[GHC] #5824: ARM StgRun register clobber list is broken

[GHC]

#5824: ARM StgRun register clobber list is broken
-------------------------------+--------------------------------------------
    Reporter:  bgamari         |       Owner:  simonmar        
        Type:  bug             |      Status:  patch           
    Priority:  high            |   Milestone:  7.4.2           
   Component:  Runtime System  |     Version:  7.4.1-rc2       
    Keywords:                  |          Os:  Unknown/Multiple
Architecture:  arm             |     Failure:  None/Unknown    
  Difficulty:  Unknown         |    Testcase:                  
   Blockedby:                  |    Blocking:                  
     Related:                  |  
-------------------------------+--------------------------------------------

Comment(by nomeata):

 I hope you don’t mind using the ticket also as a experiment record. Maybe
 it helps some.

 So this is the gcc call that ghc is using to compile the c file and which
 fails:
 {{{
 /usr/bin/gcc -fno-stack-protector -Wl,--hash-size=31 -Wl,--reduce-memory-
 overheads -x c rts/StgCRun.c -o rts/StgCRun.s -S -Wimplicit -O
 -D__GLASGOW_HASKELL__=704 -DTABLES_NEXT_TO_CODE -Wall -Wextra -Wstrict-
 prototypes -Wmissing-prototypes -Wmissing-declarations -Winline
 -Waggregate-return -Wpointer-arith -Wmissing-noreturn -Wnested-externs
 -Wredundant-decls -Iincludes -Irts -Irts/dist/build -DCOMPILING_RTS
 -DUSE_LIBFFI_FOR_ADJUSTORS -fno-strict-aliasing -fno-common -g -O0
 -DRtsWay="rts_debug" -w -DDEBUG -mlong-calls -I includes -I rts -I
 rts/dist/build -I rts/dist/build -I rts/dist/build/autogen -I
 /home/nomeata/ghc-7.4.1/libraries/base/include -I
 /home/nomeata/ghc-7.4.1/rts/dist/build -I /home/nomeata/ghc-7.4.1/includes
 -I /home/nomeata/ghc-7.4.1/includes/dist-ghcconstants/header -I
 /home/nomeata/ghc-7.4.1/includes/dist-derivedconstants/header
 }}}

 Just reverting [5a984f4388ef85d5c3af973b21a12c12b36c1ed4] does not help.
 What does help is to remove both r11 and fp:
 {{{
 --- rts/StgCRun.c.orig  2012-02-12 22:02:56.000000000 +0000
 +++ rts/StgCRun.c       2012-02-12 22:02:59.000000000 +0000
 @@ -672,7 +672,7 @@
          "ldmfd sp!, {r4-r11, fp, ip, lr}\n\t"
        : "=r" (r)
        : "r" (f), "r" (basereg), "i" (RESERVED_C_STACK_BYTES)
 -      : "%r4", "%r5", "%r6", "%r8", "%r9", "%r10", "%r11", "%fp", "%ip",
 "%lr"
 +      : "%r4", "%r5", "%r6", "%r8", "%r9", "%r10",  "%ip", "%lr"
      );
      return r;
  }
 }}}

 But someone who actually knows what that means should tell me if it is a
 sensible thing to do.

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/5824#comment:17>
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