[gcc r13-4981] Revert "Compute a table of DWARF register sizes at compile"

[gcc r13-4981] Revert "Compute a table of DWARF register sizes at compile"

[Florian Weimer]

https://gcc.gnu.org/g:455acc43518744b89d6a795bbba5045bd228060b

commit r13-4981-g455acc43518744b89d6a795bbba5045bd228060b
Author: Florian Weimer <fweimer@redhat.com>
Date:   Tue Jan 3 16:47:31 2023 +0100

    Revert "Compute a table of DWARF register sizes at compile"
    
    This reverts commit 3b6cac2b44b384cd2091eaeaebeb3478c253a25d.

Diff:
---
 gcc/config/msp430/msp430.cc | 11 +++++-
 gcc/config/rs6000/rs6000.cc | 14 ++++++-
 gcc/doc/tm.texi             |  7 ++--
 gcc/dwarf2cfi.cc            | 93 +++++++++++++++++++++++----------------------
 gcc/target.def              |  8 ++--
 5 files changed, 75 insertions(+), 58 deletions(-)

diff --git a/gcc/config/msp430/msp430.cc b/gcc/config/msp430/msp430.cc
index dbea8d7f50f..6c15780a2b6 100644
--- a/gcc/config/msp430/msp430.cc
+++ b/gcc/config/msp430/msp430.cc
@@ -3202,9 +3202,11 @@ msp430_expand_eh_return (rtx eh_handler)
 #undef  TARGET_INIT_DWARF_REG_SIZES_EXTRA
 #define TARGET_INIT_DWARF_REG_SIZES_EXTRA msp430_init_dwarf_reg_sizes_extra
 void
-msp430_init_dwarf_reg_sizes_extra (poly_uint16 *sizes)
+msp430_init_dwarf_reg_sizes_extra (tree address)
 {
   int i;
+  rtx addr = expand_normal (address);
+  rtx mem = gen_rtx_MEM (BLKmode, addr);
 
   /* This needs to match msp430_unwind_word_mode (above).  */
   if (!msp430x)
@@ -3216,7 +3218,12 @@ msp430_init_dwarf_reg_sizes_extra (poly_uint16 *sizes)
       unsigned int rnum = DWARF2_FRAME_REG_OUT (dnum, 1);
 
       if (rnum < DWARF_FRAME_REGISTERS)
-	sizes[rnum] = 4;
+	{
+	  HOST_WIDE_INT offset = rnum * GET_MODE_SIZE (QImode);
+
+	  emit_move_insn (adjust_address (mem, QImode, offset),
+			  gen_int_mode (4, QImode));
+	}
     }
 }
 
diff --git a/gcc/config/rs6000/rs6000.cc b/gcc/config/rs6000/rs6000.cc
index 875684a3895..6ac3adcec6b 100644
--- a/gcc/config/rs6000/rs6000.cc
+++ b/gcc/config/rs6000/rs6000.cc
@@ -23860,17 +23860,27 @@ rs6000_initial_elimination_offset (int from, int to)
 /* Fill in sizes of registers used by unwinder.  */
 
 static void
-rs6000_init_dwarf_reg_sizes_extra (poly_uint16 *sizes)
+rs6000_init_dwarf_reg_sizes_extra (tree address)
 {
   if (TARGET_MACHO && ! TARGET_ALTIVEC)
     {
       int i;
+      machine_mode mode = TYPE_MODE (char_type_node);
+      rtx addr = expand_expr (address, NULL_RTX, VOIDmode, EXPAND_NORMAL);
+      rtx mem = gen_rtx_MEM (BLKmode, addr);
+      rtx value = gen_int_mode (16, mode);
 
       /* On Darwin, libgcc may be built to run on both G3 and G4/5.
 	 The unwinder still needs to know the size of Altivec registers.  */
 
       for (i = FIRST_ALTIVEC_REGNO; i < LAST_ALTIVEC_REGNO+1; i++)
-	sizes[i] = 16;
+	{
+	  int column = DWARF_REG_TO_UNWIND_COLUMN
+		(DWARF2_FRAME_REG_OUT (DWARF_FRAME_REGNUM (i), true));
+	  HOST_WIDE_INT offset = column * GET_MODE_SIZE (mode);
+
+	  emit_move_insn (adjust_address (mem, mode, offset), value);
+	}
     }
 }
 
diff --git a/gcc/doc/tm.texi b/gcc/doc/tm.texi
index b6d7900f212..8fe49c2ba3d 100644
--- a/gcc/doc/tm.texi
+++ b/gcc/doc/tm.texi
@@ -9840,14 +9840,13 @@ used to return a smaller mode than the raw mode to prevent call
 clobbered parts of a register altering the frame register size
 @end deftypefn
 
