On 2018-02-09 09:10:25 -0600, Merlin Moncure wrote: > Question: when watching the compilation log, I see quite a few files > being compiled with both O2 and O1, for example: > > clang -Wall -Wmissing-prototypes -Wpointer-arith > -Wdeclaration-after-statement -Wendif-labels > -Wmissing-format-attribute -Wformat-security -fno-strict-aliasing > -fwrapv -Wno-unused-command-line-argument -O2 -O1 > -Wno-ignored-attributes -Wno-unknown-warning-option > -Wno-ignored-optimization-argument -I../../../../src/include > -D_GNU_SOURCE -I/home/mmoncure/llvm/include -DLLVM_BUILD_GLOBAL_ISEL > -D_GNU_SOURCE -D_DEBUG -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS > -D__STDC_LIMIT_MACROS -flto=thin -emit-llvm -c -o nbtsort.bc > nbtsort.c > > Is this intentional? (didn't check standard compilation, it just jumped out).
It stemms from the following hunk in Makefile.global.in about emitting bitcode: # Add -O1 to the options as clang otherwise will emit 'noinline' # attributes everywhere, making JIT inlining impossible to test in a # debugging build. # # FIXME: While LLVM will re-optimize when emitting code (after # inlining), it'd be better to only do this if -O0 is specified. %.bc : CFLAGS +=-O1 %.bc : %.c $(COMPILE.c.bc) -o $@ $< Inspecting the clang source code it's impossible to stop clang from emitting noinline attributes for every function on -O0. I think it makes sense to change this to filtering out -O0 and only adding -O1 if that's not present. :/ Greetings, Andres Freund