As Jeff suggested here: https://gcc.gnu.org/ml/gcc-patches/2014-08/msg00390.html this patch documents that the first operand to an RTX_AUTOINC is the automodified register.
Tested on x86_64-linux-gnu. OK to install? Thanks, Richard gcc/ * doc/rtl.texi (RTX_AUTOINC): Document that the first operand is the automodified register. Index: gcc/doc/rtl.texi =================================================================== --- gcc/doc/rtl.texi 2014-05-06 18:38:47.982200623 +0100 +++ gcc/doc/rtl.texi 2014-08-30 16:04:50.870456416 +0100 @@ -193,7 +193,8 @@ An RTX code for something that matches i @item RTX_AUTOINC An RTX code for an auto-increment addressing mode, such as -@code{POST_INC}. +@code{POST_INC}. @samp{XEXP (@var{x}, 0)} gives the auto-modified +register. @item RTX_EXTRA All other RTX codes. This category includes the remaining codes used