This patch adds a target macro to allow a backend to override the size
of a dwarf frame register. This is already supported to some extent
by allowing the HARD_REGNO_CALL_PART_CLOBBERED to reduce the size of
a specific register to only that which is saved. However, for the
new MIPS O32 FP64 ABI extension I need more control.
The standard MIPS O32 ABI has 32-bit floating point-registers which
are saved as pairs to form 64-bit values. The FP64 extension widens
all floating-point registers to 64-bit but only saves the even numbered
registers thus not increasing the callee-saved state. In order to
support interlinking between the standard O32 ABI and the extension I
must keep the layout of the frame information the same. The dwarf
frame registers are therefore re-interpreted to refer to the low and
high parts of even numbered 64-bit registers rather than 32 32-bit
registers. To achieve this I must artificially reduce the size of the
frame registers for the widened 64-bit registers down to 32-bit but
cannot use the HARD_REGNO_CALL_PART_CLOBBERED macro to achieve this.
Thanks,
Matthew
gcc/
* dwarf2cfi (DWARF_REG_MODE): Define with default implementation.
(expand_builtin_init_dwarf_reg_sizes): Use DWARF_REG_MODE.
* doc/tm.texi.in (DWARF_REG_MODE): Document.
* doc/tm.texi: Regenerate.
---
gcc/doc/tm.texi.in | 9 +++++++++
gcc/dwarf2cfi.c | 5 +++++
2 files changed, 14 insertions(+)
diff --git a/gcc/doc/tm.texi.in b/gcc/doc/tm.texi.in
index dd72b98..71799f7 100644
--- a/gcc/doc/tm.texi.in
+++ b/gcc/doc/tm.texi.in
@@ -2809,6 +2809,12 @@ in DWARF 2 debug information. The default is zero. A
different value
may reduce the size of debug information on some ports.
@end defmac
+@defmac DWARF_REG_MODE (@var{N}, @var{mode})
+If defined, a C expression whose value is a mode that should be used
+to represent the @var{N}th DWARF frame register. By default this is
+the same @var{mode} as the hard register it relates to.
+@end defmac
+
@node Exception Handling
@subsection Exception Handling Support
@cindex exception handling
diff --git a/gcc/dwarf2cfi.c b/gcc/dwarf2cfi.c
index 85cfb60..163db5d 100644
--- a/gcc/dwarf2cfi.c
+++ b/gcc/dwarf2cfi.c
@@ -252,6 +252,10 @@ init_return_column_size (enum machine_mode mode, rtx mem,
unsigned int c)
gen_int_mode (size, mode));
}
+#ifndef DWARF_REG_MODE
+#define DWARF_REG_MODE(REGNO, MODE) (MODE)
+#endif
+
/* Generate code to initialize the register size table. */
void
@@ -276,6 +280,7 @@ expand_builtin_init_dwarf_reg_sizes (tree address)
if (HARD_REGNO_CALL_PART_CLOBBERED (i, save_mode))
save_mode = choose_hard_reg_mode (i, 1, true);
+ save_mode = DWARF_REG_MODE (i, save_mode);
if (dnum == DWARF_FRAME_RETURN_COLUMN)
{
if (save_mode == VOIDmode)
--
1.9.4
