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| author | Kostis Sagonas <[email protected]> | 2014-03-26 23:51:05 +0100 |
|---|---|---|
| committer | Kostis Sagonas <[email protected]> | 2014-03-26 23:51:05 +0100 |
| commit | 32eae452dbd6da109914af3a9003d9bbcb696d42 (patch) | |
| tree | 4101250db704e0d2b02e87c93f9daee0a081a211 | |
| parent | c5e3c774bd12cc15a04dd9880cad6eb66d2541be (diff) | |
| download | otp-32eae452dbd6da109914af3a9003d9bbcb696d42.tar.gz otp-32eae452dbd6da109914af3a9003d9bbcb696d42.tar.bz2 otp-32eae452dbd6da109914af3a9003d9bbcb696d42.zip | |
Change the subtag used for maps from 0xB to 0xF
The subtag chosen for maps breaks crucial assumptions in other parts of
the system, in particular the native code generation scheme used in the
HiPE compiler. Therefore it is better to use 'the other' unused subtag.
The main change here is the use of 0xF subtag for maps instead of 0xB.
The rest of the differences are changes to and additions of comments.
One more comment from my part.
I noticed that the file contains the following two lines:
The comment of the second line is most certainly a copy and paste error
and should be appropriately fixed by the OTP developers. More importantly,
it would be great if that subtag (0x7) turned out to be unused and could
be used for maps instead of the 0xF one. This might turn out very handy
in the future. I can elaborate on this, if needed.
| -rw-r--r-- | erts/emulator/beam/erl_term.h | 9 |
1 files changed, 5 insertions, 4 deletions
diff --git a/erts/emulator/beam/erl_term.h b/erts/emulator/beam/erl_term.h index f10a3a9d38..982e63ee31 100644 --- a/erts/emulator/beam/erl_term.h +++ b/erts/emulator/beam/erl_term.h @@ -112,11 +112,11 @@ struct erl_node_; /* Declared in erl_node_tables.h */ * 1000 REFC_BINARY | | * 1001 HEAP_BINARY | BINARIES | * 1010 SUB_BINARY | | - * 1011 Not used + * 1011 Not used; see comment below * 1100 EXTERNAL_PID | | * 1101 EXTERNAL_PORT | EXTERNAL THINGS | * 1110 EXTERNAL_REF | | - * 1111 Not used + * 1111 MAP * * COMMENTS: * @@ -140,10 +140,11 @@ struct erl_node_; /* Declared in erl_node_tables.h */ #define REFC_BINARY_SUBTAG (0x8 << _TAG_PRIMARY_SIZE) /* BINARY */ #define HEAP_BINARY_SUBTAG (0x9 << _TAG_PRIMARY_SIZE) /* BINARY */ #define SUB_BINARY_SUBTAG (0xA << _TAG_PRIMARY_SIZE) /* BINARY */ -#define MAP_SUBTAG (0xB << _TAG_PRIMARY_SIZE) /* MAP */ +/* _BINARY_XXX_MASK depends on 0xB being unused */ #define EXTERNAL_PID_SUBTAG (0xC << _TAG_PRIMARY_SIZE) /* EXTERNAL_PID */ #define EXTERNAL_PORT_SUBTAG (0xD << _TAG_PRIMARY_SIZE) /* EXTERNAL_PORT */ #define EXTERNAL_REF_SUBTAG (0xE << _TAG_PRIMARY_SIZE) /* EXTERNAL_REF */ +#define MAP_SUBTAG (0xF << _TAG_PRIMARY_SIZE) /* MAP */ #define _TAG_HEADER_ARITYVAL (TAG_PRIMARY_HEADER|ARITYVAL_SUBTAG) @@ -156,11 +157,11 @@ struct erl_node_; /* Declared in erl_node_tables.h */ #define _TAG_HEADER_REFC_BIN (TAG_PRIMARY_HEADER|REFC_BINARY_SUBTAG) #define _TAG_HEADER_HEAP_BIN (TAG_PRIMARY_HEADER|HEAP_BINARY_SUBTAG) #define _TAG_HEADER_SUB_BIN (TAG_PRIMARY_HEADER|SUB_BINARY_SUBTAG) -#define _TAG_HEADER_MAP (TAG_PRIMARY_HEADER|MAP_SUBTAG) #define _TAG_HEADER_EXTERNAL_PID (TAG_PRIMARY_HEADER|EXTERNAL_PID_SUBTAG) #define _TAG_HEADER_EXTERNAL_PORT (TAG_PRIMARY_HEADER|EXTERNAL_PORT_SUBTAG) #define _TAG_HEADER_EXTERNAL_REF (TAG_PRIMARY_HEADER|EXTERNAL_REF_SUBTAG) #define _TAG_HEADER_BIN_MATCHSTATE (TAG_PRIMARY_HEADER|BIN_MATCHSTATE_SUBTAG) +#define _TAG_HEADER_MAP (TAG_PRIMARY_HEADER|MAP_SUBTAG) #define _TAG_HEADER_MASK 0x3F |