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diff lwasm/insn_rel.c @ 211:6f2e18f1fe67
Improve autobranchlength pragma
Improve detection of 8 bit relative offsets when autobranchlength is in
effect. This should eliminate all but the most obscure corner cases where
the 16 bit mode is selected when 8 bit mode will do.
| author | William Astle <lost@l-w.ca> |
|---|---|
| date | Sat, 09 Jun 2012 17:23:04 -0600 |
| parents | 2be2649841f8 |
| children | d0e9dbe9afbe |
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--- a/lwasm/insn_rel.c Sat Jun 09 16:25:19 2012 -0600 +++ b/lwasm/insn_rel.c Sat Jun 09 17:23:04 2012 -0600 @@ -50,6 +50,7 @@ lw_expr_t t, e1, e2; l -> lint = -1; + l -> maxlen = OPLEN(instab[l -> insn].ops[3]) + 2; if (CURPRAGMA(l, PRAGMA_AUTOBRANCHLENGTH) == 0) { l -> lint = instab[l -> insn].ops[1]; @@ -163,6 +164,23 @@ l -> lint = 16; } } + // size of 8-bit opcode + 8 bit offset + l -> len = OPLEN(instab[l -> insn].ops[2]) + 1; + as -> pretendmax = 1; + lwasm_reduce_expr(as, e2); + as -> pretendmax = 0; + l -> len = -1; + if (lw_expr_istype(e2, lw_expr_type_int)) + { + // it reduced to an integer; is it in 8 bit range? + offs = lw_expr_intval(e2); + if (offs >= -128 && offs <= 127) + { + // fits in 8 bits with a worst case scenario + l -> len = OPLEN(instab[l -> insn].ops[2]) + 1; + l -> lint = 8; + } + } lw_expr_destroy(e2); } if (lw_expr_istype(e, lw_expr_type_int))