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| author | Miguel Sofer <miguel.sofer@gmail.com> | 2007-08-16 20:39:34 (GMT) |
|---|---|---|
| committer | Miguel Sofer <miguel.sofer@gmail.com> | 2007-08-16 20:39:34 (GMT) |
| commit | 58d90767821271f9546b8f34b7db85d896784941 (patch) | |
| tree | 21a230c65d3d1523d38ad7705c93e30312d51cb9 /generic | |
| parent | b41667264c8c24d55fc76ed14dd42747e88d044f (diff) | |
| download | tcl-58d90767821271f9546b8f34b7db85d896784941.zip tcl-58d90767821271f9546b8f34b7db85d896784941.tar.gz tcl-58d90767821271f9546b8f34b7db85d896784941.tar.bz2 | |
* generic/tclExecute.c: check the two most frequent instructions
before the switch. Reduces both runtime and obj size a tiny bit.
Diffstat (limited to 'generic')
| -rw-r--r-- | generic/tclExecute.c | 18 |
1 files changed, 17 insertions, 1 deletions
diff --git a/generic/tclExecute.c b/generic/tclExecute.c index 43bd58a..5b3185b 100644 --- a/generic/tclExecute.c +++ b/generic/tclExecute.c @@ -12,7 +12,7 @@ * See the file "license.terms" for information on usage and redistribution of * this file, and for a DISCLAIMER OF ALL WARRANTIES. * - * RCS: @(#) $Id: tclExecute.c,v 1.314 2007/08/14 21:04:28 msofer Exp $ + * RCS: @(#) $Id: tclExecute.c,v 1.315 2007/08/16 20:39:34 msofer Exp $ */ #include "tclInt.h" @@ -1640,6 +1640,21 @@ TclExecuteByteCode( } } + /* + * These two instructions account for 26% of all instructions (according + * to measurements on tclbench by Ben Vitale + * [http://www.cs.toronto.edu/syslab/pubs/tcl2005-vitale-zaleski.pdf] + * Resolving them before the switch reduces the cost of branch + * mispredictions, seems to improve runtime by 5% to 15%, and (amazingly!) + * reduces total obj size. + */ + + if (*pc == INST_LOAD_SCALAR1) { + goto instLoadScalar1; + } else if (*pc == INST_PUSH1) { + goto instPush1Peephole; + } + switch (*pc) { case INST_RETURN_IMM: { int code = TclGetInt4AtPtr(pc+1); @@ -2257,6 +2272,7 @@ TclExecuteByteCode( Tcl_Obj *objPtr; case INST_LOAD_SCALAR1: + instLoadScalar1: opnd = TclGetUInt1AtPtr(pc+1); varPtr = &(compiledLocals[opnd]); while (TclIsVarLink(varPtr)) { |