[LLVMbugs] [Bug 2298] Missed optimization: should instcombine icmp ~A, ~B to icmp B, A

[bugzilla-daemon at cs.uiuc.edu]

http://llvm.org/bugs/show_bug.cgi?id=2298


Chris Lattner <sabre at nondot.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |FIXED




--- Comment #1 from Chris Lattner <sabre at nondot.org>  2008-05-09 00:21:23 ---
This triggered a quite a few times in multisource across several different
programs:
****    %tmp177.i = icmp slt i32 %tmp176.i17, -1                ; <i1>
[#uses=1]
...
****    %tmp42 = icmp ugt i32 %tmp35, %tmp40            ; <i1> [#uses=1]
****    %tmp27 = icmp ugt i32 %tmp23, %tmp26            ; <i1> [#uses=1]
****    %tmp33 = icmp ugt i32 %tmp30, %tmp32            ; <i1> [#uses=1]
...
****    %tmp23 = icmp ugt i32 %tmp17, %tmp22            ; <i1> [#uses=1]

****    %tmp18 = icmp ugt i32 %tmp13, %tmp17            ; <i1> [#uses=1]
....
****    %tmp42 = icmp ult i32 %tmp41, -4                ; <i1> [#uses=1]
...
****    %tmp24 = icmp ugt i32 %tmp14, %tmp22            ; <i1> [#uses=1]
****    %tmp37 = icmp ugt i32 %tmp29, %tmp35            ; <i1> [#uses=1]
****    %tmp27 = icmp ugt i32 %tmp21, %tmp26            ; <i1> [#uses=1]
****    %tmp41 = icmp ugt i32 %tmp32, %tmp39            ; <i1> [#uses=1]


I also implemented the '-x == -y' xform, which is only valid for equality
operators:
**** ---        %tmp14 = icmp eq i32 %tmp, -4           ; <i1> [#uses=1]
**** ---        %tmp436751 = icmp eq i32 %tmp441.rec, -2                ; <i1>
[#uses=1]

this seems to come from loop optimizations or something.  Lots of things that
use ".rec" as a suffix.

Patch here:
http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20080505/062193.html

Thanks!


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