[COFF] Process /EXPORT option in fastpath
Patch by Takuto Ikuta.
This patch reduces lld link time of chromium's blink_core.dll in
component build.
Total size of input argument in .directives become nearly 300MB in the
build and almost all its content are /EXPORT.
To reduce time of parsing too many /EXPORT option in the build, I
introduce fastpath for /EXPORT in ArgParser::parseDirectives.
On my desktop machine, 4 times stats of the link time are like below.
Improved around 20%.
This patch
TotalSeconds : 8.
6217627
TotalSeconds : 8.
5402175
TotalSeconds : 8.
6855853
TotalSeconds : 8.
3624441
Ave : 8.
5525024
master
TotalSeconds : 10.
9975031
TotalSeconds : 11.
3409428
TotalSeconds : 10.
6332897
TotalSeconds : 10.
7650687
Ave : 10.
934201075
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@322117
91177308-0d34-0410-b5e6-
96231b3b80d8