-@deftypefn {Target Hook} void TARGET_INIT_DWARF_REG_SIZES_EXTRA (poly_uint16 *@var{sizes})
+@deftypefn {Target Hook} void TARGET_INIT_DWARF_REG_SIZES_EXTRA (tree @var{address})
 If some registers are represented in Dwarf-2 unwind information in
 multiple pieces, define this hook to fill in information about the
 sizes of those pieces in the table used by the unwinder at runtime.
-It will be called by @code{generate_dwarf_reg_sizes} after
+It will be called by @code{expand_builtin_init_dwarf_reg_sizes} after
 filling in a single size corresponding to each hard register;
-@var{sizes} is the address of the table.  It will contain
-@code{DWARF_FRAME_REGISTERS} elements when this hook is called.
+@var{address} is the address of the table.
 @end deftypefn
 
 @deftypefn {Target Hook} bool TARGET_ASM_TTYPE (rtx @var{sym})
diff --git a/gcc/dwarf2cfi.cc b/gcc/dwarf2cfi.cc
index 4d2bd869a4b..1c70bd83f28 100644
--- a/gcc/dwarf2cfi.cc
+++ b/gcc/dwarf2cfi.cc
@@ -36,7 +36,7 @@ along with GCC; see the file COPYING3.  If not see
 
 #include "except.h"		/* expand_builtin_dwarf_sp_column */
 #include "profile-count.h"	/* For expr.h */
-#include "expr.h"		/* expand_normal, emit_move_insn */
+#include "expr.h"		/* init_return_column_size */
 #include "output.h"		/* asm_out_file */
 #include "debug.h"		/* dwarf2out_do_frame, dwarf2out_do_cfi_asm */
 #include "flags.h"		/* dwarf_debuginfo_p */
@@ -241,6 +241,18 @@ expand_builtin_dwarf_sp_column (void)
   return GEN_INT (DWARF2_FRAME_REG_OUT (dwarf_regnum, 1));
 }
 
+/* MEM is a memory reference for the register size table, each element of
+   which has mode MODE.  Initialize column C as a return address column.  */
+
+static void
+init_return_column_size (scalar_int_mode mode, rtx mem, unsigned int c)
+{
+  HOST_WIDE_INT offset = c * GET_MODE_SIZE (mode);
+  HOST_WIDE_INT size = GET_MODE_SIZE (Pmode);
+  emit_move_insn (adjust_address (mem, mode, offset),
+		  gen_int_mode (size, mode));
+}
+
 /* Datastructure used by expand_builtin_init_dwarf_reg_sizes and
    init_one_dwarf_reg_size to communicate on what has been done by the
    latter.  */
@@ -262,14 +274,17 @@ struct init_one_dwarf_reg_state
    use for the size entry to initialize, and INIT_STATE is the communication
    datastructure conveying what we're doing to our caller.  */
 
-static void
-init_one_dwarf_reg_size (int regno, machine_mode regmode,
-			 poly_uint16 *table,
-			 init_one_dwarf_reg_state *init_state)
+static
+void init_one_dwarf_reg_size (int regno, machine_mode regmode,
+			      rtx table, machine_mode slotmode,
+			      init_one_dwarf_reg_state *init_state)
 {
   const unsigned int dnum = DWARF_FRAME_REGNUM (regno);
   const unsigned int rnum = DWARF2_FRAME_REG_OUT (dnum, 1);
   const unsigned int dcol = DWARF_REG_TO_UNWIND_COLUMN (rnum);
+  
+  poly_int64 slotoffset = dcol * GET_MODE_SIZE (slotmode);
+  poly_int64 regsize = GET_MODE_SIZE (regmode);
 
   init_state->processed_regno[regno] = true;
 
@@ -283,22 +298,34 @@ init_one_dwarf_reg_size (int regno, machine_mode regmode,
       init_state->wrote_return_column = true;
     }
 
-  table[dcol] = GET_MODE_SIZE (regmode);
+  /* ??? When is this true?  Should it be a test based on DCOL instead?  */
+  if (maybe_lt (slotoffset, 0))
+    return;
+
+  emit_move_insn (adjust_address (table, slotmode, slotoffset),
+		  gen_int_mode (regsize, slotmode));
 }
 
-/* Fill SIZES with size information for each DWARF register. */
+/* Generate code to initialize the dwarf register size table located
+   at the provided ADDRESS.  */
 
-static void
-generate_dwarf_reg_sizes (poly_uint16 *sizes)
+void
+expand_builtin_init_dwarf_reg_sizes (tree address)
 {
-  for (unsigned int i = 0; i < DWARF_FRAME_REGISTERS; i++)
-    sizes[i] = poly_uint16{};
+  unsigned int i;
+  scalar_int_mode mode = SCALAR_INT_TYPE_MODE (char_type_node);
+  rtx addr = expand_normal (address);
+  rtx mem = gen_rtx_MEM (BLKmode, addr);
+
+  init_one_dwarf_reg_state init_state;
 
