0, /* todo_flags_finish */
0 /* letter */
};
-\f
-
-/* This mini-pass fixes fall-out from SSA in asm statements that have
- in-out constraints. Say you start with
-
- orig = inout;
- asm ("": "+mr" (inout));
- use (orig);
-
- which is transformed very early to use explicit output and match operands:
-
- orig = inout;
- asm ("": "=mr" (inout) : "0" (inout));
- use (orig);
-
- Or, after SSA and copyprop,
-
- asm ("": "=mr" (inout_2) : "0" (inout_1));
- use (inout_1);
-
- Clearly inout_2 and inout_1 can't be coalesced easily anymore, as
- they represent two separate values, so they will get different pseudo
- registers during expansion. Then, since the two operands need to match
- per the constraints, but use different pseudo registers, reload can
- only register a reload for these operands. But reloads can only be
- satisfied by hardregs, not by memory, so we need a register for this
- reload, just because we are presented with non-matching operands.
- So, even though we allow memory for this operand, no memory can be
- used for it, just because the two operands don't match. This can
- cause reload failures on register-starved targets.
-
- So it's a symptom of reload not being able to use memory for reloads
- or, alternatively it's also a symptom of both operands not coming into
- reload as matching (in which case the pseudo could go to memory just
- fine, as the alternative allows it, and no reload would be necessary).
- We fix the latter problem here, by transforming
-
- asm ("": "=mr" (inout_2) : "0" (inout_1));
-
- back to
-
- inout_2 = inout_1;
- asm ("": "=mr" (inout_2) : "0" (inout_2)); */
-
-static void
-match_asm_constraints_1 (rtx insn, rtx *p_sets, int noutputs)
-{
- int i;
- rtx op = SET_SRC (p_sets[0]);
- int ninputs = ASM_OPERANDS_INPUT_LENGTH (op);
- rtvec inputs = ASM_OPERANDS_INPUT_VEC (op);
-
- for (i = 0; i < ninputs; i++)
- {
- rtx input, output, insns;
- const char *constraint = ASM_OPERANDS_INPUT_CONSTRAINT (op, i);
- char *end;
- int match;
-
- match = strtoul (constraint, &end, 10);
- if (end == constraint)
- continue;
-
- gcc_assert (match < noutputs);
- output = SET_DEST (p_sets[match]);
- input = RTVEC_ELT (inputs, i);
- if (rtx_equal_p (output, input)
- || (GET_MODE (input) != VOIDmode
- && GET_MODE (input) != GET_MODE (output)))
- continue;
-
- start_sequence ();
- emit_move_insn (copy_rtx (output), input);
- RTVEC_ELT (inputs, i) = copy_rtx (output);
- insns = get_insns ();
- end_sequence ();
-
- emit_insn_before (insns, insn);
- }
-}
-
-static void
-rest_of_match_asm_constraints (void)
-{
- basic_block bb;
- rtx insn, pat, *p_sets;
- int noutputs;
-
- if (!cfun->has_asm_statement)
- return;
-
- FOR_EACH_BB (bb)
- {
- FOR_BB_INSNS (bb, insn)
- {
- if (!INSN_P (insn))
- continue;
- pat = PATTERN (insn);
- if (GET_CODE (pat) == PARALLEL)
- p_sets = &XVECEXP (pat, 0, 0), noutputs = XVECLEN (pat, 0);
- else if (GET_CODE (pat) == SET)
- p_sets = &PATTERN (insn), noutputs = 1;
- else
- continue;
-
- if (GET_CODE (*p_sets) == SET
- && GET_CODE (SET_SRC (*p_sets)) == ASM_OPERANDS)
- match_asm_constraints_1 (insn, p_sets, noutputs);
- }
- }
-
- update_life_info_in_dirty_blocks (UPDATE_LIFE_GLOBAL_RM_NOTES,
- PROP_DEATH_NOTES | PROP_REG_INFO);
-}
-
-struct tree_opt_pass pass_match_asm_constraints =
-{
- "asmcons", /* name */
- NULL, /* gate */
- rest_of_match_asm_constraints, /* execute */
- NULL, /* sub */
- NULL, /* next */
- 0, /* static_pass_number */
- 0, /* tv_id */
- 0, /* properties_required */
- 0, /* properties_provided */
- 0, /* properties_destroyed */
- 0, /* todo_flags_start */
- TODO_dump_func, /* todo_flags_finish */
- 0 /* letter */
-};
#include "gt-function.h"
projects / thirdparty / gcc.git / commitdiff
