https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64150
Bug ID: 64150
Summary: Missed optimisation opportunity with moved-from pimpl
classes and a nullptr d-pointer
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: enhancement
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: marc at kdab dot com
Created attachment 34162
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=34162&action=edit
Sample program
When compiling attached sample program to assembler source, the compiler emits
two calls to destroy(), one for p1 and one for p2. However, it should be
statically clear that p1.d == nullptr, always, so dead code elimination should
remove the check for nullptr, the branch and the call to destroy().
$ g++ -v
Using built-in specs.
COLLECT_GCC=g++
COLLECT_LTO_WRAPPER=/opt/gcc/trunk/libexec/gcc/x86_64-unknown-linux-gnu/5.0.0/lto-wrapper
Target: x86_64-unknown-linux-gnu
Configured with: ../gcc/configure --prefix=/opt/gcc/trunk
--program-suffix=-trunk --enable-checking=release
--enable-languages=c,c++,go,fortran,objc,obj-c++ : (reconfigured)
../gcc/configure --prefix=/opt/gcc/trunk --enable-checking=release
--enable-languages=c,c++,go,fortran,objc,obj-c++
Thread model: posix
gcc version 5.0.0 20141015 (experimental) (GCC)
