Il 26/05/2012 14:35, Paolo Bonzini ha scritto: > /* We have to return > > z2 + ((u0 + u1) >> GET_MODE_BITSIZE (word_mode)). > > u0 + u1 are the upper two words of the three-word > intermediate result and they could have up to > 2 * GET_MODE_BITSIZE (word_mode) + 1 bits of precision. > We compute the extra bit by checking for carry, and add > 1 << GET_MODE_BITSIZE (word_mode) to z2 if there is carry. */
Oops, GET_MODE_BITSIZE (word_mode) is more concisely BITS_PER_WORD. >> > + tmp = expand_binop (mode, add_optab, u0, u1, tmp, 1, >> > OPTAB_LIB_WIDEN); >> > + if (!tmp) >> > + return 0; > /* We have to return z2 + (tmp >> 32). We need >> > + /* Checking for overflow. */ > This is not overflow, it's carry (see above). > >> > + c = gen_reg_rtx (mode); >> > + c1 = gen_reg_rtx (mode); >> > + cres = gen_reg_rtx (mode); >> > + >> > + emit_store_flag_force (c, GT, u0, tmp, mode, 1, 1); >> > + emit_store_flag_force (c1, GT, u1, tmp, mode, 1, 1); >> > + result = expand_binop (mode, ior_optab, c, c1, cres, 1, >> > OPTAB_LIB_WIDEN); >> > + if (!result) >> > + return 0; >> > + >> > + ccst = gen_reg_rtx (mode); >> > + ccst = expand_shift (LSHIFT_EXPR, mode, cres, 32, ccst, 1); > This 32 should be GET_MODE_BITSIZE (word_mode). Here, too. Paolo
