[patch, libfortran] [patch, fortran] Fix PR 79956, part two, attempt 2

[patch, libfortran] [patch, fortran] Fix PR 79956, part two, attempt 2

[Thomas Koenig]

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Hello world,

Following Richard's suggestion, I have implemented the GFC_ASSERT macro
and used it to (hopefully) silence the ominous warning and allow
further optimization.

OK for trunk?

Regards

	Thomas

2017-03-12  Thomas Koenig  <tkoenig@gcc.gnu.org>

         PR libfortran/79956
         * libgfortran.h (GFC_ASSERT):  New macro.
         * m4/reshape.m4 (reshape_'rtype_ccode`):  Use GFC_ASSERT
         to specify that sdim > 0.
         * intrinsic/reshape_generic.c (reshape_internal):  Likweise.
         * generated/reshape_c10.c: Regenerated.
         * generated/reshape_c16.c: Regenerated.
         * generated/reshape_c4.c: Regenerated.
         * generated/reshape_c8.c: Regenerated.
         * generated/reshape_i16.c: Regenerated.
         * generated/reshape_i4.c: Regenerated.
         * generated/reshape_i8.c: Regenerated.
         * generated/reshape_r10.c: Regenerated.
         * generated/reshape_r16.c: Regenerated.
         * generated/reshape_r4.c: Regenerated.
         * generated/reshape_r8.c: Regenerated.

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Index: generated/reshape_c10.c
===================================================================
--- generated/reshape_c10.c	(Revision 245760)
+++ generated/reshape_c10.c	(Arbeitskopie)
@@ -232,6 +232,11 @@ reshape_c10 (gfc_array_c10 * const restrict ret,
     }
 
   sdim = GFC_DESCRIPTOR_RANK (source);
+
+  /* sdim is always > 0; this lets the compiler optimize more and
+   avoids a warning.  */
+  GFC_ASSERT(sdim>0);
+
   ssize = 1;
   sempty = 0;
   for (n = 0; n < sdim; n++)
Index: generated/reshape_c16.c
===================================================================
--- generated/reshape_c16.c	(Revision 245760)
+++ generated/reshape_c16.c	(Arbeitskopie)
@@ -232,6 +232,11 @@ reshape_c16 (gfc_array_c16 * const restrict ret,
     }
 
   sdim = GFC_DESCRIPTOR_RANK (source);
+
+  /* sdim is always > 0; this lets the compiler optimize more and
+   avoids a warning.  */
+  GFC_ASSERT(sdim>0);
+
   ssize = 1;
   sempty = 0;
   for (n = 0; n < sdim; n++)
Index: generated/reshape_c4.c
===================================================================
--- generated/reshape_c4.c	(Revision 245760)
+++ generated/reshape_c4.c	(Arbeitskopie)
@@ -232,6 +232,11 @@ reshape_c4 (gfc_array_c4 * const restrict ret,
     }
 
   sdim = GFC_DESCRIPTOR_RANK (source);
+
+  /* sdim is always > 0; this lets the compiler optimize more and
+   avoids a warning.  */
+  GFC_ASSERT(sdim>0);
+
   ssize = 1;
   sempty = 0;
   for (n = 0; n < sdim; n++)
Index: generated/reshape_c8.c
===================================================================
--- generated/reshape_c8.c	(Revision 245760)
+++ generated/reshape_c8.c	(Arbeitskopie)
@@ -232,6 +232,11 @@ reshape_c8 (gfc_array_c8 * const restrict ret,
     }
 
   sdim = GFC_DESCRIPTOR_RANK (source);
+
+  /* sdim is always > 0; this lets the compiler optimize more and
+   avoids a warning.  */
+  GFC_ASSERT(sdim>0);
+
   ssize = 1;
   sempty = 0;
   for (n = 0; n < sdim; n++)
Index: generated/reshape_i16.c
===================================================================
--- generated/reshape_i16.c	(Revision 245760)
+++ generated/reshape_i16.c	(Arbeitskopie)
@@ -232,6 +232,11 @@ reshape_16 (gfc_array_i16 * const restrict ret,
     }
 
