[m-dev.] Patch: support for shared objects on ARM

[Sergey Khorev]

JF> That's great! I'll take a look at your (revised) patch sometime
JF> over the next few days.

That revised patch wasn't correct as well, I should have been more careful. Please have a look at the patch below. It is the last revision, I promise :)

diff -cr ../mercury-compiler-0.12.1.bak/configure.in ./configure.in
*** ../mercury-compiler-0.12.1.bak/configure.in	2005-12-06 08:09:07.000000000 +0300
--- ./configure.in	2005-12-15 10:31:59.000000000 +0300
***************
*** 1960,1966 ****
  # (Actually I don't know if `-fno-functions-cse' is really needed.
  # Maybe you can get away without it.  But better to err on the safe side...)
  #
! # For alpha and for mips, and probably on other architectures, when using
  # non-local gotos we need -fomit-frame-pointer, otherwise when compiling
  # with --no-c-optimize we run into a problem similar to the one above:
  # Gcc generates code which initializes the frame pointer in the
--- 1960,1966 ----
  # (Actually I don't know if `-fno-functions-cse' is really needed.
  # Maybe you can get away without it.  But better to err on the safe side...)
  #
! # For alpha, mips, and ARM, and probably on other architectures, when using
  # non-local gotos we need -fomit-frame-pointer, otherwise when compiling
  # with --no-c-optimize we run into a problem similar to the one above:
  # Gcc generates code which initializes the frame pointer in the
***************
*** 2025,2030 ****
--- 2025,2033 ----
  		mercury_cv_asm_labels=no
  		mercury_cv_gcc_labels=no
  		;;
+ 	arm*-*)
+ 		CFLAGS_FOR_GOTOS="$CFLAGS_FOR_GOTOS -fomit-frame-pointer"
+ 		;;
      # On hppa64, ia64 and powerpc64 the test programs appear to work, but
      # larger programs die with an Illegal Instruction fault.
      hppa64-*)
***************
*** 3432,3437 ****
--- 3435,3449 ----
  		    AC_MSG_RESULT(no)
  		fi
  		;;
+ 	arm*-linux|arm*-linux-gnu)
+ 		AC_MSG_RESULT(yes)
+ 		EXT_FOR_SHARED_LIB=so
+ 		EXT_FOR_LINK_WITH_PIC_OBJECTS=o
+ 		# One can build gcc with a default PIC register other than sl
+ 		# so let's force it. If you change this, 
+ 		# update MR_ARM_PIC_REG in runtime/mercury_goto.h as well.
+ 		CFLAGS_FOR_PIC="-mpic-register=sl $CFLAGS_FOR_PIC"
+ 		;;
  	*)
  		# CFLAGS_FOR_PIC is used by boehm_gc/Makefile when creating
  		# libgc.a.  If the system doesn't support shared libraries,
diff -cr ../mercury-compiler-0.12.1.bak/runtime/mercury_goto.h ./runtime/mercury_goto.h
*** ../mercury-compiler-0.12.1.bak/runtime/mercury_goto.h	2004-04-14 05:31:56.000000000 +0400
--- ./runtime/mercury_goto.h	2005-12-15 08:16:42.000000000 +0300
***************
*** 465,470 ****
--- 465,525 ----
  	"	.type _entry_" MR_STRINGIFY(label) ",#function\n"
    #endif
  
+ #elif defined(__arm__)
+ 
+   #if MR_PIC
+ 
+     /*
+     ** At each entry point, where we may have been jump to from
+     ** code in a difference C file, we need to set up the PIC register.
+     ** We do this by adding _GLOBAL_OFFSET_TABLE_ value to the PC register 
+     ** Current instruction address is (PC - 8) hence -(0b + 8)
+     ** (I don't understand the details exactly, this code is
+     ** basically copied from the output of `gcc -fpic -S' for a function
+     ** containing setjmp.)
+     ** A little bit more detail can be obtained from GCC source
+     ** (function arm_finalize_pic in gcc/config/arm/arm.c)
+     ** Note that `0f' means the label `0:' following the current
+     ** instruction, and `0b' means the label `0:' before the current
+     ** instruction.
+     ** GCC doesn't like when we clobber the PIC register but it seems we
+     ** can safely keep GCC uninformed because we just do GCC's work
+     ** and the PIC register is saved over call
+     ** Loading arbitrary immediate values into ARM registers is not possible
+     ** directly hence the .word directive in the code section and the branch 
+     ** instruction bypassing it.
+     ** If you change MR_ARM_PIC_REG, update CFLAGS_FOR_PIC (-mpic-register)
+     ** in configure.in.
+     */
+     #define MR_ARM_PIC_REG "sl"
+ 
+     #define MR_INLINE_ASM_FIXUP_REGS				\
+       "	    ldr	" MR_ARM_PIC_REG ", 1f\n"			\
+       "0:\n"							\
+       "	    add	" MR_ARM_PIC_REG ", pc, " MR_ARM_PIC_REG "\n"	\
+       "	    b 2f\n"						\
+       "1:\n"							\
+       "	    .word	_GLOBAL_OFFSET_TABLE_-(0b+8)\n"		\
+       "2:\n"
+ 
+     /* For Linux-ELF shared libraries, we need to declare that the type of labels
+     ** is #function (i.e. code, not data), otherwise the dynamic linker seems
+     ** to get confused, and we end up jumping into the data section.
+     ** Hence the `.type' directive below.
+     */
+     #ifdef __ELF__
+       #define MR_INLINE_ASM_ENTRY_LABEL_TYPE(label) \
+ 	  "	.type _entry_" MR_STRINGIFY(label) ",#function\n"
+     #endif
+ 
+     /*
+     ** Save few clock ticks branching past MR_INLINE_ASM_FIXUP_REGS
+     */
+     #define MR_ASM_FALLTHROUGH(label) \
+       goto MR_skip(label);
+ 
+   #endif
+ 
  #endif
  
  /* for other architectures, these macros have default definitions */
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