Precompiling larger headers can save a lot of compile time across
various compilation units.
For the time being, disable precompiled headers for ccache builds on Windows
due to issues with reliably passing the appropriate options to ccache.
Selected compile time & memory improvements are as follows:
flang/lib/Parser/Fortran-parsers.cpp:
Elapsed (wall clock) time (h:mm:ss or m:ss): 0:47.31 -> 0:41.68
Maximum resident set size (kbytes): 2062140 -> 1745584
flang/lib/Lower/Bridge.cpp:
Elapsed (wall clock) time (h:mm:ss or m:ss): 1:19.16 -> 0:45.86
Maximum resident set size (kbytes): 3849144 -> 2443476
flang/lib/Lower/PFTBuilder.cpp
Elapsed (wall clock) time (h:mm:ss or m:ss): 1:29.24 -> 1:00.99
Maximum resident set size (kbytes): 4218368 -> 2923128
flang/lib/Lower/Allocatable.cpp
Elapsed (wall clock) time (h:mm:ss or m:ss): 0:53.03 -> 0:22.50
Maximum resident set size (kbytes): 3092840 -> 2116908
flang/lib/Semantics/Semantics.cpp
Elapsed (wall clock) time (h:mm:ss or m:ss): 1:18.75 -> 1:00.20
Maximum resident set size (kbytes): 3527744 -> 2545308
While the newly added precompiled headers are as follows:
Parser:
Elapsed (wall clock) time (h:mm:ss or m:ss): 0:09.62
Maximum resident set size (kbytes): 1034608
Lower:
Elapsed (wall clock) time (h:mm:ss or m:ss): 0:41.33
Maximum resident set size (kbytes): 3615240
Semantics:
Elapsed (wall clock) time (h:mm:ss or m:ss): 0:26.69
Maximum resident set size (kbytes): 2403776
---------
Signed-off-by: Kajetan Puchalski <kajetan.puchalski@arm.com>
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