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tcg/optimize: optimize "op r, a, a => movi r, 0"
Now that it's possible to detect copies, we can optimize the case the "op r, a, a => movi r, 0". This helps in the computation of overflow flags when one of the two args is 0. Reviewed-by: Richard Henderson <rth@twiddle.net> Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
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@ -540,6 +540,22 @@ static TCGArg *tcg_constant_folding(TCGContext *s, uint16_t *tcg_opc_ptr,
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break;
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}
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/* Simplify expression for "op r, a, a => movi r, 0" cases */
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switch (op) {
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CASE_OP_32_64(sub):
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CASE_OP_32_64(xor):
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if (temps_are_copies(args[1], args[2])) {
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gen_opc_buf[op_index] = op_to_movi(op);
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tcg_opt_gen_movi(gen_args, args[0], 0);
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gen_args += 2;
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args += 3;
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continue;
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}
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break;
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default:
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break;
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}
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/* Propagate constants through copy operations and do constant
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folding. Constants will be substituted to arguments by register
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allocator where needed and possible. Also detect copies. */
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