From 9a9ee0201749bd0da2889d655bb2f70778f80f1d Mon Sep 17 00:00:00 2001 From: vries Date: Fri, 4 Jul 2014 13:36:25 +0000 Subject: Improve documentation of earlyclobber 2014-07-04 Tom de Vries * doc/md.texi (@subsection Constraint Modifier Characters): Clarify combination of earlyclobber and read/write modifiers. git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@212297 138bc75d-0d04-0410-961f-82ee72b054a4 --- gcc/ChangeLog | 5 +++++ gcc/doc/md.texi | 5 ++++- 2 files changed, 9 insertions(+), 1 deletion(-) (limited to 'gcc') diff --git a/gcc/ChangeLog b/gcc/ChangeLog index a9f535079b3..7637d263554 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,8 @@ +2014-07-04 Tom de Vries + + * doc/md.texi (@subsection Constraint Modifier Characters): Clarify + combination of earlyclobber and read/write modifiers. + 2014-07-04 Tom de Vries * config/aarch64/aarch64-simd.md diff --git a/gcc/doc/md.texi b/gcc/doc/md.texi index 539865ea3da..fde67d7a01e 100644 --- a/gcc/doc/md.texi +++ b/gcc/doc/md.texi @@ -1582,7 +1582,10 @@ alternatives of this form often allows GCC to produce better code when only some of the inputs can be affected by the earlyclobber. See, for example, the @samp{mulsi3} insn of the ARM@. -@samp{&} does not obviate the need to write @samp{=}. +Furthermore, if the @dfn{earlyclobber} operand is also read/write operand, then +that operand is modified only after it's used. + +@samp{&} does not obviate the need to write @samp{=} or @samp{+}. @cindex @samp{%} in constraint @item % -- cgit v1.2.1