From 50143b85bd90a2e06c0dd192a966574a3279c463 Mon Sep 17 00:00:00 2001
From: Eric Botcazou <ebotcazou@adacore.com>
Date: Tue, 23 May 2023 10:15:35 +0200
Subject: [PATCH] Fix handling of non-integral bit-fields in
 native_encode_initializer

The encoder for CONSTRUCTORs assumes that all bit-fields (DECL_BIT_FIELD)
have integral types, but that's not the case in Ada where they may have
pretty much any type, resulting in a wrong encoding for them

gcc/
	* fold-const.cc (native_encode_initializer) <CONSTRUCTOR>: Apply the
	specific treatment for bit-fields only if they have an integral type
	and filter out non-integral bit-fields that do not start and end on
	a byte boundary.

gcc/testsuite/
	* gnat.dg/opt101.adb: New test.
	* gnat.dg/opt101_pkg.ads: New helper.
---
 gcc/fold-const.cc                    | 27 +++++++++++++++++----------
 gcc/testsuite/gnat.dg/opt101.adb     | 23 +++++++++++++++++++++++
 gcc/testsuite/gnat.dg/opt101_pkg.ads | 26 ++++++++++++++++++++++++++
 3 files changed, 66 insertions(+), 10 deletions(-)
 create mode 100644 gcc/testsuite/gnat.dg/opt101.adb
 create mode 100644 gcc/testsuite/gnat.dg/opt101_pkg.ads

diff --git a/gcc/fold-const.cc b/gcc/fold-const.cc
index 25466e97220..57521501fff 100644
--- a/gcc/fold-const.cc
+++ b/gcc/fold-const.cc
@@ -8360,20 +8360,26 @@ native_encode_initializer (tree init, unsigned char *ptr, int len,
 	      if (fieldsize == 0)
 		continue;
 
+	      /* Prepare to deal with integral bit-fields and filter out other
+		 bit-fields that do not start and end on a byte boundary.  */
 	      if (DECL_BIT_FIELD (field))
 		{
 		  if (!tree_fits_uhwi_p (DECL_FIELD_BIT_OFFSET (field)))
 		    return 0;
-		  fieldsize = TYPE_PRECISION (TREE_TYPE (field));
 		  bpos = tree_to_uhwi (DECL_FIELD_BIT_OFFSET (field));
-		  if (bpos % BITS_PER_UNIT)
-		    bpos %= BITS_PER_UNIT;
-		  else
-		    bpos = 0;
-		  fieldsize += bpos;
-		  epos = fieldsize % BITS_PER_UNIT;
-		  fieldsize += BITS_PER_UNIT - 1;
-		  fieldsize /= BITS_PER_UNIT;
+		  if (INTEGRAL_TYPE_P (TREE_TYPE (field)))
+		    {
+		      bpos %= BITS_PER_UNIT;
+		      fieldsize = TYPE_PRECISION (TREE_TYPE (field)) + bpos;
+		      epos = fieldsize % BITS_PER_UNIT;
+		      fieldsize += BITS_PER_UNIT - 1;
+		      fieldsize /= BITS_PER_UNIT;
+		    }
+		  else if (bpos % BITS_PER_UNIT
+			   || DECL_SIZE (field) == NULL_TREE
+			   || !tree_fits_shwi_p (DECL_SIZE (field))
+			   || tree_to_shwi (DECL_SIZE (field)) % BITS_PER_UNIT)
+		    return 0;
 		}
 
 	      if (off != -1 && pos + fieldsize <= off)
@@ -8382,7 +8388,8 @@ native_encode_initializer (tree init, unsigned char *ptr, int len,
 	      if (val == NULL_TREE)
 		continue;
 
-	      if (DECL_BIT_FIELD (field))
+	      if (DECL_BIT_FIELD (field)
+		  && INTEGRAL_TYPE_P (TREE_TYPE (field)))
 		{
 		  /* FIXME: Handle PDP endian.  */
 		  if (BYTES_BIG_ENDIAN != WORDS_BIG_ENDIAN)
diff --git a/gcc/testsuite/gnat.dg/opt101.adb b/gcc/testsuite/gnat.dg/opt101.adb
new file mode 100644
index 00000000000..68773bbad40
--- /dev/null
+++ b/gcc/testsuite/gnat.dg/opt101.adb
@@ -0,0 +1,23 @@
+-- { dg-do run }
+-- { dg-options "-O" }
+
+pragma Optimize_Alignment (Space);
+
+with Opt101_Pkg; use Opt101_Pkg;
+
+procedure Opt101 is
+
+  C1 : Cont1;
+  C2 : Cont2;
+
+begin
+  C1 := ((1234, 1, 2), 1, 2);
+  if C1.R.I1 /= 1 or C1.I2 /= 2 then
+    raise Program_Error;
+  end if;
+
+  C2 := (1, (1234, 1, 2), 2);
+  if C2.R.I1 /= 1 or C2.I2 /= 2 then
+    raise Program_Error;
+  end if;
+end;
diff --git a/gcc/testsuite/gnat.dg/opt101_pkg.ads b/gcc/testsuite/gnat.dg/opt101_pkg.ads
new file mode 100644
index 00000000000..0c843dfe335
--- /dev/null
+++ b/gcc/testsuite/gnat.dg/opt101_pkg.ads
@@ -0,0 +1,26 @@
+package Opt101_Pkg is
+
+  type Int is mod 16;
+
+  type Rec is record
+    S : Short_Integer;
+    I1, I2 : Int;
+  end record;
+  pragma Pack (Rec);
+  for Rec'Alignment use 4;
+
+  type Cont1 is record
+    R : Rec;
+    I1, I2 : Int;
+  end record;
+  pragma Pack (Cont1);
+
+  type Cont2 is record
+    I1 : Int;
+    R  : Rec;
+    I2 : Int;
+  end record;
+  pragma Pack (Cont2);
+  pragma No_Component_Reordering (Cont2);
+
+end Opt101_Pkg;
-- 
2.11.4.GIT