[committed] Allow the target to set MAX_BITSIZE_MODE_ANY_MODE

[Richard Sandiford]

The default value of MAX_BITSIZE_MODE_ANY_MODE is calculated
from the initial mode sizes specified in the modes.def file.
The target needs to be able to override it if ADJUST_BYTESIZE
& co. can choose a bigger size.

Tested on aarch64-linux-gnu, x86_64-linux-gnu and powerpc64le-linux-gnu.
Also tested by comparing the before and after assembly output for at
least one target per CPU directory.  Applied (as a gen* patch).

Richard


2018-01-03  Richard Sandiford  <richard.sandif...@linaro.org>

gcc/
        * doc/rtl.texi (MAX_BITSIZE_MODE_ANY_MODE): Describe how the default
        is calculated and how it can be overridden.
        * genmodes.c (max_bitsize_mode_any_mode): New variable.
        (create_modes): Initialize it from MAX_BITSIZE_MODE_ANY_MODE,
        if defined.
        (emit_max_int): Use it to set the output MAX_BITSIZE_MODE_ANY_MODE,
        if nonzero.

Index: gcc/doc/rtl.texi
===================================================================
--- gcc/doc/rtl.texi    2018-01-03 09:44:10.691921247 +0000
+++ gcc/doc/rtl.texi    2018-01-03 09:44:10.854914708 +0000
@@ -1509,7 +1509,12 @@ compute integer values.
 
 @findex MAX_BITSIZE_MODE_ANY_MODE
 @item MAX_BITSIZE_MODE_ANY_MODE
-The bitsize of the largest mode on the target.   
+The bitsize of the largest mode on the target.  The default value is
+the largest mode size given in the mode definition file, which is
+always correct for targets whose modes have a fixed size.  Targets
+that might increase the size of a mode beyond this default should define
+@code{MAX_BITSIZE_MODE_ANY_MODE} to the actual upper limit in
+@file{@var{machine}-modes.def}.
 @end table
 
 @findex byte_mode
Index: gcc/genmodes.c
===================================================================
--- gcc/genmodes.c      2018-01-03 09:44:10.691921247 +0000
+++ gcc/genmodes.c      2018-01-03 09:44:10.854914708 +0000
@@ -792,6 +792,7 @@ #define ADJUST_FBIT(M, X)  _ADD_ADJUST (
 
 static int bits_per_unit;
 static int max_bitsize_mode_any_int;
+static int max_bitsize_mode_any_mode;
 
 static void
 create_modes (void)
@@ -811,6 +812,12 @@ create_modes (void)
 #else
   max_bitsize_mode_any_int = 0;
 #endif
+
+#ifdef MAX_BITSIZE_MODE_ANY_MODE
+  max_bitsize_mode_any_mode = MAX_BITSIZE_MODE_ANY_MODE;
+#else
+  max_bitsize_mode_any_mode = 0;
+#endif
 }
 
 #ifndef NUM_POLY_INT_COEFFS
@@ -989,12 +996,18 @@ emit_max_int (void)
   else
     printf ("#define MAX_BITSIZE_MODE_ANY_INT %d\n", max_bitsize_mode_any_int);
 
-  mmax = 0;
-  for (j = 0; j < MAX_MODE_CLASS; j++)
-    for (i = modes[j]; i; i = i->next)
-      if (mmax < i->bytesize)
-       mmax = i->bytesize;
-  printf ("#define MAX_BITSIZE_MODE_ANY_MODE (%d*BITS_PER_UNIT)\n", mmax);
+  if (max_bitsize_mode_any_mode == 0)
+    {
+      mmax = 0;
+      for (j = 0; j < MAX_MODE_CLASS; j++)
+       for (i = modes[j]; i; i = i->next)
+         if (mmax < i->bytesize)
+           mmax = i->bytesize;
+      printf ("#define MAX_BITSIZE_MODE_ANY_MODE (%d*BITS_PER_UNIT)\n", mmax);
+    }
+  else
+    printf ("#define MAX_BITSIZE_MODE_ANY_MODE %d\n",
+           max_bitsize_mode_any_mode);
 }
 
 /* Emit mode_size_inline routine into insn-modes.h header.  */