ELF: Add -O0 (produce output as fast as possible) mode.

Description

ELF: Add -O0 (produce output as fast as possible) mode.

This patch redefines the default optimization level as 1 and adds
new level 0. In the command line, it is -O0. The flag disables
costly but optional features so that the linker produces semantically
correct but larger output quickly. Currently it only disables
section merging.

This flag is not intended to be used for final production linking.
It is intended to be used in compile-link-test cycle.

Time to link clang with debug info is about 2x faster with the flag.

Head:
13.24 seconds
Output size: 1227189664 bytes

With this patch:
7.41 seconds
Output size: 2490281784 bytes

Differential Revision: http://reviews.llvm.org/D19705

Details

Committed
ruiuApr 29 2016, 9:12 AM
Differential Revision
D19705: ELF: Add "fast link" mode.
Parents
rL268055: Recommitted r264281 "Supporting all entities declared in lexical scope in…
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