[Patch] Ad PR 56064: Extend fixed_from_double_int input

[Georg-Johann Lay <avr at gjlay dot de>]

This patch solves a problem with VIEW_CONVERT_EXPR folding for fixed_cst and
that use fixed-value.c:fixed_from_double_int.

The patch sign/zero extends the double_int input according to the requested
fixed-point mode.

The patch bootstraps on x86-linux-gnu and passes testsuite on avr-unknown one.

Without this patch, the new test case fails because when a SAmode is
constructed in fold-const.c:native_interpret_fixed(), the MSBs are not set
according to the sign of the value.

However, functions dealing with fixed-point constants use all bits of the
underlying double_int, not only those covered by the mode mask.

Moreover, some sanity checking is added for to the incoming machine mode.

Ok for trunk?

gcc/
	PR tree-optimization/56064
	* fixed-value.c (fixed_from_double_int): Sign/zero extend payload
	bits according to mode.
	* fixed-value.h (fixed_from_double_int)
	(const_fixed_from_double_int): Adjust comments.

gcc/testsuite/
	PR tree-optimization/56064
	* gcc.dg/fixed-point/view-convert-2.c: New test.


Index: fixed-value.c
===================================================================
--- fixed-value.c	(revision 195736)
+++ fixed-value.c	(working copy)
@@ -83,7 +83,7 @@ check_real_for_fixed_mode (REAL_VALUE_TY
 
 
 /* Construct a CONST_FIXED from a bit payload and machine mode MODE.
-   The bits in PAYLOAD are used verbatim.  */
+   The bits in PAYLOAD are sign-extended/zero-extended according to MODE.  */
 
 FIXED_VALUE_TYPE
 fixed_from_double_int (double_int payload, enum machine_mode mode)
@@ -92,7 +92,13 @@ fixed_from_double_int (double_int payloa
 
   gcc_assert (GET_MODE_BITSIZE (mode) <= HOST_BITS_PER_DOUBLE_INT);
 
-  value.data = payload;
+  if (SIGNED_SCALAR_FIXED_POINT_MODE_P (mode))
+    value.data = payload.sext (1 + GET_MODE_IBIT (mode) + GET_MODE_FBIT (mode));
+  else if (UNSIGNED_SCALAR_FIXED_POINT_MODE_P (mode))
+    value.data = payload.zext (GET_MODE_IBIT (mode) + GET_MODE_FBIT (mode));
+  else
+    gcc_unreachable();
+
   value.mode = mode;
 
   return value;
Index: fixed-value.h
===================================================================
--- fixed-value.h	(revision 195736)
+++ fixed-value.h	(working copy)
@@ -50,12 +50,12 @@ extern FIXED_VALUE_TYPE fconst1[MAX_FCON
 extern rtx const_fixed_from_fixed_value (FIXED_VALUE_TYPE, enum machine_mode);
 
 /* Construct a FIXED_VALUE from a bit payload and machine mode MODE.
-   The bits in PAYLOAD are used verbatim.  */
+   The bits in PAYLOAD are sign-extended/zero-extended according to MODE.  */
 extern FIXED_VALUE_TYPE fixed_from_double_int (double_int,
 						     enum machine_mode);
 
 /* Return a CONST_FIXED from a bit payload and machine mode MODE.
-   The bits in PAYLOAD are used verbatim.  */
+   The bits in PAYLOAD are sign-extended/zero-extended according to MODE.  */
 static inline rtx
 const_fixed_from_double_int (double_int payload,
                              enum machine_mode mode)
Index: testsuite/gcc.dg/fixed-point/view-convert-2.c
===================================================================
--- testsuite/gcc.dg/fixed-point/view-convert-2.c	(revision 0)
+++ testsuite/gcc.dg/fixed-point/view-convert-2.c	(revision 0)
@@ -0,0 +1,139 @@
+/* PR tree-optimization/56064 */
+/* { dg-do run } */
+/* { dg-options "-std=gnu99 -O2" } */
+
+extern void abort (void);
+extern void exit (int);
+
+void test_k (void)
+{
+  _Accum a;
+  __INT32_TYPE__ i = -__INT32_MAX__;
+  
+  if (sizeof (a) != sizeof (i))
+    return;
+
+  __builtin_memcpy (&a, &i, sizeof (a));
+
+  if (a >= 0k)
+    abort();
+}
+
+void test_0k (void)
+{
+  _Accum a;
+  __INT32_TYPE__ i = 0;
+  
+  if (sizeof (a) != sizeof (i))
+    return;
+
+  __builtin_memcpy (&a, &i, sizeof (a));
+
+  if (a != 0k)
+    abort();
+}
+
+
+void test_hr (void)
+{
+  short _Fract a;
+  __INT8_TYPE__ i = -__INT8_MAX__;
+
+  if (sizeof (a) != sizeof (i))
+    return;
+
+  __builtin_memcpy (&a, &i, sizeof (a));
+
+  if (a >= 0hr)
+    abort();
+}
+
+void test_0hr (void)
+{
+  short _Fract a;
+  __INT8_TYPE__ i = 0;
+
+  if (sizeof (a) != sizeof (i))
+    return;
+
+  __builtin_memcpy (&a, &i, sizeof (a));
+
+  if (a != 0hr)
+    abort();
+}
+
+
+void test_si (void)
+{
+  _Accum a = __ACCUM_MIN__;
+  __INT32_TYPE__ i;
+
+  if (sizeof (a) != sizeof (i))
+    return;
+
+  __builtin_memcpy (&i, &a, sizeof (i));
+
+  if (i >= 0)
+    abort();
+}
+
+void test_0si (void)
+{
+  _Accum a = 0;
+  __INT32_TYPE__ i;
+
+  if (sizeof (a) != sizeof (i))
+    return;
+
+  __builtin_memcpy (&i, &a, sizeof (i));
+
+  if (i != 0)
+    abort();
+}
+
+
+void test_qi (void)
+{
+  short _Fract a = __SFRACT_MIN__;
+  __INT8_TYPE__ i;
+
+  if (sizeof (a) != sizeof (i))
+    return;
+
+  __builtin_memcpy (&i, &a, sizeof (i));
+
+  if (i >= 0)
+    abort();
+}
+
+void test_0qi (void)
+{
+  short _Fract a = 0hr;
+  __INT8_TYPE__ i;
+
+  if (sizeof (a) != sizeof (i))
+    return;
+
+  __builtin_memcpy (&i, &a, sizeof (i));
+
+  if (i != 0)
+    abort();
+}
+
+
+int main (void)
+{
+  test_hr();
+  test_k();
+  test_qi();
+  test_si();
+
+  test_0hr();
+  test_0k();
+  test_0qi();
+  test_0si();
+
+  exit (0);
+
+  return 0;
+}