[gcc(refs/vendors/ARM/heads/CVE-2023-4039/gcc-9)] aarch64: Add bytes_below_hard_fp to frame info

[gcc(refs/vendors/ARM/heads/CVE-2023-4039/gcc-9)] aarch64: Add bytes_below_hard_fp to frame info

[Richard Sandiford]

https://gcc.gnu.org/g:347487fffa0266d43bf18f1f91878410881f596e

commit 347487fffa0266d43bf18f1f91878410881f596e
Author: Richard Sandiford <richard.sandiford@arm.com>
Date:   Fri Jun 16 16:55:12 2023 +0100

    aarch64: Add bytes_below_hard_fp to frame info
    
    The frame layout code currently hard-codes the assumption that
    the number of bytes below the saved registers is equal to the
    size of the outgoing arguments.  This patch abstracts that
    value into a new field of aarch64_frame.
    
    gcc/
            * config/aarch64/aarch64.h (aarch64_frame::bytes_below_hard_fp): New
            field.
            * config/aarch64/aarch64.c (aarch64_layout_frame): Initialize it,
            and use it instead of crtl->outgoing_args_size.
            (aarch64_get_separate_components): Use bytes_below_hard_fp instead
            of outgoing_args_size.
            (aarch64_process_components): Likewise.

Diff:
---
 gcc/config/aarch64/aarch64.c | 50 ++++++++++++++++++++++++--------------------
 gcc/config/aarch64/aarch64.h |  6 +++++-
 2 files changed, 32 insertions(+), 24 deletions(-)

diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c
index e9dad682738f..25cf10cc4b94 100644
--- a/gcc/config/aarch64/aarch64.c
+++ b/gcc/config/aarch64/aarch64.c
@@ -4684,6 +4684,8 @@ aarch64_layout_frame (void)
 	last_fp_reg = regno;
       }
 
+  cfun->machine->frame.bytes_below_hard_fp = crtl->outgoing_args_size;
+
   if (cfun->machine->frame.emit_frame_chain)
     {
       /* FP and LR are placed in the linkage record.  */
@@ -4751,11 +4753,11 @@ aarch64_layout_frame (void)
 			   STACK_BOUNDARY / BITS_PER_UNIT);
 
   /* Both these values are already aligned.  */
-  gcc_assert (multiple_p (crtl->outgoing_args_size,
+  gcc_assert (multiple_p (cfun->machine->frame.bytes_below_hard_fp,
 			  STACK_BOUNDARY / BITS_PER_UNIT));
   cfun->machine->frame.frame_size
     = (cfun->machine->frame.hard_fp_offset
-       + crtl->outgoing_args_size);
+       + cfun->machine->frame.bytes_below_hard_fp);
 
   cfun->machine->frame.locals_offset = cfun->machine->frame.saved_varargs_size;
 
@@ -4775,23 +4777,23 @@ aarch64_layout_frame (void)
     cfun->machine->frame.initial_adjust = cfun->machine->frame.frame_size;
   else if (cfun->machine->frame.frame_size.is_constant (&const_size)
 	   && const_size < max_push_offset
-	   && known_eq (crtl->outgoing_args_size, 0))
+	   && known_eq (cfun->machine->frame.bytes_below_hard_fp, 0))
     {
-      /* Simple, small frame with no outgoing arguments:
+      /* Simple, small frame with no data below the saved registers.
 	 stp reg1, reg2, [sp, -frame_size]!
 	 stp reg3, reg4, [sp, 16]  */
       cfun->machine->frame.callee_adjust = const_size;
     }
-  else if (known_lt (crtl->outgoing_args_size
+  else if (known_lt (cfun->machine->frame.bytes_below_hard_fp
 		     + cfun->machine->frame.saved_regs_size, 512)
 	   && !(cfun->calls_alloca
 		&& known_lt (cfun->machine->frame.hard_fp_offset,
 			     max_push_offset)))
     {
-      /* Frame with small outgoing arguments:
+      /* Frame with small area below the saved registers:
 	 sub sp, sp, frame_size
-	 stp reg1, reg2, [sp, outgoing_args_size]
-	 stp reg3, reg4, [sp, outgoing_args_size + 16]  */
+	 stp reg1, reg2, [sp, bytes_below_hard_fp]
+	 stp reg3, reg4, [sp, bytes_below_hard_fp + 16]  */
       cfun->machine->frame.initial_adjust = cfun->machine->frame.frame_size;
       cfun->machine->frame.callee_offset
 	= cfun->machine->frame.frame_size - cfun->machine->frame.hard_fp_offset;
@@ -4799,22 +4801,23 @@ aarch64_layout_frame (void)
   else if (cfun->machine->frame.hard_fp_offset.is_constant (&const_fp_offset)
 	   && const_fp_offset < max_push_offset)
     {
-      /* Frame with large outgoing arguments but a small local area:
+      /* Frame with large area below the saved registers, but with a
+	 small area above:
 	 stp reg1, reg2, [sp, -hard_fp_offset]!
 	 stp reg3, reg4, [sp, 16]
-	 sub sp, sp, outgoing_args_size  */
+	 sub sp, sp, bytes_below_hard_fp  */
       cfun->machine->frame.callee_adjust = const_fp_offset;
       cfun->machine->frame.final_adjust
 	= cfun->machine->frame.frame_size - cfun->machine->frame.callee_adjust;
     }
   else
     {
-      /* Frame with large local area and outgoing arguments using frame pointer:
+      /* General case:
 	 sub sp, sp, hard_fp_offset
 	 stp x29, x30, [sp, 0]
 	 add x29, sp, 0
 	 stp reg3, reg4, [sp, 16]
-	 sub sp, sp, outgoing_args_size  */
+	 sub sp, sp, bytes_below_hard_fp  */
       cfun->machine->frame.initial_adjust = cfun->machine->frame.hard_fp_offset;
       cfun->machine->frame.final_adjust
 	= cfun->machine->frame.frame_size - cfun->machine->frame.initial_adjust;
@@ -5243,9 +5246,11 @@ aarch64_get_separate_components (void)
     if (aarch64_register_saved_on_entry (regno))
       {
 	poly_int64 offset = cfun->machine->frame.reg_offset[regno];
+
+	/* Get the offset relative to the register we'll use.  */
 	if (!frame_pointer_needed)
-	  offset += cfun->machine->frame.frame_size
-		    - cfun->machine->frame.hard_fp_offset;
+	  offset += cfun->machine->frame.bytes_below_hard_fp;
+
 	/* Check that we can access the stack slot of the register with one
 	   direct load with no adjustments needed.  */
 	if (offset_12bit_unsigned_scaled_p (DImode, offset))
@@ -5367,8 +5372,8 @@ aarch64_process_components (sbitmap components, bool prologue_p)
       rtx reg = gen_rtx_REG (mode, regno);
       poly_int64 offset = cfun->machine->frame.reg_offset[regno];
       if (!frame_pointer_needed)
-	offset += cfun->machine->frame.frame_size
-		  - cfun->machine->frame.hard_fp_offset;
+	offset += cfun->machine->frame.bytes_below_hard_fp;
+
       rtx addr = plus_constant (Pmode, ptr_reg, offset);
       rtx mem = gen_frame_mem (mode, addr);
 
