[SPARC] Fix PR target/114416

[SPARC] Fix PR target/114416

[Eric Botcazou]

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For the 20th anniversary of https://gcc.gnu.org/gcc-3.4/sparc-abi.html, a new 
calling convention incompatibility with the vendor compiler (and the ABI) has 
been discovered in 64-bit mode, affecting small structures containing arrays 
of floating-point components.  The decision has been made to fix it on Solaris 
only at this point.

Bootstrapped/regtested on SPARC/Solaris 11.4 and SPARC64/Linux by Rainer (many 
thanks again) and applied on the mainline.


2024-04-25  Eric Botcazou  <ebotcazou@adacore.com>

	PR target/114416
	* config/sparc/sparc.h (SUN_V9_ABI_COMPATIBILITY): New macro.
	* config/sparc/sol2.h (SUN_V9_ABI_COMPATIBILITY): Redefine it.
	* config/sparc/sparc.cc (fp_type_for_abi): New predicate.
	(traverse_record_type): Use it to spot floating-point types.
	(compute_fp_layout): Also deal with array types.


2024-04-25  Eric Botcazou  <ebotcazou@adacore.com>

	* gcc.target/sparc/small-struct-1.c: New test.

-- 
Eric Botcazou

[-- Attachment #2: pr114416.diff --]
[-- Type: text/x-patch, Size: 2594 bytes --]

diff --git a/gcc/config/sparc/sol2.h b/gcc/config/sparc/sol2.h
index e849af9038b..552f58b2cc8 100644
--- a/gcc/config/sparc/sol2.h
+++ b/gcc/config/sparc/sol2.h
@@ -456,3 +456,6 @@ extern const char *host_detect_local_cpu (int argc, const char **argv);
 
 #undef SPARC_LOW_FE_EXCEPT_VALUES
 #define SPARC_LOW_FE_EXCEPT_VALUES 1
+
+#undef SUN_V9_ABI_COMPATIBILITY
+#define SUN_V9_ABI_COMPATIBILITY 1
diff --git a/gcc/config/sparc/sparc.cc b/gcc/config/sparc/sparc.cc
index 30fa4474bbd..8a5f76c8885 100644
--- a/gcc/config/sparc/sparc.cc
+++ b/gcc/config/sparc/sparc.cc
@@ -6782,6 +6782,22 @@ sparc_pass_by_reference (cumulative_args_t, const function_arg_info &arg)
 	    || GET_MODE_SIZE (mode) > 16);
 }
 
+/* Return true if TYPE is considered as a floating-point type by the ABI.  */
+
+static bool
+fp_type_for_abi (const_tree type)
+{
+  /* This is the original GCC implementation.  */
+  if (FLOAT_TYPE_P (type) || VECTOR_TYPE_P (type))
+    return true;
+
+  /* This has been introduced in GCC 14 to match the vendor compiler.  */
+  if (SUN_V9_ABI_COMPATIBILITY && TREE_CODE (type) == ARRAY_TYPE)
+    return fp_type_for_abi (TREE_TYPE (type));
+
+  return false;
+}
+
 /* Traverse the record TYPE recursively and call FUNC on its fields.
    NAMED is true if this is for a named parameter.  DATA is passed
    to FUNC for each field.  OFFSET is the starting position and
@@ -6820,8 +6836,7 @@ traverse_record_type (const_tree type, bool named, T *data,
 					 packed);
 	else
 	  {
-	    const bool fp_type
-	      = FLOAT_TYPE_P (field_type) || VECTOR_TYPE_P (field_type);
+	    const bool fp_type = fp_type_for_abi (field_type);
 	    Func (field, bitpos, fp_type && named && !packed && TARGET_FPU,
 		  data);
 	  }
@@ -7072,6 +7087,13 @@ compute_fp_layout (const_tree field, int bitpos, assign_data_t *data,
       mode = TYPE_MODE (TREE_TYPE (TREE_TYPE (field)));
       nregs = 2;
     }
+  else if (TREE_CODE (TREE_TYPE (field)) == ARRAY_TYPE)
+    {
+      tree elt_type = strip_array_types (TREE_TYPE (field));
+      mode = TYPE_MODE (elt_type);
+      nregs
+	= int_size_in_bytes (TREE_TYPE (field)) / int_size_in_bytes (elt_type);
+    }
   else
     nregs = 1;
 
