcc/ada/gen_il-gen.adb @@ -837,20 +837,24 @@ package body Gen_IL.Gen is when Node_Kind_Type | Entity_Kind_Type | Convention_Id => 8, - when Mechanism_Type - | List_Id - | Elist_Id - | Name_Id - | String_Id - | Uint - | Ureal - | Source_Ptr - | Union_Id - | Node_Id - | Node_Or_Entity_Type => 32, + when Mechanism_Type + | List_Id + | Elist_Id + | Name_Id + | String_Id + | Uint + | Ureal + | Source_Ptr + | Union_Id + | Node_Id + | Node_Or_Entity_Type => 32, when Between_Special_And_Abstract_Node_Types => -- can't happen Bit_Offset'Last); + -- Size in bits of a a field of type T. It must be a power of 2, and + -- must match the size of the type in GNAT, which sometimes requires + -- a Size clause in GNAT. + -- -- Note that this is not the same as Type_Bit_Size of the field's -- type. For one thing, Type_Bit_Size only covers concrete node and -- entity types, which does not include most of the above. For @@ -1012,11 +1016,20 @@ package body Gen_IL.Gen is end loop; -- Sort All_Fields based on how many concrete types have the field. + -- This is for efficiency; we want to choose the offsets of the most + -- common fields first, so they get low numbers. Sorting.Sort (All_Fields); -- Go through all the fields, and choose the lowest offset that is - -- free in all types that have the field. + -- free in all types that have the field. This is basically a + -- graph-coloring algorithm on the interference graph. The + -- interference graph is an undirected graph with the fields being + -- nodes (not nodes in the compiler!) in the graph, and an edge + -- between a pair of fields if they appear in the same node in the + -- compiler. The "colors" are fields offsets, except that a + -- complication compared to standard graph coloring is that fields + -- are different sizes. for F of All_Fields loop Field_Table (F).Offset := Choose_Offset (F); diff --git a/gcc/ada/snames.ads-tmpl b/gcc/ada/snames.ads-tmpl index e5a019fc087..2611541dd78 100644 --- a/gcc/ada/snames.ads-tmpl +++ b/gcc/ada/snames.ads-tmpl @@ -1700,7 +1700,6 @@ package Snames is -- in Sem_Prag. for Convention_Id'Size use 8; - -- Plenty of space for expansion subtype Convention_C_Family is Convention_Id range Convention_C .. Convention_CPP;
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