@@ -5410,8 +5415,7 @@ aarch64_process_components (sbitmap components, bool prologue_p)
       /* REGNO2 can be saved/restored in a pair with REGNO.  */
       rtx reg2 = gen_rtx_REG (mode, regno2);
       if (!frame_pointer_needed)
-	offset2 += cfun->machine->frame.frame_size
-		  - cfun->machine->frame.hard_fp_offset;
+	offset2 += cfun->machine->frame.bytes_below_hard_fp;
       rtx addr2 = plus_constant (Pmode, ptr_reg, offset2);
       rtx mem2 = gen_frame_mem (mode, addr2);
       rtx set2 = prologue_p ? gen_rtx_SET (mem2, reg2)
@@ -5478,10 +5482,10 @@ aarch64_stack_clash_protection_alloca_probe_range (void)
    registers.  If POLY_SIZE is not large enough to require a probe this function
    will only adjust the stack.  When allocating the stack space
    FRAME_RELATED_P is then used to indicate if the allocation is frame related.
-   FINAL_ADJUSTMENT_P indicates whether we are allocating the outgoing
-   arguments.  If we are then we ensure that any allocation larger than the ABI
-   defined buffer needs a probe so that the invariant of having a 1KB buffer is
-   maintained.
+   FINAL_ADJUSTMENT_P indicates whether we are allocating the area below
+   the saved registers.  If we are then we ensure that any allocation
+   larger than the ABI defined buffer needs a probe so that the
+   invariant of having a 1KB buffer is maintained.
 
    We emit barriers after each stack adjustment to prevent optimizations from
    breaking the invariant that we never drop the stack more than a page.  This
@@ -5671,7 +5675,7 @@ aarch64_allocate_and_probe_stack_space (rtx temp1, rtx temp2,
   /* Handle any residuals.  Residuals of at least MIN_PROBE_THRESHOLD have to
      be probed.  This maintains the requirement that each page is probed at
      least once.  For initial probing we probe only if the allocation is
-     more than GUARD_SIZE - buffer, and for the outgoing arguments we probe
+     more than GUARD_SIZE - buffer, and below the saved registers we probe
      if the amount is larger than buffer.  GUARD_SIZE - buffer + buffer ==
      GUARD_SIZE.  This works that for any allocation that is large enough to
      trigger a probe here, we'll have at least one, and if they're not large
diff --git a/gcc/config/aarch64/aarch64.h b/gcc/config/aarch64/aarch64.h
index af0bc3f18817..95831637ba73 100644
--- a/gcc/config/aarch64/aarch64.h
+++ b/gcc/config/aarch64/aarch64.h
@@ -712,9 +712,13 @@ struct GTY (()) aarch64_frame
   HOST_WIDE_INT saved_varargs_size;
 
   /* The size of the saved callee-save int/FP registers.  */
-
   HOST_WIDE_INT saved_regs_size;
 
+  /* The number of bytes between the bottom of the static frame (the bottom
+     of the outgoing arguments) and the hard frame pointer.  This value is
+     always a multiple of STACK_BOUNDARY.  */
+  poly_int64 bytes_below_hard_fp;
+
   /* Offset from the base of the frame (incomming SP) to the
      top of the locals area.  This value is always a multiple of
      STACK_BOUNDARY.  */