On 17/01/17 13:57, Richard Earnshaw (lists) wrote:
On 16/01/17 14:29, Jiong Wang wrote:
I can see the reason for doing this is if you want to seperate the
interpretion
of GCC CFA reg-note and the final DWARF CFA operation. My
understanding is all
reg notes defined in gcc/reg-note.def should have general meaning,
even the
CFA_WINDOW_SAVE. For those which are architecture specific we might
need a
mechanism to define them in backend only.
For general reg-notes in gcc/reg-note.def, they are not always have
the
corresponding standard DWARF CFA operation, for example CFA_WINDOW_SAVE,
therefore if we want to achieve what you described, I think we also
need to
define a new target hook which maps a GCC CFA reg-note into
architecture DWARF
CFA operation.
Regards,
Jiong
Here is the patch.
Hmm, I really wasn't expecting any more than something like the
following in dwarf2cfi.c:
@@ -2098,7 +2098,9 @@ dwarf2out_frame_debug (rtx_insn *insn)
handled_one = true;
break;
+ case REG_CFA_TOGGLE_RA_MANGLE:
case REG_CFA_WINDOW_SAVE:
+ /* We overload both of these operations onto the same DWARF
opcode. */
dwarf2out_frame_debug_cfa_window_save ();
handled_one = true;
break;
This keeps the two reg notes separate within the compiler, but emits the
same dwarf operation during final output. This avoids the need for new
hooks or anything more complicated.
This was my initial thoughts and the patch would be very small as you've
demonstrated. I later moved to this complexer patch as I am thinking it's
better to completely treat notes in reg-notes.def as having generic meaning and
maps them to standard DWARF CFA if there is, otherwise maps them to target
private DWARF CFA through this new hook. This give other targets a chance to
map, for example REG_CFA_TOGGLE_RA_MANGLE, to their architecture DWARF number.
The introduction of new hook looks be very low risk in this stage, the only
painful thing is the header file needs to be reorganized as we need to use some
DWARF type and reg-note type in targhooks.c.
Anyway, if the new hook patch is too heavy, I have attached the the simplified
version which simply defines the new REG_CFA_TOGGLE_RA_MANGLE and maps to same
code of REG_CFA_WINDOW_SAVE.
gcc/
2017-01-17 Jiong Wang <jiong.w...@arm.com>
* reg-notes.def (CFA_TOGGLE_RA_MANGLE): New reg-note.
* combine-stack-adj.c (no_unhandled_cfa): Handle
REG_CFA_TOGGLE_RA_MANGLE.
* dwarf2cfi.c
(dwarf2out_frame_debug): Handle REG_CFA_TOGGLE_RA_MANGLE.
* config/aarch64/aarch64.c (aarch64_expand_prologue): Generates DWARF
info for return address signing.
(aarch64_expand_epilogue): Likewise.
diff --git a/gcc/combine-stack-adj.c b/gcc/combine-stack-adj.c
index 20cd59ad08329e9f4f834bfc01d6f9ccc4485283..9ec14a3e44363f35f6419c38233ce5eebddd3458 100644
--- a/gcc/combine-stack-adj.c
+++ b/gcc/combine-stack-adj.c
@@ -208,6 +208,7 @@ no_unhandled_cfa (rtx_insn *insn)
case REG_CFA_SET_VDRAP:
case REG_CFA_WINDOW_SAVE:
case REG_CFA_FLUSH_QUEUE:
+ case REG_CFA_TOGGLE_RA_MANGLE:
return false;
}
diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c
index 3bcad76b68b6ea7c9d75d150d79c45fb74d6bf0d..6451b08191cf1a44aed502930da8603111f6e8ca 100644
--- a/gcc/config/aarch64/aarch64.c
+++ b/gcc/config/aarch64/aarch64.c
@@ -3553,7 +3553,11 @@ aarch64_expand_prologue (void)
/* Sign return address for functions. */
if (aarch64_return_address_signing_enabled ())
- emit_insn (gen_pacisp ());
+ {
+ insn = emit_insn (gen_pacisp ());
+ add_reg_note (insn, REG_CFA_TOGGLE_RA_MANGLE, const0_rtx);
+ RTX_FRAME_RELATED_P (insn) = 1;
+ }
if (flag_stack_usage_info)
current_function_static_stack_size = frame_size;
@@ -3707,7 +3711,11 @@ aarch64_expand_epilogue (bool for_sibcall)
*/
if (aarch64_return_address_signing_enabled ()
&& (for_sibcall || !TARGET_ARMV8_3 || crtl->calls_eh_return))
- emit_insn (gen_autisp ());
+ {
+ insn = emit_insn (gen_autisp ());
+ add_reg_note (insn, REG_CFA_TOGGLE_RA_MANGLE, const0_rtx);
+ RTX_FRAME_RELATED_P (insn) = 1;
+ }
/* Stack adjustment for exception handler. */
if (crtl->calls_eh_return)
diff --git a/gcc/dwarf2cfi.c b/gcc/dwarf2cfi.c
index 2748e2fa48e4794181496b26df9b51b7e51e7b84..2a527c9fecab091dccb417492e5dbb2ade244be2 100644
--- a/gcc/dwarf2cfi.c
+++ b/gcc/dwarf2cfi.c
@@ -2098,7 +2098,9 @@ dwarf2out_frame_debug (rtx_insn *insn)
handled_one = true;
break;
+ case REG_CFA_TOGGLE_RA_MANGLE:
case REG_CFA_WINDOW_SAVE:
+ /* We overload both of these operations onto the same DWARF opcode. */
dwarf2out_frame_debug_cfa_window_save ();
handled_one = true;
break;
diff --git a/gcc/reg-notes.def b/gcc/reg-notes.def
index ead4a9f58e8621288ee765e029c673640fdf38f4..175da119b6a534b04bd154f2c69dd087afd474ea 100644
--- a/gcc/reg-notes.def
+++ b/gcc/reg-notes.def
@@ -177,6 +177,11 @@ REG_NOTE (CFA_WINDOW_SAVE)
the rest of the compiler as a CALL_INSN. */
REG_NOTE (CFA_FLUSH_QUEUE)
+/* Attached to insns that are RTX_FRAME_RELATED_P, toggling the mangling status
+ of return address. Currently it's only used by AArch64. The argument is
+ ignored. */
+REG_NOTE (CFA_TOGGLE_RA_MANGLE)
+
/* Indicates what exception region an INSN belongs in. This is used
to indicate what region to which a call may throw. REGION 0
indicates that a call cannot throw at all. REGION -1 indicates
