| Message ID | 4E0E0389.5040505@codesourcery.com |
|---|---|
| State | New |
| Headers | show |
On 07/01/2011 10:27 AM, Bernd Schmidt wrote: > * simplify-rtx.c (simplify_const_binary_operation): Use the > shift_truncation_mask hook instead of performing modulo by > width. Compare against mode precision, not bitsize. > * combine.c (combine_simplify_rtx, simplify_shift_const_1): > Use shift_truncation_mask instead of constructing the value > manually. Ok. r~
Bernd Schmidt <bernds@codesourcery.com> writes: > At some point we've grown a shift_truncation_mask hook, but we're not > using it everywhere we're masking shift counts. This patch changes the > instances I found. The documentation reads: Note that, unlike @code{SHIFT_COUNT_TRUNCATED}, this function does @emph{not} apply to general shift rtxes; it applies only to instructions that are generated by the named shift patterns. I think you need to update the documentation, and check that existing target definitions do in fact apply to shift rtxes as well. Richard
On 07/06/11 20:06, Richard Sandiford wrote: > Bernd Schmidt <bernds@codesourcery.com> writes: >> At some point we've grown a shift_truncation_mask hook, but we're not >> using it everywhere we're masking shift counts. This patch changes the >> instances I found. > > The documentation reads: > > Note that, unlike @code{SHIFT_COUNT_TRUNCATED}, this function does > @emph{not} apply to general shift rtxes; it applies only to instructions > that are generated by the named shift patterns. Ouch. That is one seriously misnamed hook then. > I think you need to update the documentation, and check that existing > target definitions do in fact apply to shift rtxes as well. Until I can do that, I've reverted this patch. Bernd
Bernd Schmidt <bernds@codesourcery.com> writes: > On 07/06/11 20:06, Richard Sandiford wrote: >> Bernd Schmidt <bernds@codesourcery.com> writes: >>> At some point we've grown a shift_truncation_mask hook, but we're not >>> using it everywhere we're masking shift counts. This patch changes the >>> instances I found. >> >> The documentation reads: >> >> Note that, unlike @code{SHIFT_COUNT_TRUNCATED}, this function does >> @emph{not} apply to general shift rtxes; it applies only to instructions >> that are generated by the named shift patterns. > > Ouch. That is one seriously misnamed hook then. Yeah. I take the blame for that, sorry :-( >> I think you need to update the documentation, and check that existing >> target definitions do in fact apply to shift rtxes as well. > > Until I can do that, I've reverted this patch. Thanks. Richard
Index: gcc/simplify-rtx.c =================================================================== --- gcc/simplify-rtx.c.orig +++ gcc/simplify-rtx.c @@ -3704,8 +3704,8 @@ simplify_const_binary_operation (enum rt shift_truncation_mask, since the shift might not be part of an ashlM3, lshrM3 or ashrM3 instruction. */ if (SHIFT_COUNT_TRUNCATED) - arg1 = (unsigned HOST_WIDE_INT) arg1 % width; - else if (arg1 < 0 || arg1 >= GET_MODE_BITSIZE (mode)) + arg1 &= targetm.shift_truncation_mask (mode); + else if (arg1 < 0 || arg1 >= GET_MODE_PRECISION (mode)) return 0; val = (code == ASHIFT Index: gcc/combine.c =================================================================== --- gcc/combine.c.orig +++ gcc/combine.c @@ -5941,9 +5941,7 @@ combine_simplify_rtx (rtx x, enum machin else if (SHIFT_COUNT_TRUNCATED && !REG_P (XEXP (x, 1))) SUBST (XEXP (x, 1), force_to_mode (XEXP (x, 1), GET_MODE (XEXP (x, 1)), - ((unsigned HOST_WIDE_INT) 1 - << exact_log2 (GET_MODE_BITSIZE (GET_MODE (x)))) - - 1, + targetm.shift_truncation_mask (GET_MODE (x)), 0)); break; @@ -9896,7 +9894,7 @@ simplify_shift_const_1 (enum rtx_code co want to do this inside the loop as it makes it more difficult to combine shifts. */ if (SHIFT_COUNT_TRUNCATED) - orig_count &= GET_MODE_BITSIZE (mode) - 1; + orig_count &= targetm.shift_truncation_mask (mode); /* If we were given an invalid count, don't do anything except exactly what was requested. */