   sdim = GFC_DESCRIPTOR_RANK (source);
+
+  /* sdim is always > 0; this lets the compiler optimize more and
+   avoids a warning.  */
+  GFC_ASSERT(sdim>0);
+
   ssize = 1;
   sempty = 0;
   for (n = 0; n < sdim; n++)
Index: generated/reshape_i4.c
===================================================================
--- generated/reshape_i4.c	(Revision 245760)
+++ generated/reshape_i4.c	(Arbeitskopie)
@@ -232,6 +232,11 @@ reshape_4 (gfc_array_i4 * const restrict ret,
     }
 
   sdim = GFC_DESCRIPTOR_RANK (source);
+
+  /* sdim is always > 0; this lets the compiler optimize more and
+   avoids a warning.  */
+  GFC_ASSERT(sdim>0);
+
   ssize = 1;
   sempty = 0;
   for (n = 0; n < sdim; n++)
Index: generated/reshape_i8.c
===================================================================
--- generated/reshape_i8.c	(Revision 245760)
+++ generated/reshape_i8.c	(Arbeitskopie)
@@ -232,6 +232,11 @@ reshape_8 (gfc_array_i8 * const restrict ret,
     }
 
   sdim = GFC_DESCRIPTOR_RANK (source);
+
+  /* sdim is always > 0; this lets the compiler optimize more and
+   avoids a warning.  */
+  GFC_ASSERT(sdim>0);
+
   ssize = 1;
   sempty = 0;
   for (n = 0; n < sdim; n++)
Index: generated/reshape_r10.c
===================================================================
--- generated/reshape_r10.c	(Revision 245760)
+++ generated/reshape_r10.c	(Arbeitskopie)
@@ -232,6 +232,11 @@ reshape_r10 (gfc_array_r10 * const restrict ret,
     }
 
   sdim = GFC_DESCRIPTOR_RANK (source);
+
+  /* sdim is always > 0; this lets the compiler optimize more and
+   avoids a warning.  */
+  GFC_ASSERT(sdim>0);
+
   ssize = 1;
   sempty = 0;
   for (n = 0; n < sdim; n++)
Index: generated/reshape_r16.c
===================================================================
--- generated/reshape_r16.c	(Revision 245760)
+++ generated/reshape_r16.c	(Arbeitskopie)
@@ -232,6 +232,11 @@ reshape_r16 (gfc_array_r16 * const restrict ret,
     }
 
   sdim = GFC_DESCRIPTOR_RANK (source);
+
+  /* sdim is always > 0; this lets the compiler optimize more and
+   avoids a warning.  */
+  GFC_ASSERT(sdim>0);
+
   ssize = 1;
   sempty = 0;
   for (n = 0; n < sdim; n++)
Index: generated/reshape_r4.c
===================================================================
--- generated/reshape_r4.c	(Revision 245760)
+++ generated/reshape_r4.c	(Arbeitskopie)
@@ -232,6 +232,11 @@ reshape_r4 (gfc_array_r4 * const restrict ret,
     }
 
   sdim = GFC_DESCRIPTOR_RANK (source);
+
+  /* sdim is always > 0; this lets the compiler optimize more and
+   avoids a warning.  */
+  GFC_ASSERT(sdim>0);
+
   ssize = 1;
   sempty = 0;
   for (n = 0; n < sdim; n++)
Index: generated/reshape_r8.c
===================================================================
--- generated/reshape_r8.c	(Revision 245760)
+++ generated/reshape_r8.c	(Arbeitskopie)
@@ -232,6 +232,11 @@ reshape_r8 (gfc_array_r8 * const restrict ret,
     }
 
   sdim = GFC_DESCRIPTOR_RANK (source);
+
+  /* sdim is always > 0; this lets the compiler optimize more and
+   avoids a warning.  */
+  GFC_ASSERT(sdim>0);
+
   ssize = 1;
   sempty = 0;
   for (n = 0; n < sdim; n++)
Index: intrinsics/reshape_generic.c
===================================================================
--- intrinsics/reshape_generic.c	(Revision 245760)
+++ intrinsics/reshape_generic.c	(Arbeitskopie)
@@ -158,6 +158,10 @@ reshape_internal (parray *ret, parray *source, sha
 
