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RE: [PATCH] Add target hook to override DWARF2 frame register size

> Please don't add target macros. Add a hook if you must, but we're
> supposed to remove target macros, not add new ones :-)

Thanks Steven, I wasn't sure if there were still things that were
acceptable as macros. There's a lot to get rid of still.

Updated patch using a target hook. I've opted to move the logic
which handles part clobbered registers into the default implementation
as that seemed natural. I have no real preference if others feel that
is the wrong thing to do. This will be used by an up-coming patch for
MIPS O32 ABI extensions.

Bootstrapped and regtested on x86_64-linux-gnu.


	* target.def (TARGET_DWARF_FRAME_REG_MODE): New target hook.
	* targhooks.c (default_dwarf_frame_reg_mode): New function.
	* targhooks.h (default_dwarf_frame_reg_mode): New prototype.
	* doc/ (TARGET_DWARF_FRAME_REG_MODE): Document.
	* doc/tm.texi: Regenerate.
	* dwarf2cfi.c (expand_builtin_init_dwarf_reg_sizes): Abstract mode
	selection logic to default_dwarf_frame_reg_mode.
 gcc/doc/tm.texi    |  7 +++++++
 gcc/doc/ |  2 ++
 gcc/dwarf2cfi.c    |  4 +---
 gcc/target.def     | 11 +++++++++++
 gcc/targhooks.c    | 13 +++++++++++++
 gcc/targhooks.h    |  1 +
 6 files changed, 35 insertions(+), 3 deletions(-)

diff --git a/gcc/doc/ b/gcc/doc/
index dd72b98..aa92ce4 100644
--- a/gcc/doc/
+++ b/gcc/doc/
@@ -6604,6 +6604,8 @@ the target supports DWARF 2 frame unwind information.
diff --git a/gcc/dwarf2cfi.c b/gcc/dwarf2cfi.c
index 85cfb60..a673106 100644
--- a/gcc/dwarf2cfi.c
+++ b/gcc/dwarf2cfi.c
@@ -271,11 +271,9 @@ expand_builtin_init_dwarf_reg_sizes (tree address)
       if (rnum < DWARF_FRAME_REGISTERS)
 	  HOST_WIDE_INT offset = rnum * GET_MODE_SIZE (mode);
-	  enum machine_mode save_mode = reg_raw_mode[i];
 	  HOST_WIDE_INT size;
+	  enum machine_mode save_mode = targetm.dwarf_frame_reg_mode (i);
-	  if (HARD_REGNO_CALL_PART_CLOBBERED (i, save_mode))
-	    save_mode = choose_hard_reg_mode (i, 1, true);
 	      if (save_mode == VOIDmode)
diff --git a/gcc/target.def b/gcc/target.def
index 3a41db1..d5aba51 100644
--- a/gcc/target.def
+++ b/gcc/target.def
@@ -3216,6 +3216,17 @@ If not defined, the default is to return @code{NULL_RTX}.",
  rtx, (rtx reg),
+/* Given a register return the mode of the corresponding DWARF frame
+   register.  */
+ "Given a register, this hook should return the mode which the\n\
+corresponding Dwarf frame register should have.  This is normally\n\
+used to return a smaller mode than the raw mode to prevent call\n\
+clobbered parts of a register altering the frame register size.",
+ enum machine_mode, (int regno),
+ default_dwarf_frame_reg_mode)
 /* If expand_builtin_init_dwarf_reg_sizes needs to fill in table
    entries not corresponding directly to registers below
    FIRST_PSEUDO_REGISTER, this hook should generate the necessary
diff --git a/gcc/targhooks.c b/gcc/targhooks.c
index 0f27a5a..765bf3b 100644
--- a/gcc/targhooks.c
+++ b/gcc/targhooks.c
@@ -1456,6 +1456,19 @@ default_debug_unwind_info (void)
   return UI_NONE;
+/* Determine the correct mode for a Dwarf frame register that represents
+   register REGNO.  */
+enum machine_mode
+default_dwarf_frame_reg_mode (int regno)
+  enum machine_mode save_mode = reg_raw_mode[regno];
+  if (HARD_REGNO_CALL_PART_CLOBBERED (regno, save_mode))
+    save_mode = choose_hard_reg_mode (regno, 1, true);
+  return save_mode;
 /* To be used by targets where reg_raw_mode doesn't return the right
    mode for registers used in apply_builtin_return and apply_builtin_arg.  */
diff --git a/gcc/targhooks.h b/gcc/targhooks.h
index 4be33f8..fa88679 100644
--- a/gcc/targhooks.h
+++ b/gcc/targhooks.h
@@ -194,6 +194,7 @@ extern int default_label_align_max_skip (rtx);
 extern int default_jump_align_max_skip (rtx);
 extern section * default_function_section(tree decl, enum node_frequency freq,
 					  bool startup, bool exit);
+extern enum machine_mode default_dwarf_frame_reg_mode (int);
 extern enum machine_mode default_get_reg_raw_mode (int);
 extern bool default_keep_leaf_when_profiled ();

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