https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88971
Bug ID: 88971
Summary: Branch optimization inconsistency (missed
optimization)
Product: gcc
Version: 8.2.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: maratrus at mail dot ru
Target Milestone: ---
Created attachment 45490
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=45490&action=edit
A code that demonstrates different patterns in optimization technique
In the code attached I expect the compiler not to generate any code between two
`mfence` instructions in the method `CheckAndPrint()`.
Indeed, it does the good job if I call `PrintGood<false>()` method and no code
is generated. But if I out-comment `PrintBad<false>()` or even simple return
the compiler generates a code for the if-expression `if (t.j > 0)`.
In all three cases there seems to be no reason to generate any code.
The code attached is compiled as:
`g++ -std=c++11 -Ofast opt_template.cc -o opt_template`
I must be missing something but is there a good reason why the compiler managed
to optimize the code in one case but non in the other two?
