[patch] Thumb-2 Instructio relaxation

Paul Brook paul@codesourcery.com
Mon Aug 29 16:35:00 GMT 2005

The attached patch implements assembler relaxation for Thumb-2 instructions.

 There are two different classes of relaxation performed:
- PC-relative branch, adr and ldr instructions.
- Other (absolute) immediate operands. The current implementation This 
currently only knows how to handle literal constants, but I plan on teaching 
it how to handle symbolic constants.

I've removed the disassembled insn address matching from thumb32.d because 
it's a pain to keep consistent, and doesn't seem to provide any benefit. The 
size if the insn is implicitly checked by checking the hex opcode bytes.

Tested with cross to arm-none-eabi.


2005-08-28  Paul Brook  <paul@codesourcery.com>

	* config/tc-arm.c (arm_it): Add relax field.
	(T16_32_TAB): Add addi, addis, add_pc, add_sp, dec_sp, inc_sp,
	b, bcond, ldr_pc, ldr_pc2, ldr_sp, str_sp, subi, subis.
	(do_t_add_sub, do_t_addr, do_t_branch, do_t_ldst,
	do_t_mov_cmp): Allow relaxation.
	(output_relax_insn): New function.
	(put_thumb32_insn): New function.
	(output_inst): Use new functions.
	(md_assemble): Don't throw error on relaxable instructions.
	(insns): Change "b" entry from TCE(...) to tCE(...).
	(md_estimate_size_before_relax): Return 2.
	(md_convert_frag, relax_immediate, relax_adr, relax_addsub,
	relax_branch, arm_relax_frag): New functions.
	(arm_force_relocation): Return 0 for Thumb-2 immediate operand
	* config/tc-arm.h (md_convert_frag): Remove definition.
	(md_relax_frag): Define.
	(arm_relax_frag): Add prototype.
	* gas/arm/thumb2_relax.d: New test.
	* gas/arm/thumb2_relax.s: New test.
	* gas/arm/thumb32.d: Adjust expected results to include relaxation.
	* gas/arm/thumb32.s: Tweak for better coverage of relaxable
	instructions.  Remove load/store tests.
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