One of the more unfortunate things MIPS has inherited is an LP64 ABI
that uses 32-bit rather than 64-bit ELF. I've no idea how many people
use it these days (if anyone), but it happens to the ABI of the MIPS
primary target, mipsisa64-elf.
Because we're using 32-bit ELF, DWARF2_ADDR_SIZE is 4 rather than 8.
This currently causes problems with dwarf2out when we have an eliminated
expression such arg_pointer_rtx or arg_pointer_rtx + CONST. Normally we'd
treat them specially and apply the elimination, but this implicitly
requires Pmode to be no bigger than DWARF2_ADDR_SIZE:
case REG:
if (GET_MODE_CLASS (mode) != MODE_INT
|| (GET_MODE_SIZE (mode) > DWARF2_ADDR_SIZE
#ifdef POINTERS_EXTEND_UNSIGNED
&& (mode != Pmode || mem_mode == VOIDmode)
#endif
))
{
[...]
mem_loc_result = new_loc_descr (DW_OP_GNU_regval_type,
dbx_reg_number (rtl), 0);
[...]
}
if (REGNO (rtl) < FIRST_PSEUDO_REGISTER)
mem_loc_result = based_loc_descr (rtl, 0, VAR_INIT_STATUS_INITIALIZED);
[...]
case PLUS:
plus:
if (is_based_loc (rtl)
&& GET_MODE_SIZE (mode) <= DWARF2_ADDR_SIZE
&& GET_MODE_CLASS (mode) == MODE_INT)
mem_loc_result = based_loc_descr (XEXP (rtl, 0),
INTVAL (XEXP (rtl, 1)),
VAR_INIT_STATUS_INITIALIZED);
where based_loc_descr does the elimination.
So as things stand we take the first "if", and try to get the register
number of the fake arg_pointer_rtx. This was latent for a while
(at least in the sense of GCC testing, although probably not if
you actually tried to debug using it) until H.J.'s recent patch
to add an assert to dbx_reg_regnumber. Which just goes to show
how good an assert it is.
I realise it's a bit clunky, but is the attached patch OK?
Tested on mipsisa64-elf, where it restores the build, and on
x86_64-linux-gnu.
Richard
gcc/
* dwarf2out.c (mem_loc_descriptor): Ignore DWARF2_ADDR_SIZE
for frame- and argument-pointer reg+offset expressions.
Index: gcc/dwarf2out.c
===================================================================
--- gcc/dwarf2out.c 2012-06-23 13:32:55.723114868 +0100
+++ gcc/dwarf2out.c 2012-06-23 16:55:39.694558787 +0100
@@ -11183,6 +11183,8 @@ mem_loc_descriptor (rtx rtl, enum machin
case REG:
if (GET_MODE_CLASS (mode) != MODE_INT
|| (GET_MODE_SIZE (mode) > DWARF2_ADDR_SIZE
+ && rtl != frame_pointer_rtx
+ && rtl != arg_pointer_rtx
#ifdef POINTERS_EXTEND_UNSIGNED
&& (mode != Pmode || mem_mode == VOIDmode)
#endif
@@ -11455,7 +11457,9 @@ mem_loc_descriptor (rtx rtl, enum machin
case PLUS:
plus:
if (is_based_loc (rtl)
- && GET_MODE_SIZE (mode) <= DWARF2_ADDR_SIZE
+ && (GET_MODE_SIZE (mode) <= DWARF2_ADDR_SIZE
+ || XEXP (rtl, 0) == frame_pointer_rtx
+ || XEXP (rtl, 0) == arg_pointer_rtx)
&& GET_MODE_CLASS (mode) == MODE_INT)
mem_loc_result = based_loc_descr (XEXP (rtl, 0),
INTVAL (XEXP (rtl, 1)),
