Re: Status and future of the LLVM backend

5 Dec 2014

      Hi,

Am Donnerstag, den 04.12.2014, 23:37 +0100 schrieb Joachim Breitner:
...
The problem is that in order to find out which linker is used, ghc calls
/usr/bin/gcc -Wl,-version
without passing the options from -optl, so the -fuse-ld=gold is not used
in this step. I’m a bit confused, because the code in getLinkerInfo'
looks like it should be passing them... ah, but only on HEAD, not in
7.8... and git blame tells me that I probably want to apply this patch:
commit e7b414a3cc0e27049f2608f5e0a00c47146cc46d
Author: Sebastian Dröge 
Date:   Tue Nov 18 12:40:20 2014 -0600
now gold is used, but if I set this in SRC_HC_OPTS, it is also passed to
the bootstrapping compiler, which does not work with gold.

So it seems I want to modify the "C compiler link flags" settings.

I tried to achieve this using

        Index: ghc-7.8.20141119/aclocal.m4
        ===================================================================
        --- ghc-7.8.20141119.orig/aclocal.m4
        +++ ghc-7.8.20141119/aclocal.m4
        @@ -553,6 +553,10 @@ AC_DEFUN([FPTOOLS_SET_C_LD_FLAGS],
                 $3="$$3 -D_HPUX_SOURCE"
                 $5="$$5 -D_HPUX_SOURCE"
                 ;;
        +    arm*)
        +        # On arm, link using gold
        +        $3="$$3 -fuse-ld=gold"
        +        ;;
             esac

             # If gcc knows about the stack protector, turn it off.

but this made the settings reach parts of the build system where I did
not want them, and for example tips over configuring
terminfo-0.4.0.0...:

        checking for setupterm in -ltinfo... yes
        configure: creating ./config.status
        config.status: creating terminfo.buildinfo
        configure: WARNING: unrecognized options: --with-compiler, --with-gcc
        ghc-cabal: Missing dependency on a foreign library:
        * Missing C library: tinfo
        This problem can usually be solved by installing the system package that
        provides this library (you may need the "-dev" version). If the library is
        already installed but in a non-standard location then you can use the flags
        --extra-include-dirs= and --extra-lib-dirs= to specify where it is.

because --gcc-options=-fuse-ld=gold is being passed to ./configure. Now
idea why that confuses ghc-cabal.

Unfortunately, cabal is not very verbose and does not tell me why and
how the test C program failed to compile.... but strace helps. And we
are back at

/usr/bin/ld.gold: --hash-size=31: unknown option

But I’m not sure where this comes from.

So, less elegantly, I’m now trying

        @@ -487,7 +487,7 @@ AC_DEFUN([FP_SETTINGS],
                 fi
             fi
             SettingsCCompilerFlags="$CONF_CC_OPTS_STAGE2"
        -    SettingsCCompilerLinkFlags="$CONF_GCC_LINKER_OPTS_STAGE2"
        +    SettingsCCompilerLinkFlags="$CONF_GCC_LINKER_OPTS_STAGE2 -fuse-ld=gold"
             SettingsLdFlags="$CONF_LD_LINKER_OPTS_STAGE2"
             AC_SUBST(SettingsCCompilerCommand)
             AC_SUBST(SettingsHaskellCPPCommand)

Greetings,
Joachim

-- 
Joachim “nomeata” Breitner
  mail@joachim-breitner.de • http://www.joachim-breitner.de/
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