| Issue |
55431
|
| Summary |
lld runs LTO even if -fno-lto is passed
|
| Labels |
new issue
|
| Assignees |
|
| Reporter |
simone-gaia
|
Posted a SO question about this: https://stackoverflow.com/questions/72190379/lld-runs-lto-even-if-fno-lto-is-passed. Copying here the content:
I have a CMake project with several subprojects that create static libraries built with `-flto=thin`.
The project has a lot of tests that are linked against the aforementioned libraries. With LTO it takes a lot of time to build tests, therefore I have disabled LTO for tests using `-fno-lto`.
What I noticed though, is that `lld` performs LTO on tests even with `-fno-lto`. If I run the linker with `--time-trace` I can see that the majority of the time is spent on LTO.
My questions are:
1. Is this expected? If so I can assume that `lld` performs LTO whenever it finds the LTO info in the object it links.
2. If not, is there a way to disable this behavior? Adding `-fno-lto` to the compiler does not seem to work, and `lld` does not have a param to explicitly disable LTO.
3. If not, is this a bug? If this is a bug I will submit a repro.
This is how I handle `lto` in CMake:
```
# Enable Thin LTO only on non-test targets.
if(ENABLE_LTO)
if (IS_TEST)
target_compile_options(${TARGET} PRIVATE -fno-lto)
# Probably pointless.
target_link_options(${TARGET} PRIVATE -fno-lto)
else()
message(STATUS "ENABLE_LTO on target ${TARGET})")
target_compile_options(${TARGET} PRIVATE -flto=thin)
target_link_options(${TARGET} PRIVATE -flto=thin -Wl,--thinlto-cache-dir=${CMAKE_BINARY_DIR}/lto.cache)
endif()
endif()
```
The command that builds the tests does not contain `-flto=thin` at all, it only contains `-fno-lto`
![]()
_______________________________________________
llvm-bugs mailing list
llvm-bugs@lists.llvm.org
https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-bugs
