Hi,
On Mon, 7 Sep 2015, Kugan wrote:
> Allow GIMPLE_DEBUG with values in promoted register.
Patch does much more.
> gcc/ChangeLog:
>
> 2015-09-07 Kugan Vivekanandarajah <kug...@linaro.org>
>
> * expr.c (expand_expr_real_1): Set proper SUNREG_PROMOTED_MODE for
> SSA_NAME that was set by GIMPLE_CALL and assigned to another
> SSA_NAME of same type.
ChangeLog doesn't match patch, and patch contains dubious changes:
> --- a/gcc/cfgexpand.c
> +++ b/gcc/cfgexpand.c
> @@ -5240,7 +5240,6 @@ expand_debug_locations (void)
> tree value = (tree)INSN_VAR_LOCATION_LOC (insn);
> rtx val;
> rtx_insn *prev_insn, *insn2;
> - machine_mode mode;
>
> if (value == NULL_TREE)
> val = NULL_RTX;
> @@ -5275,16 +5274,6 @@ expand_debug_locations (void)
>
> if (!val)
> val = gen_rtx_UNKNOWN_VAR_LOC ();
> - else
> - {
> - mode = GET_MODE (INSN_VAR_LOCATION (insn));
> -
> - gcc_assert (mode == GET_MODE (val)
> - || (GET_MODE (val) == VOIDmode
> - && (CONST_SCALAR_INT_P (val)
> - || GET_CODE (val) == CONST_FIXED
> - || GET_CODE (val) == LABEL_REF)));
> - }
>
> INSN_VAR_LOCATION_LOC (insn) = val;
> prev_insn = PREV_INSN (insn);
So it seems that the modes of the values location and the value itself
don't have to match anymore, which seems dubious when considering how a
debugger should load the value in question from the given location. So,
how is it supposed to work?
And this change:
> --- a/gcc/rtl.h
> +++ b/gcc/rtl.h
> @@ -2100,6 +2100,8 @@ wi::int_traits <rtx_mode_t>::decompose (HOST_WIDE_INT*,
> targets is 1 rather than -1. */
> gcc_checking_assert (INTVAL (x.first)
> == sext_hwi (INTVAL (x.first), precision)
> + || INTVAL (x.first)
> + == (INTVAL (x.first) & ((1 << precision) - 1))
> || (x.second == BImode && INTVAL (x.first) ==
> 1));
>
> return wi::storage_ref (&INTVAL (x.first), 1, precision);
implies that wide_ints are not always sign-extended anymore after you
changes. That's a fundamental assumption, so removing that assert implies
that you somehow created non-canonical wide_ints, and those will cause
bugs elsewhere in the code. Don't just remove asserts, they are usually
there for a reason, and without accompanying changes those reasons don't
go away.
Ciao,
Michael.
