configure --enable-optimize doesn't seem to override CFG_DISABLE_OPTIMIZE

[catamorphism]

If CFG_DISABLE_OPTIMIZE is set in the environment, and I run ../configure --enable-optimize, I would expect an optimized build. However, this seems to have the effect of building an optimized LLVM but not an optimized rustc. (Doing VERBOSE=1 make rustc-stage1, I see the -O3 flag in the LLVM compile command lines, but no -O flag in the Rust compile commands.) The Makefile.in suggests my suspicion is right:

ifdef CFG_DISABLE_OPTIMIZE
  $(info cfg: disabling rustc optimization (CFG_DISABLE_OPTIMIZE))
  CFG_RUSTC_FLAGS +=
else
  CFG_RUSTC_FLAGS += -O
endif

If this is the intended behavior, it should at least be documented.

[catamorphism]

Nominating for milestone 5, production-ready

[catamorphism]

Just a bug

[flaper87]

Visiting for triage... Still valid.

This seems to be the expected behavior. However, I'd expect CFG_DISABLE_OPTIMIZE to be consistent throughout Rust's build. That is, CFG_DISABLE_OPTIMIZE should disable all optimization if set.

[huonw]

part of #8058

[emberian]

There are now separate flags for optimizing C++ and LLVM code respectively (--disable-optimize-cxx and --disable-optimize-llvm).