A limit of 500 was still a bit too high for some tests.

PR15000 has a testcase where the time to compile was bordering on 30s. When I
dropped the limit value to 100, it became a much more managable 6s. The compile
time seems to increase in a roughly linear fashion based on increasing the limit
value. (See the runtimes below.)

So, let's lower the limit to 100 so that they can get a more reasonable compile
time.

Limit Value  Time
-----------  ----
10           0.9744s
20           1.8035s
30           2.3618s
40           2.9814s
50           3.6988s
60           4.5486s
70           4.9314s
80           5.8012s
90           6.4246s
100          7.0852s
110          7.6634s
120          8.3553s
130          9.0552s
140          9.6820s
150          9.8804s
160         10.8901s
170         10.9855s
180         12.0114s
190         12.6816s
200         13.2754s
210         13.9942s
220         13.8097s
230         14.3272s
240         15.7753s
250         15.6673s
260         16.0541s
270         16.7625s
280         17.3823s
290         18.8213s
300         18.6120s
310         20.0333s
320         19.5165s
330         20.2505s
340         20.7068s
350         21.1833s
360         22.9216s
370         22.2152s
380         23.9390s
390         23.4609s
400         24.0426s
410         24.6410s
420         26.5208s
430         27.7155s
440         26.4142s
450         28.5646s
460         27.3494s
470         29.7255s
480         29.4646s
490         30.5001s


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@179713 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Analysis/MemoryDependenceAnalysis.cpp

@@ -47,9 +47,7 @@ STATISTIC(NumCacheCompleteNonLocalPtr,
           "Number of block queries that were completely cached");
 
 // Limit for the number of instructions to scan in a block.
-// FIXME: Figure out what a sane value is for this.
-//        (500 is relatively insane.)
-static const int BlockScanLimit = 500;
+static const int BlockScanLimit = 100;
 
 char MemoryDependenceAnalysis::ID = 0;