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| author | Siddhesh Poyarekar <siddhesh@sourceware.org> | 2018-06-27 05:28:06 +0000 |
|---|---|---|
| committer | Siddhesh Poyarekar <siddhesh@gcc.gnu.org> | 2018-06-27 05:28:06 +0000 |
| commit | 643ef9571905ce704dc68ef27708e83a2a242355 (patch) | |
| tree | 893e466023b775720d6b7c56c98cc714013cc9da /gcc | |
| parent | 307193b82cecb8ab79cf8880d642e1a3acb9c9f6 (diff) | |
| download | gcc-643ef9571905ce704dc68ef27708e83a2a242355.zip gcc-643ef9571905ce704dc68ef27708e83a2a242355.tar.gz gcc-643ef9571905ce704dc68ef27708e83a2a242355.tar.bz2 | |
[aarch64] Fix obsolete comment about X30
r217431 changed X30 as caller-saved in CALL_USE_REGISTERS because of
which this comment about X30 not being marked as call-clobbered is no
longer accurate. Fixed to describe the current state more accurately.
* config/aarch64/aarch64.h (CALL_USE_REGISTERS): Fix obsolete
comment.
(EPILOGUE_USES): Likewise.
From-SVN: r262176
Diffstat (limited to 'gcc')
| -rw-r--r-- | gcc/ChangeLog | 6 | ||||
| -rw-r--r-- | gcc/config/aarch64/aarch64.h | 23 |
2 files changed, 17 insertions, 12 deletions
diff --git a/gcc/ChangeLog b/gcc/ChangeLog index 38e4ae2..773eeaa 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,9 @@ +2018-06-27 Siddhesh Poyarekar <siddhesh@sourceware.org> + + * config/aarch64/aarch64.h (CALL_USE_REGISTERS): Fix obsolete + comment. + (EPILOGUE_USES): Likewise. + 2018-06-26 Eric Botcazou <ebotcazou@adacore.com> * tree-inline.c (remap_location): New function extracted from... diff --git a/gcc/config/aarch64/aarch64.h b/gcc/config/aarch64/aarch64.h index 976f9af..f284e74 100644 --- a/gcc/config/aarch64/aarch64.h +++ b/gcc/config/aarch64/aarch64.h @@ -303,15 +303,6 @@ extern unsigned aarch64_architecture_version; register. GCC internally uses the poly_int variable aarch64_sve_vg instead. */ -/* Note that we don't mark X30 as a call-clobbered register. The idea is - that it's really the call instructions themselves which clobber X30. - We don't care what the called function does with it afterwards. - - This approach makes it easier to implement sibcalls. Unlike normal - calls, sibcalls don't clobber X30, so the register reaches the - called function intact. EPILOGUE_USES says that X30 is useful - to the called function. */ - #define FIXED_REGISTERS \ { \ 0, 0, 0, 0, 0, 0, 0, 0, /* R0 - R7 */ \ @@ -327,6 +318,13 @@ extern unsigned aarch64_architecture_version; 0, 0, 0, 0, 0, 0, 0, 0, /* P8 - P15 */ \ } +/* X30 is marked as caller-saved which is in line with regular function call + behavior since the call instructions clobber it; AARCH64_EXPAND_CALL does + that for regular function calls and avoids it for sibcalls. X30 is + considered live for sibcalls; EPILOGUE_USES helps achieve that by returning + true but not until function epilogues have been generated. This ensures + that X30 is available for use in leaf functions if needed. */ + #define CALL_USED_REGISTERS \ { \ 1, 1, 1, 1, 1, 1, 1, 1, /* R0 - R7 */ \ @@ -391,9 +389,10 @@ extern unsigned aarch64_architecture_version; V_ALIASES(28), V_ALIASES(29), V_ALIASES(30), V_ALIASES(31) \ } -/* Say that the epilogue uses the return address register. Note that - in the case of sibcalls, the values "used by the epilogue" are - considered live at the start of the called function. */ +/* Say that the return address register is used by the epilogue, but only after + epilogue generation is complete. Note that in the case of sibcalls, the + values "used by the epilogue" are considered live at the start of the called + function. */ #define EPILOGUE_USES(REGNO) \ (epilogue_completed && (REGNO) == LR_REGNUM) |