http://llvm.org/bugs/show_bug.cgi?id=17612
Bug ID: 17612
Summary: missed optimization for static constexpr field without
definition
Product: clang
Version: 3.3
Hardware: PC
OS: Linux
Status: NEW
Severity: normal
Priority: P
Component: C++11
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected], [email protected]
Classification: Unclassified
Created attachment 11388
--> http://llvm.org/bugs/attachment.cgi?id=11388&action=edit
test case
Consider the code in attachment. clang only properly optimizes the function
`f()' when it has a definition for the constexpr field `foo' in the same
compilation unit.
Note that I'm not complaining that I have to provide a definition for field
`foo'. But my choice for the compilation unit for this definition should not
affect performance?
$ clang++ -std=c++11 -O2 -Wall -c report.cpp && objdump -d report.o
report.o: file format elf64-x86-64
Disassembly of section .text:
0000000000000000 <_Z1fv>:
0: b8 01 00 00 00 mov $0x1,%eax
5: 83 3d 00 00 00 00 01 cmpl $0x1,0x0(%rip) # c <_Z1fv+0xc>
c: 74 05 je 13 <_Z1fv+0x13>
e: b8 02 00 00 00 mov $0x2,%eax
13: c3 retq
$ clang++ -DDEF -std=c++11 -O2 -Wall -c report.cpp && objdump -d report.o
report.o: file format elf64-x86-64
Disassembly of section .text:
0000000000000000 <_Z1fv>:
0: b8 01 00 00 00 mov $0x1,%eax
5: c3 retq
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