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(location_attribute): If DECL_RTL looks like (MEM pseudo),

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treat that variable as optimized away.

From-SVN: r2253
This commit is contained in:
Richard Stallman 1992-09-26 20:40:25 +00:00
parent 68703794d6
commit 28b039e302
1 changed files with 33 additions and 7 deletions
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40
gcc/dwarfout.c
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@ -1478,7 +1478,19 @@ output_mem_loc_descriptor (rtl)
be referred to as a "base register". This distinction is not
based in any way upon what category of register the hardware
believes the given register belongs to. This is strictly
Dwarf terminology we're dealing with here. */
Dwarf terminology we're dealing with here.
Note that in cases where the location of a memory-resident data
object could be expressed as:
OP_ADD (OP_BASEREG (basereg), OP_CONST (0))
the actual DWARF location descriptor that we generate may just
be OP_BASEREG (basereg). This may look deceptively like the
object in question was allocated to a register (rather than
in memory) so DWARF consumers need to be aware of the subtle
distinction between OP_REG and OP_BASEREG.
*/
ASM_OUTPUT_DWARF_STACK_OP (asm_out_file, OP_BASEREG);
ASM_OUTPUT_DWARF_DATA4 (asm_out_file,
@ -1877,13 +1889,27 @@ location_attribute (rtl)
/* Handle a special case. If we are about to output a location descriptor
for a variable or parameter which has been optimized out of existence,
don't do that. Instead we output a zero-length location descriptor
value as part of the location attribute. Note that we cannot simply
suppress the entire location attribute, because the absence of a
location attribute in certain kinds of DIEs is used to indicate some-
thing entirely different... i.e. that the DIE represents an object
declaration, but not a definition. So sayeth the PLSIG. */
value as part of the location attribute.
if (! is_pseudo_reg (rtl))
A variable which has been optimized out of existance will have a
DECL_RTL value which denotes a pseudo-reg.
Currently, in some rare cases, variables can have DECL_RTL values
which look like (MEM (REG pseudo-reg#)). These cases are due to
bugs elsewhere in the compiler. We treat such cases
as if the variable(s) in question had been optimized out of existance.
Note that in all cases where we wish to express the fact that a
variable has been optimized out of existance, we do not simply
suppress the generation of the entire location attribute because
the absence of a location attribute in certain kinds of DIEs is
used to indicate something else entirely... i.e. that the DIE
represents an object declaration, but not a definition. So sayeth
the PLSIG.
*/
if (! is_pseudo_reg (rtl)
&& (GET_CODE (rtl) != MEM || ! is_pseudo_reg (XEXP (rtl, 0))))
output_loc_descriptor (eliminate_regs (rtl, 0, NULL_RTX));
ASM_OUTPUT_LABEL (asm_out_file, end_label);