diff options
| author | H.J. Lu <hongjiu.lu@intel.com> | 2014-02-27 19:54:56 +0000 |
|---|---|---|
| committer | H.J. Lu <hjl@gcc.gnu.org> | 2014-02-27 11:54:56 -0800 |
| commit | c4f6267be502cf7fde69acb0c3d8b4bcb175f3a4 (patch) | |
| tree | cbba9d399879045199ff562c3d3da4cd893f2157 /gcc | |
| parent | 7a76df7f955128bb5c70d67bf428b8996ad48d42 (diff) | |
| download | gcc-c4f6267be502cf7fde69acb0c3d8b4bcb175f3a4.zip gcc-c4f6267be502cf7fde69acb0c3d8b4bcb175f3a4.tar.gz gcc-c4f6267be502cf7fde69acb0c3d8b4bcb175f3a4.tar.bz2 | |
Copy changes from doc/tm.texi to doc/tm.texi.in
* doc/tm.texi.in (Condition Code Status): Update documention for
relative locations of cc0-setter and cc0-user.
From-SVN: r208205
Diffstat (limited to 'gcc')
| -rw-r--r-- | gcc/ChangeLog | 5 | ||||
| -rw-r--r-- | gcc/doc/tm.texi.in | 9 |
2 files changed, 12 insertions, 2 deletions
diff --git a/gcc/ChangeLog b/gcc/ChangeLog index 16c499b..60e7d9e 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,8 @@ +2014-02-27 H.J. Lu <hongjiu.lu@intel.com> + + * doc/tm.texi.in (Condition Code Status): Update documention for + relative locations of cc0-setter and cc0-user. + 2014-02-27 Jeff Law <law@redhat.com> PR rtl-optimization/52714 diff --git a/gcc/doc/tm.texi.in b/gcc/doc/tm.texi.in index 50f412c..6dcbde4 100644 --- a/gcc/doc/tm.texi.in +++ b/gcc/doc/tm.texi.in @@ -4484,8 +4484,13 @@ most instructions do not affect it. The latter category includes most RISC machines. The implicit clobbering poses a strong restriction on the placement of -the definition and use of the condition code, which need to be in adjacent -insns for machines using @code{(cc0)}. This can prevent important +the definition and use of the condition code. In the past the definition +and use were always adjacent. However, recent changes to support trapping +arithmatic may result in the definition and user being in different blocks. +Thus, there may be a @code{NOTE_INSN_BASIC_BLOCK} between them. Additionally, +the definition may be the source of exception handling edges. + +These restrictions can prevent important optimizations on some machines. For example, on the IBM RS/6000, there is a delay for taken branches unless the condition code register is set three instructions earlier than the conditional branch. The instruction |