       source_extent = 1;
       sdim = GFC_DESCRIPTOR_RANK (source);
+      /* sdim is always > 0; this lets the compiler optimize more and
+         avoids a warning.  */
+      GFC_ASSERT(sdim>0);
+
       for (n = 0; n < sdim; n++)
 	{
 	  index_type se;
Index: libgfortran.h
===================================================================
--- libgfortran.h	(Revision 245760)
+++ libgfortran.h	(Arbeitskopie)
@@ -111,7 +111,12 @@ typedef off_t gfc_offset;
 #define likely(x)       __builtin_expect(!!(x), 1)
 #define unlikely(x)     __builtin_expect(!!(x), 0)
 
+/* This macro can be used to annotate conditions which we know to
+   be true, so that the compiler can optimize based on the condition.  */
 
+#define GFC_ASSERT(EXPR)                                                \
+  ((void)(__builtin_expect (!(EXPR), 0) ? __builtin_unreachable (), 0 : 0))
+
 /* Make sure we have ptrdiff_t. */
 #ifndef HAVE_PTRDIFF_T
 typedef intptr_t ptrdiff_t;
Index: m4/reshape.m4
===================================================================
--- m4/reshape.m4	(Revision 245760)
+++ m4/reshape.m4	(Arbeitskopie)
@@ -236,6 +236,11 @@ reshape_'rtype_ccode` ('rtype` * const restrict re
     }
 
   sdim = GFC_DESCRIPTOR_RANK (source);
+
+  /* sdim is always > 0; this lets the compiler optimize more and
+   avoids a warning.  */
+  GFC_ASSERT(sdim>0);
+
   ssize = 1;
   sempty = 0;
   for (n = 0; n < sdim; n++)

Re: [patch, libfortran] [patch, fortran] Fix PR 79956, part two, attempt 2

[Markus Trippelsdorf]

On 2017.03.13 at 23:24 +0100, Thomas Koenig wrote:
> Hello world,
> 
> Following Richard's suggestion, I have implemented the GFC_ASSERT macro
> and used it to (hopefully) silence the ominous warning and allow
> further optimization.

Unfortunately the single GFC_ASSERT isn't enough:

libgfortran/intrinsics/reshape_generic.c: In function ‘reshape_internal’:
libgfortran/intrinsics/reshape_generic.c:257:21: warning: ‘sstride[0]’ may be used uninitialized in this function [-Wmaybe-uninitialized]
   sstride0 = sstride[0] * size;
              ~~~~~~~^~~
The following patch is needed to silence them all.

diff --git a/libgfortran/intrinsics/reshape_generic.c b/libgfortran/intrinsics/reshape_generic.c
index 43a822f87ae..d7c9e74853a 100644
--- a/libgfortran/intrinsics/reshape_generic.c
+++ b/libgfortran/intrinsics/reshape_generic.c
@@ -66,6 +66,7 @@ reshape_internal (parray *ret, parray *source, shape_type *shape,
   index_type shape_data[GFC_MAX_DIMENSIONS];
 
   rdim = GFC_DESCRIPTOR_EXTENT(shape,0);
+  GFC_ASSERT(rdim>0);
   if (rdim != GFC_DESCRIPTOR_RANK(ret))
     runtime_error("rank of return array incorrect in RESHAPE intrinsic");
 
@@ -158,6 +159,10 @@ reshape_internal (parray *ret, parray *source, shape_type *shape,
 
       source_extent = 1;
       sdim = GFC_DESCRIPTOR_RANK (source);
+      /* sdim is always > 0; this lets the compiler optimize more and
+         avoids a warning.  */
+      GFC_ASSERT(sdim>0);
+
       for (n = 0; n < sdim; n++)
 	{
 	  index_type se;
@@ -219,6 +224,7 @@ reshape_internal (parray *ret, parray *source, shape_type *shape,
     }
 
   sdim = GFC_DESCRIPTOR_RANK (source);
+  GFC_ASSERT(sdim>0);
   ssize = 1;
   sempty = 0;
   for (n = 0; n < sdim; n++)

-- 
Markus