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[PATCH] Fix failing assertion in calls.c:store_unaligned_arguments_into_pseudos


Hello,

when implementing the new ABI for powerpc64le-linux, I ran into an assertion
failure in store_unaligned_arguments_into_pseudos:
            gcc_assert (args[i].partial % UNITS_PER_WORD == 0);

This can happen in the new ABI since we pass "homogeneous structures"
consisting of soleley floating point elements of the same type in
floating-point registers until they run out, and the rest of the
structure in memory.  If the structure member type is a 4-byte float,
and we only have an odd number of floating point registers available,
then args[i].partial can legitimately end up not being a multiple
of UNITS_PER_WORD (i.e. 8 on the platform).

Now, there are a number of similar checks that args[i].partial is
aligned elsewhere in calls.c and functions.c.  But for all of those
the logic is: if args[i].reg is a REG, then args[i].partial must be
a multiple of the word size; but if args[i].regs is a PARALLEL, then
args[i].partial can be any arbitrary value.  In the powerpc64le-linux
use case, the back-end always generates PARALLEL in this situation,
so it seemed the middle-end ought to support this -- and it does,
except for this one case.

However, looking more closely, it seems store_unaligned_arguments_into_pseudos
is not really useful for PARALLEL arguments in the first place.  What this
routine does is load arguments into args[i].aligned_regs.  But if we have
an argument where args[i].reg is a PARALLEL, args[i].aligned_regs will in
fact never be used later on at all!   Instead, PARALLEL will always be
handled directly via emit_group_move (in load_register_parameters), so
the code generated by store_unaligned_arguments_into_pseudos for such cases
is simply dead anyway.

Thus, I'd suggest to simply have store_unaligned_arguments_into_pseudos
skip PARALLEL arguments.

Tested on powerpc64-linux and powerpc64le-linux.

OK for mainline?

Bye,
Ulrich



ChangeLog:

2013-11-11  Ulrich Weigand  <Ulrich.Weigand@de.ibm.com>

	* calls.c (store_unaligned_arguments_into_pseudos): Skip PARALLEL
	arguments.

Index: gcc/gcc/calls.c
===================================================================
--- gcc.orig/gcc/calls.c
+++ gcc/gcc/calls.c
@@ -981,6 +981,7 @@ store_unaligned_arguments_into_pseudos (
 
   for (i = 0; i < num_actuals; i++)
     if (args[i].reg != 0 && ! args[i].pass_on_stack
+	&& GET_CODE (args[i].reg) != PARALLEL
 	&& args[i].mode == BLKmode
 	&& MEM_P (args[i].value)
 	&& (MEM_ALIGN (args[i].value)
-- 
  Dr. Ulrich Weigand
  GNU/Linux compilers and toolchain
  Ulrich.Weigand@de.ibm.com


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