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);
+}
+
+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
