https://gcc.gnu.org/g:63e7478db76452d9f7d5bef9704a94480cc28a77
commit r15-8087-g63e7478db76452d9f7d5bef9704a94480cc28a77
Author: Michal Jires <mji...@suse.cz>
Date: Thu Mar 13 16:18:10 2025 +0100
doc: document Incremental LTO flags
This adds missing documentation for LTO flags.
gcc/ChangeLog:
* doc/invoke.texi: (Optimize Options):
Add incremental LTO flags.
Diff:
---
gcc/doc/invoke.texi | 26 +++++++++++++++++++++++---
1 file changed, 23 insertions(+), 3 deletions(-)
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 768b98dba74c..26b3dd939617 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -601,7 +601,8 @@ Objective-C and Objective-C++ Dialects}.
-floop-block -floop-interchange -floop-strip-mine
-floop-unroll-and-jam -floop-nest-optimize
-floop-parallelize-all -flra-remat -flto -flto-compression-level
--flto-partition=@var{alg} -fmalloc-dce -fmerge-all-constants
+-flto-partition=@var{alg} -flto-incremental=@var{path}
+-flto-incremental-cache-size=@var{n} -fmalloc-dce -fmerge-all-constants
-fmerge-constants -fmodulo-sched -fmodulo-sched-allow-regmoves
-fmove-loop-invariants -fmove-loop-stores -fno-branch-count-reg
-fno-defer-pop -fno-fp-int-builtin-inexact -fno-function-cse
@@ -15053,8 +15054,10 @@ Specify the partitioning algorithm used by the
link-time optimizer.
The value is either @samp{1to1} to specify a partitioning mirroring
the original source files or @samp{balanced} to specify partitioning
into equally sized chunks (whenever possible) or @samp{max} to create
-new partition for every symbol where possible. Specifying @samp{none}
-as an algorithm disables partitioning and streaming completely.
+new partition for every symbol where possible or @samp{cache} to
+balance chunk sizes while keeping related symbols together for better
+caching in incremental LTO. Specifying @samp{none} as an algorithm
+disables partitioning and streaming completely.
The default value is @samp{balanced}. While @samp{1to1} can be used
as an workaround for various code ordering issues, the @samp{max}
partitioning is intended for internal testing only.
@@ -15062,6 +15065,23 @@ The value @samp{one} specifies that exactly one
partition should be
used while the value @samp{none} bypasses partitioning and executes
the link-time optimization step directly from the WPA phase.
+@opindex flto-incremental
+@item -flto-incremental=@var{path}
+Enable incremental LTO, with its cache in given existing directory.
+Can significantly shorten edit-compile cycles with LTO.
+
+When used with LTO (@option{-flto}), the output of translation units
+inside LTO is cached. Cached translation units are likely to be
+encountered again when recompiling with small code changes, leading to
+recompile time reduction.
+
+Multiple GCC instances can use the same cache in parallel.
+
+@opindex flto-incremental-cache-size
+@item -flto-incremental-cache-size=@var{n}
+Specifies number of cache entries in incremental LTO after which to prune
+old entries. This is a soft limit, temporarily there may be more entries.
+
@opindex flto-compression-level
@item -flto-compression-level=@var{n}
This option specifies the level of compression used for intermediate
