Bug 153025 – Trust the baseline profiling data on the need for untyped operands support.

• Status: ASSIGNED
• Component: JavaScriptCore

[Mark Lam]

Currently, the DFG Fixup Phase also checks for a bad exit before it fix up some node operands to be Untyped.  We should not have to do this.  If the baseline profiling data tells us to expect Untyped operands, then we should trust it and just do so.

[Mark Lam]

Created attachment 268791 [details]
proposed patch.

Let's run some benchmark numbers first.

[Mark Lam]

Created attachment 268810 [details]
x86_64 benchmark result.

[Mark Lam]

Created attachment 268811 [details]
x86 benchmark result.

[Mark Lam]

The 64-bit x86_64 bench results seems to be a wash, but ...
The 32-bit x86 bench results have some notable (and repeatable) differences:

                                                          base32                    new32                                       
JSRegress:
   int-or-other-div-then-get-by-val                  11.5779+-1.3119     ^      8.8859+-0.7558        ^ definitely 1.3029x faster
   int-or-other-mul-then-get-by-val                   4.9188+-0.6033     !      7.3859+-0.2823        ! definitely 1.5016x slower
   string-repeat-arith                              106.8525+-3.1640     ^     86.5845+-3.4652        ^ definitely 1.2341x faster

The 2 speed ups don't manifest on 64-bit.  The int-or-other-mul-then-get-by-val slow down, however, does seem to be repeatable and manifest on both 64-bit and 32-bit on re-test.  The fact that it didn't show up in the x86_64 bench results, could be due to noise wiping it out.

At minimum, I should investigate why int-or-other-mul-then-get-by-val is slowing down so much.

[Mark Lam]

After rebasing to ToT r196092 which uses B3, x86_64 is now showing regressions with this patch:

                                                          base64                    new64                                       
JSRegress:
   arguments-out-of-bounds                           11.0405+-0.3241     !     13.8526+-0.4265        ! definitely 1.2547x slower
   int-or-other-mul-then-get-by-val                   4.1402+-0.0788     !      6.7275+-0.5579        ! definitely 1.6249x slower
   int-or-other-sub-then-get-by-val                   5.0074+-0.1249     !      7.3338+-0.2195        ! definitely 1.4646x slower
   int-or-other-sub                                   3.8862+-0.1220     !      4.9586+-0.0986        ! definitely 1.2759x slower
   string-out-of-bounds                              10.8937+-0.3605     !     13.6555+-0.4237        ! definitely 1.2535x slower