https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90217
Bug ID: 90217
Summary: Greater optimization of C++ Code
Product: gcc
Version: 8.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: stevexiong98 at hotmail dot com
Target Milestone: ---
Hi,
This is not so much a bug, but more of an enhancement. There are 2 pieces of
code I have listed below which should translate to identical assembly
instructions at high levels of compiler optimization (level 3) but currently do
not.
https://godbolt.org/z/Zn7FMK
https://godbolt.org/z/wB8eZd
Using ARM GCC 8.2, the code in the second link involves the stack pointer and
extra load/store operations to the newly-created stack space. There are more
assembly instructions in link 2's code than in link 1's code.
However, in Godbolt if you switch the compiler to Clang, at optimization 3 both
pieces of code manage to compile down to the same minimal Assembly
instructions.
Switching the compiler to x86-64 GCC (trunk), the code in the second link also
has a few extra operations compared the first link's code.
Is it possible to set ARM GCC and x86-64 GCC to a particular optimization
setting that allows both links' code to have matching assembly instructions? If
not, is it possible that in a future release, both compilers could apply enough
optimizations so that the assembly in link 1 matches link 2?
Thanks
