Make assemble_real generate canonical CONST_INTs

assemble_real used GEN_INT to create integers directly from the
longs returned by real_to_target.  assemble_integer then went on
to interpret the const_ints as though they had the mode corresponding
to the accompanying size parameter:

      imode = mode_for_size (size * BITS_PER_UNIT, mclass, 0).require ();

      for (i = 0; i < size; i += subsize)
	{
	  rtx partial = simplify_subreg (omode, x, imode, i);

But in the assemble_real case, X might not be canonical for IMODE.

If the interface to assemble_integer is supposed to allow outputting
(say) the low 4 bytes of a DImode integer, then the simplify_subreg
above is wrong.  But if the number of bytes passed to assemble_integer
is supposed to be the number of bytes that the integer actually contains,
assemble_real is wrong.

This patch takes the latter interpretation and makes assemble_real
generate const_ints that are canonical for the number of bytes passed.

The flip_storage_order handling assumes that each long is a full
SImode, which e.g. excludes BITS_PER_UNIT != 8 and float formats
whose memory size is not a multiple of 32 bits (which includes
HFmode at least).  The patch therefore leaves that code alone.
If interpreting each integer as SImode is correct, the const_ints
that it generates are also correct.

2019-09-18  Richard Sandiford  <richard.sandiford@arm.com>

gcc/
	* varasm.c (assemble_real): Generate canonical const_ints.

From-SVN: r275873

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 1907307c7622460dbb760eb816e710fea71ca079..a6869cfcbdbb7bf75858c73c2ce398890ae5dcab 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,7 @@
+2019-09-18  Richard Sandiford  <richard.sandiford@arm.com>
+
+       * varasm.c (assemble_real): Generate canonical const_ints.
+
 2019-09-18  Richard Biener  <rguenther@suse.de>
 
        PR lto/91763

diff --git a/gcc/varasm.c b/gcc/varasm.c
index a7c22523f9faf12c96b917b37b34777ca750cb02..57365ad2e761a0f3e91f7b930eabb379054fc965 100644 (file)
--- a/gcc/varasm.c
+++ b/gcc/varasm.c
@@ -2873,25 +2873,27 @@ assemble_real (REAL_VALUE_TYPE d, scalar_float_mode mode, unsigned int align,
   real_to_target (data, &d, mode);
 
   /* Put out the first word with the specified alignment.  */
+  unsigned int chunk_nunits = MIN (nunits, units_per);
   if (reverse)
     elt = flip_storage_order (SImode, gen_int_mode (data[nelts - 1], SImode));
   else
-    elt = GEN_INT (data[0]);
-  assemble_integer (elt, MIN (nunits, units_per), align, 1);
-  nunits -= units_per;
+    elt = GEN_INT (sext_hwi (data[0], chunk_nunits * BITS_PER_UNIT));
+  assemble_integer (elt, chunk_nunits, align, 1);
+  nunits -= chunk_nunits;
 
   /* Subsequent words need only 32-bit alignment.  */
   align = min_align (align, 32);
 
   for (int i = 1; i < nelts; i++)
     {
+      chunk_nunits = MIN (nunits, units_per);
       if (reverse)
        elt = flip_storage_order (SImode,
                                  gen_int_mode (data[nelts - 1 - i], SImode));
       else
-       elt = GEN_INT (data[i]);
-      assemble_integer (elt, MIN (nunits, units_per), align, 1);
-      nunits -= units_per;
+       elt = GEN_INT (sext_hwi (data[i], chunk_nunits * BITS_PER_UNIT));
+      assemble_integer (elt, chunk_nunits, align, 1);
+      nunits -= chunk_nunits;
     }
 }
 \f