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Improve setjmp()/longjmp() performance.

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Exception handling for the C backend used setjmp()/longjmp()
unconditionally. However, on POSIX systems, these functions save and
restore the signal mask, adding considerable overhead to exception
handling, even where no exceptions are involved. The compiler and
library now try to use either _setjmp()/_longjmp() or
sigsetjmp()/siglongjmp() where possible, marked by the defines
"nimRawSetjmp" and "nimSigSetjmp", respectively. The define
"nimStdSetjmp" can be used to revert to setjmp()/longjmp() instead.
This commit is contained in:
Reimer Behrends 2014-09-25 23:29:02 +02:00
commit f99c40f61b
4 changed files with 28 additions and 6 deletions
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9
compiler/ccgstmts.nim
View file

@ -832,7 +832,14 @@ proc genTry(p: BProc, t: PNode, d: var TLoc) =
discard cgsym(p.module, "E_Base")
linefmt(p, cpsLocals, "#TSafePoint $1;$n", safePoint)
linefmt(p, cpsStmts, "#pushSafePoint(&$1);$n", safePoint)
linefmt(p, cpsStmts, "$1.status = setjmp($1.context);$n", safePoint)
if isDefined("nimStdSetjmp"):
linefmt(p, cpsStmts, "$1.status = setjmp($1.context);$n", safePoint)
elif isDefined("nimSigSetjmp"):
linefmt(p, cpsStmts, "$1.status = sigsetjmp($1.context, 0);$n", safePoint)
elif isDefined("nimRawSetjmp"):
linefmt(p, cpsStmts, "$1.status = _setjmp($1.context);$n", safePoint)
else:
linefmt(p, cpsStmts, "$1.status = setjmp($1.context);$n", safePoint)
startBlock(p, "if ($1.status == 0) {$n", [safePoint])
var length = sonsLen(t)
add(p.nestedTryStmts, t)

2
compiler/cgen.nim
View file

@ -13,7 +13,7 @@ import
ast, astalgo, strutils, hashes, trees, platform, magicsys, extccomp,
options, intsets,
nversion, nimsets, msgs, crc, bitsets, idents, lists, types, ccgutils, os,
times, ropes, math, passes, rodread, wordrecg, treetab, cgmeth,
times, ropes, math, passes, rodread, wordrecg, treetab, cgmeth, condsyms,
rodutils, renderer, idgen, cgendata, ccgmerge, semfold, aliases, lowerings,
semparallel

2
compiler/condsyms.nim
View file

@ -136,3 +136,5 @@ proc initDefines*() =
declareSymbol("emulatedthreadvars")
if platform.OS[targetOS].props.contains(ospLacksThreadVars):
defineSymbol("emulatedthreadvars")
if isDefined("posix"):
defineSymbol("nimRawSetjmp")

21
lib/system/ansi_c.nim
View file

@ -78,10 +78,23 @@ when defined(macosx):
else:
template SIGBUS: expr = SIGSEGV
proc c_longjmp(jmpb: C_JmpBuf, retval: cint) {.
header: "<setjmp.h>", importc: "longjmp".}
proc c_setjmp(jmpb: C_JmpBuf): cint {.
header: "<setjmp.h>", importc: "setjmp".}
when defined(nimSigSetjmp) and not defined(nimStdSetjmp):
proc c_longjmp(jmpb: C_JmpBuf, retval: cint) {.
header: "<setjmp.h>", importc: "siglongjmp".}
template c_setjmp(jmpb: C_JmpBuf): cint =
proc c_sigsetjmp(jmpb: C_JmpBuf, savemask: cint): cint {.
header: "<setjmp.h>", importc: "sigsetjmp".}
c_sigsetjmp(jmpb, 0)
elif defined(nimRawSetjmp) and not defined(nimStdSetjmp):
proc c_longjmp(jmpb: C_JmpBuf, retval: cint) {.
header: "<setjmp.h>", importc: "_longjmp".}
proc c_setjmp(jmpb: C_JmpBuf): cint {.
header: "<setjmp.h>", importc: "_setjmp".}
else:
proc c_longjmp(jmpb: C_JmpBuf, retval: cint) {.
header: "<setjmp.h>", importc: "longjmp".}
proc c_setjmp(jmpb: C_JmpBuf): cint {.
header: "<setjmp.h>", importc: "setjmp".}
proc c_signal(sig: cint, handler: proc (a: cint) {.noconv.}) {.
importc: "signal", header: "<signal.h>".}