# The present patch to the ARM ELF linking code in binutils (made against
# binutils-2.21.1a) is a hack that affects the generation of Thumb->ARM
# call veneers.  The binutils linker can make these veneers in two forms:
#
#	"Short"			"Long"
#	(16-bit) bx pc		(16-bit) bx pc
#	(16-bit) nop		(16-bit) nop
#	(32-bit) b dest		(32-bit) ldr pc, [pc, #-4]
#				(32-bit) .long target
#
# For code that's going to run on the Calypso ARM7 processor, the
# "short" form is the one we want: because of the way the address space
# is laid out, the range of an ARM branch instruction will always be
# sufficient for us, whereas the long version is more costly in terms
# of the number of cycles required, especially when executing from
# external memory.
#
# Unfortunately, the code which decides between these two forms
# (located in the arm_type_of_stub() function in bfd/elf32-arm.c)
# is broken.  The original code (which you can see below in the
# "before" part of the patch hunk) exhibits two problems:
#
# 1. The distance that matters here is not from the original
#    call point to the destination, but from the stub to
#    the destination - and in this function we don't know
#    where the stub will end up.
#
# 2. Because it's an ARM branch, the limits should be
#    ARM_MAX_[BF]WD_BRANCH_OFFSET, not the THM_ ones.
#
# The 2nd problem would be trivial to fix, but the 1st one
# much less so: this function doesn't know where the stub
# will end up, and considering that for the present purpose
# of the FreeCalypso project always emitting the "short"
# version would be perfect, there is no justification for
# expending the time and effort to restructure the linker
# to do the proper relaxation for the case at hand.
#
# Therefore, the patch we apply is a hack: we simply force the
# use of the "short" form unconditionally.

*** elf32-arm.c	Wed May 11 07:29:12 2011
--- elf32-arm-patched.c	Mon Aug 19 03:24:38 2013
***************
*** 3203,3211 ****
  		   : arm_stub_long_branch_v4t_thumb_arm);
  
  	      /* Handle v4t short branches.  */
! 	      if ((stub_type == arm_stub_long_branch_v4t_thumb_arm)
! 		  && (branch_offset <= THM_MAX_FWD_BRANCH_OFFSET)
! 		  && (branch_offset >= THM_MAX_BWD_BRANCH_OFFSET))
  		stub_type = arm_stub_short_branch_v4t_thumb_arm;
  	    }
  	}
--- 3203,3209 ----
  		   : arm_stub_long_branch_v4t_thumb_arm);
  
  	      /* Handle v4t short branches.  */
! 	      if (stub_type == arm_stub_long_branch_v4t_thumb_arm)
  		stub_type = arm_stub_short_branch_v4t_thumb_arm;
  	    }
  	}