-  init_one_dwarf_reg_state init_state{};
   memset ((char *)&init_state, 0, sizeof (init_state));
 
-  for (unsigned int i = 0; i < FIRST_PSEUDO_REGISTER; i++)
+  for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
     {
+      machine_mode save_mode;
+      rtx span;
+
       /* No point in processing a register multiple times.  This could happen
 	 with register spans, e.g. when a reg is first processed as a piece of
 	 a span, then as a register on its own later on.  */
@@ -306,11 +333,11 @@ generate_dwarf_reg_sizes (poly_uint16 *sizes)
       if (init_state.processed_regno[i])
 	continue;
 
-      machine_mode save_mode = targetm.dwarf_frame_reg_mode (i);
-      rtx span = targetm.dwarf_register_span (gen_rtx_REG (save_mode, i));
+      save_mode = targetm.dwarf_frame_reg_mode (i);
+      span = targetm.dwarf_register_span (gen_rtx_REG (save_mode, i));
 
       if (!span)
-	init_one_dwarf_reg_size (i, save_mode, sizes, &init_state);
+	init_one_dwarf_reg_size (i, save_mode, mem, mode, &init_state);
       else
 	{
 	  for (int si = 0; si < XVECLEN (span, 0); si++)
@@ -318,45 +345,19 @@ generate_dwarf_reg_sizes (poly_uint16 *sizes)
 	      rtx reg = XVECEXP (span, 0, si);
 
 	      init_one_dwarf_reg_size
-		(REGNO (reg), GET_MODE (reg), sizes, &init_state);
+		(REGNO (reg), GET_MODE (reg), mem, mode, &init_state);
 	    }
 	}
     }
 
   if (!init_state.wrote_return_column)
-    sizes[DWARF_FRAME_RETURN_COLUMN] = GET_MODE_SIZE (Pmode);
+    init_return_column_size (mode, mem, DWARF_FRAME_RETURN_COLUMN);
 
 #ifdef DWARF_ALT_FRAME_RETURN_COLUMN
-  sizes[DWARF_ALT_FRAME_RETURN_COLUMN] = GET_MODE_SIZE (Pmode);
+  init_return_column_size (mode, mem, DWARF_ALT_FRAME_RETURN_COLUMN);
 #endif
 
-  if (targetm.init_dwarf_reg_sizes_extra != nullptr)
-    targetm.init_dwarf_reg_sizes_extra (sizes);
-}
-
-/* Generate code to initialize the dwarf register size table located
-   at the provided ADDRESS.  */
-
-void
-expand_builtin_init_dwarf_reg_sizes (tree address)
-{
-  poly_uint16 *sizes = XALLOCAVEC (poly_uint16, DWARF_FRAME_REGISTERS);
-  generate_dwarf_reg_sizes (sizes);
-
-  scalar_int_mode mode = SCALAR_INT_TYPE_MODE (char_type_node);
-  rtx addr = expand_normal (address);
-  rtx mem = gen_rtx_MEM (BLKmode, addr);
-  for (unsigned int i = 0; i < DWARF_FRAME_REGISTERS; ++i)
-    {
-      unsigned short value;
-      if (sizes[i].is_constant (&value) && value == 0)
-	/* No need to set the value to zero again.  */
-	continue;
-
-      HOST_WIDE_INT offset = i * GET_MODE_SIZE (mode);
-      emit_move_insn (adjust_address (mem, mode, offset),
-		      gen_int_mode (sizes[i], mode));
-    }
+  targetm.init_dwarf_reg_sizes_extra (address);
 }
 
 \f
diff --git a/gcc/target.def b/gcc/target.def
index da5dd31d7a4..db8af0cbe81 100644
--- a/gcc/target.def
+++ b/gcc/target.def
@@ -4039,11 +4039,11 @@ DEFHOOK
  "If some registers are represented in Dwarf-2 unwind information in\n\
 multiple pieces, define this hook to fill in information about the\n\
 sizes of those pieces in the table used by the unwinder at runtime.\n\
-It will be called by @code{generate_dwarf_reg_sizes} after\n\
+It will be called by @code{expand_builtin_init_dwarf_reg_sizes} after\n\
 filling in a single size corresponding to each hard register;\n\
-@var{sizes} is the address of the table.  It will contain\n\
-@code{DWARF_FRAME_REGISTERS} elements when this hook is called.",
- void, (poly_uint16 *sizes), nullptr)
+@var{address} is the address of the table.",
+ void, (tree address),
+ hook_void_tree)
 
 /* Fetch the fixed register(s) which hold condition codes, for
    targets where it makes sense to look for duplicate assignments to