Compiling the attached source with the following options
-Wall -fno-exceptions -O2 -fprofile-use=/blah -fno-rtti
will result in a code with infinite loop.
In DCE, special code is added to handle dead loops conservatively. However this
requires PDOM information (control dep info) to be valid. The PDOM is created
in unintialized variable warning, but gets invalidated before cddce pass (the
incremental update does not work well). With the wrong CD info, DCE pass tries
to eliminate the loop, but the exit edge fixup code ends up linking the
precessor not to its post-dom bb, but to itself -- leading to infinite loop.
A proposed patch will be posted to gcc-patches.
David
--
Summary: Invalid PDOM lead to infinite loop to be generated
Product: gcc
Version: 4.4.0
Status: UNCONFIRMED
Keywords: wrong-code
Severity: normal
Priority: P3
Component: tree-optimization
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: davidxl at gcc dot gnu dot org
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39557
