From 34386e79b36040307ba65076cc09cb65ccfe1d66 Mon Sep 17 00:00:00 2001 From: Tom de Vries Date: Fri, 4 Jul 2014 13:36:25 +0000 Subject: [PATCH] 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. From-SVN: r212297 --- gcc/ChangeLog | 5 +++++ gcc/doc/md.texi | 5 ++++- 2 files changed, 9 insertions(+), 1 deletion(-) diff --git a/gcc/ChangeLog b/gcc/ChangeLog index a9f535079b36..7637d2635542 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 539865ea3da8..fde67d7a01ef 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 % -- 2.47.3