Fix PR 71627 - unable to find a register to spill

Tweak find_valid_class_1 to consider a reg class if atleast one regno in
that class is ok.

Previously, even if no regno was in_hard_reg_set_p, the code goes ahead and
considers rclass as valid. bad was set only if a regno was in the reg
class *and* HARD_REGNO_MODE_OK was false - if both were false, bad wasn't
set and the reload got a wrong rclass. If that happened to be the best
one, this eventually lead to find_reg running out of registers to
spill, because the chosen rclass wouldn't have enough regs.

Also, it expected every regno in rclass to be valid for mode
i.e., if any regno fails HARD_REGNO_MODE_OK, it rejected the rclass. The
comments in the original commit for find_valid_class_1 say atleast one
regno is ok. This was updated to say "class which contains only
registers" when in_hard_reg_set_p was introduced in place of just
TEST_HARD_REG_BIT.

This commit fixes both of the above problems by not breaking out of the loop
on first unavailable regno. Instead, it computes the rclass size consisting
of all regnos in that class valid for the current mode.

If that computed size is zero, the rclass would be skipped, as it won't
beat best_size. Otherwise, the computed size is used to choose the best
rclass, instead of the static size from reg_class_size.

gcc/

2016-10-21  Senthil Kumar Selvaraj  <senthil_kumar.selvaraj@atmel.com>

	PR target/71627
	* reload.c (find_valid_class_1): Allow regclass if atleast one
	regno in regclass is ok. Compute and use rclass size based on
	actually available regnos for mode in rclass.

gcc/testsuite/

2016-10-21  Senthil Kumar Selvaraj  <senthil_kumar.selvaraj@atmel.com>

	PR target/71627
	* gcc.target/avr/pr71627.c: New test

From-SVN: r241400

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 66f78be9b9955d0f655b7ee31b63f131e920ae01..8f7a1b0cb258fde588d6852e31932c4be3754415 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,10 @@
+2016-10-21  Senthil Kumar Selvaraj  <senthil_kumar.selvaraj@atmel.com>
+
+       PR target/71627
+       * reload.c (find_valid_class_1): Allow regclass if atleast one
+       regno in regclass is ok. Compute and use rclass size based on
+       actually available regnos for mode in rclass.
+
 2016-10-21  Eric Botcazou  <ebotcazou@adacore.com>
 
        * config/sparc/sparc-modes.def (CCV): New.

diff --git a/gcc/reload.c b/gcc/reload.c
index 9a859e5b45bfa09ffdf69b3e38ae7391d56d7ba4..651755298ab828764c540f5032bb466762bb9083 100644 (file)
--- a/gcc/reload.c
+++ b/gcc/reload.c
@@ -715,25 +715,23 @@ find_valid_class_1 (machine_mode outer ATTRIBUTE_UNUSED,
 
   for (rclass = 1; rclass < N_REG_CLASSES; rclass++)
     {
-      int bad = 0;
-      for (regno = 0; regno < FIRST_PSEUDO_REGISTER && !bad; regno++)
-       {
-         if (in_hard_reg_set_p (reg_class_contents[rclass], mode, regno)
-             && !HARD_REGNO_MODE_OK (regno, mode))
-           bad = 1;
-       }
-      
-      if (bad)
-       continue;
+      unsigned int computed_rclass_size = 0;
+
+      for (regno = 0; regno < FIRST_PSEUDO_REGISTER; regno++)
+        {
+          if (in_hard_reg_set_p (reg_class_contents[rclass], mode, regno)
+              && (HARD_REGNO_MODE_OK (regno, mode)))
+            computed_rclass_size++;
+        }
 
       cost = register_move_cost (outer, (enum reg_class) rclass, dest_class);
 
-      if ((reg_class_size[rclass] > best_size
+      if ((computed_rclass_size > best_size
           && (best_cost < 0 || best_cost >= cost))
          || best_cost > cost)
        {
          best_class = (enum reg_class) rclass;
-         best_size = reg_class_size[rclass];
+         best_size = computed_rclass_size;
          best_cost = register_move_cost (outer, (enum reg_class) rclass,
                                          dest_class);
        }

diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 0e32435bba42d1774583ed361a1a6494f71802bb..771daa35ba318a570aa5db62c3c181428d737e67 100644 (file)
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2016-10-21  Senthil Kumar Selvaraj  <senthil_kumar.selvaraj@atmel.com>
+
+       PR target/71627
+       * gcc.target/avr/pr71627.c: New test
+
 2016-10-21  Eric Botcazou  <ebotcazou@adacore.com>
 
        * gcc.target/sparc/overflow-1.c: New test.

diff --git a/gcc/testsuite/gcc.target/avr/pr71627.c b/gcc/testsuite/gcc.target/avr/pr71627.c
new file mode 100644 (file)
index 0000000..eaef3d2
--- /dev/null
+++ b/gcc/testsuite/gcc.target/avr/pr71627.c
@@ -0,0 +1,14 @@
+/* { dg-do compile } */
+/* { dg-options "-O1" } */
+
+
+extern volatile __memx const long  a, b, c, d, e, f;
+extern volatile long result;
+
+extern void vfunc (const char*, ...);
+
+void foo (void)
+{
+       result = a + b + c + d + e + f;
+       vfunc ("text", a, b, c, d, e, f, result);
+}