diff --git a/gcc/config/sparc/sparc.h b/gcc/config/sparc/sparc.h
index fb074808d30..232ecb30ddc 100644
--- a/gcc/config/sparc/sparc.h
+++ b/gcc/config/sparc/sparc.h
@@ -1700,3 +1700,6 @@ extern int sparc_indent_opcode;
 #define SPARC_LOW_FE_EXCEPT_VALUES 0
 
 #define TARGET_SUPPORTS_WIDE_INT 1
+
+/* Define this to 1 to accept ABI changes to match the vendor compiler.  */
+#define SUN_V9_ABI_COMPATIBILITY 0

[-- Attachment #3: small-struct-1.c --]
[-- Type: text/x-csrc, Size: 640 bytes --]

/* PR target/114416 */
/* Reported by Rainer Orth <ro@gcc.gnu.org> */

/* { dg-do compile } */
/* { dg-options "-O" } */
/* { dg-require-effective-target lp64 } */

struct vec2
{
  double x[2];
};

struct vec2x
{
  double x;
  double y;
};

struct vec2 sum2 (double val)
{
  struct vec2 v;
  v.x[0] = val;
  v.x[1] = val;
  return v;
}

struct vec2x sum2x (double val)
{
  struct vec2x v;
  v.x = val;
  v.y = val;
  return v;
}

double get2 (struct vec2 v)
{
  return v.x[0] + v.x[1];
}

double get2x (struct vec2x v)
{
  return v.x + v.y;
}

/* { dg-final { scan-assembler-not "ldx" } } */
/* { dg-final { scan-assembler-not "stx" } } */

Re: [SPARC] Fix PR target/114416

[Eric Botcazou]

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> For the 20th anniversary of https://gcc.gnu.org/gcc-3.4/sparc-abi.html, a
> new calling convention incompatibility with the vendor compiler (and the
> ABI) has been discovered in 64-bit mode, affecting small structures
> containing arrays of floating-point components.  The decision has been made
> to fix it on Solaris only at this point.

Documented by the attached patch, validated with W3C's Validator and applied.

-- 
Eric Botcazou

[-- Attachment #2: p.diff --]
[-- Type: text/x-patch, Size: 973 bytes --]

diff --git a/htdocs/gcc-14/changes.html b/htdocs/gcc-14/changes.html
index f0f0efe0..83b1016c 100644
--- a/htdocs/gcc-14/changes.html
+++ b/htdocs/gcc-14/changes.html
@@ -136,7 +136,7 @@ a work-in-progress.</p>
 	    int foo (int n)
 	    {
 	      int res = 0;
-	      for (int i = 0; i < n; i++)
+	      for (int i = 0; i &lt; n; i++)
 		{
 		   y[i] = x[i] * 2;
 		   res += x[i] + y[i];
@@ -1212,7 +1212,17 @@ __asm (".global __flmap_lock"  "\n\t"
 
 <!-- <h3 id="sh">SH</h3> -->
 
-<!-- <h3 id="sparc">SPARC</h3> -->
+<h3 id="sparc">SPARC</h3>
+
+<ul>
+  <li>
+    The implementation of calling conventions for small structures containing
+    arrays of floating-point components has been changed in 64-bit mode for
+    the Solaris port to match the implementation of the vendor compiler (and
+    the ABI). As a result, the code generated will not be binary compatible
+    with earlier releases in these cases.
+  </li>
+</ul>
 
 <!-- <h3 id="Tile">Tile</h3> -->