From: Andrew Carlotti <andrew.carlotti@arm.com>
Date: Wed, 18 Dec 2024 15:59:24 +0000 (+0000)
Subject: docs: Document new hardreg PRE pass
X-Git-Tag: basepoints/gcc-16~2763
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=016e2f00d40d76676f38fb9d268ac550e5ec878a;p=thirdparty%2Fgcc.git

docs: Document new hardreg PRE pass

gcc/ChangeLog:

	* doc/passes.texi: Document hardreg PRE pass.
---

diff --git a/gcc/doc/passes.texi b/gcc/doc/passes.texi
index 59a143292c78..282fc1a6a12b 100644
--- a/gcc/doc/passes.texi
+++ b/gcc/doc/passes.texi
@@ -959,6 +959,12 @@ global constant and  copy propagation.
 The source file for this pass is @file{gcse.cc}, and the LCM routines
 are in @file{lcm.cc}.
 
+A third version of this pass is run on some targets to optimise assignments to
+specific hard registers.  This can be used in cases where a register has a
+single purpose, such as specifying a mode as an extra input for specific
+instructions (@pxref{mode switching optimization} for another way of handling
+instruction modes).
+
 @item Loop optimization
 
 This pass performs several loop related optimizations.
@@ -1018,6 +1024,7 @@ combination approaches as well.
 The pass runs twice, once before register allocation and once after
 register allocation.  The code is located in @file{late-combine.cc}.
 
+@anchor{mode switching optimization}
 @item Mode switching optimization
 
 This pass looks for instructions that require the processor to be in a