diff options
| author | Michael Meissner <meissner@linux.vnet.ibm.com> | 2015-06-10 17:15:25 +0000 |
|---|---|---|
| committer | Michael Meissner <meissner@linux.vnet.ibm.com> | 2015-06-10 17:15:25 +0000 |
| commit | ceb91d8ed5a1d4eb71a534b4e8d13546d3350a38 (patch) | |
| tree | 62f3fbe17d5236344806e845fb8a8f253dbe4064 | |
| parent | d770d93f5143d2921ee7b2d1b119cb08a83ebe5c (diff) | |
2015-06-10 Michael Meissner <meissner@linux.vnet.ibm.com>ibm/gcc-5-prefixes
Backport from mainline:
2015-06-10 Michael Meissner <meissner@linux.vnet.ibm.com>
PR target/66474
* doc/md.texi (Machine Constraints): Document that on the PowerPC
if you use a constraint that targets a VSX register, you must use
%x<n> in the template.
git-svn-id: https://gcc.gnu.org/svn/gcc/branches/ibm/gcc-5-prefixes@224333 138bc75d-0d04-0410-961f-82ee72b054a4
| -rw-r--r-- | gcc/doc/md.texi | 21 |
1 files changed, 21 insertions, 0 deletions
diff --git a/gcc/doc/md.texi b/gcc/doc/md.texi index 30d7775aba7..e991286afcc 100644 --- a/gcc/doc/md.texi +++ b/gcc/doc/md.texi @@ -3070,6 +3070,27 @@ Altivec vector register @item wa Any VSX register if the -mvsx option was used or NO_REGS. +When using any of the register constraints (@code{wa}, @code{wd}, +@code{wf}, @code{wg}, @code{wh}, @code{wi}, @code{wj}, @code{wk}, +@code{wl}, @code{wm}, @code{ws}, @code{wt}, @code{wu}, @code{wv}, +@code{ww}, or @code{wy}) that take VSX registers, you must use +@code{%x<n>} in the template so that the correct register is used. +Otherwise the register number output in the assembly file will be +incorrect if an Altivec register is an operand of a VSX instruction +that expects VSX register numbering. + +@smallexample +asm ("xvadddp %x0,%x1,%x2" : "=wa" (v1) : "wa" (v2), "wa" (v3)); +@end smallexample + +is correct, but: + +@smallexample +asm ("xvadddp %0,%1,%2" : "=wa" (v1) : "wa" (v2), "wa" (v3)); +@end smallexample + +is not correct. + @item wd VSX vector register to hold vector double data or NO_REGS. |