Force IFN_LOAD/STORE_LANES operands to be memory (PR91577)

[Richard Sandiford <richard dot sandiford at arm dot com>]

This patch uses the workaround Richi suggested in the PR: make
discover_nonconstant_array_refs mark the source of an IFN_LOAD_LANES
call and the destination of an IFN_STORE_LANES call as addressable,
so that they don't end up being REG rtxes during expansion.

I had to move the discover_nonconstant_array_refs call outside the
currently_expanding_to_rtl block since otherwise mark_addressable
just queues the decision for later.

Tested on aarch64-linux-gnu.  OK to install?

Richard


2019-09-04  Richard Sandiford  <richard.sandiford@arm.com>

gcc/
	PR middle-end/91577
	* cfgexpand.c (discover_nonconstant_array_refs): Force the source
	of an IFN_LOAD_LANES call and the destination of an IFN_STORE_LANES
	call to be in memory.
	(pass_expand::execute): Call discover_nonconstant_array_refs before
	setting currently_expanding_to_rtl.

gcc/testsuite/
	PR middle-end/91577
	* gfortran.dg/pr91577.f90: New test, taken from temporary_1.f90.

Index: gcc/cfgexpand.c
===================================================================
--- gcc/cfgexpand.c	2019-07-12 11:33:27.712037291 +0100
+++ gcc/cfgexpand.c	2019-09-04 10:16:17.798875071 +0100
@@ -6155,7 +6155,24 @@ discover_nonconstant_array_refs (void)
       {
 	gimple *stmt = gsi_stmt (gsi);
 	if (!is_gimple_debug (stmt))
-	  walk_gimple_op (stmt, discover_nonconstant_array_refs_r, NULL);
+	  {
+	    walk_gimple_op (stmt, discover_nonconstant_array_refs_r, NULL);
+	    gcall *call = dyn_cast <gcall *> (stmt);
+	    if (call && gimple_call_internal_p (call))
+	      switch (gimple_call_internal_fn (call))
+		{
+		case IFN_LOAD_LANES:
+		  /* The source must be a MEM.  */
+		  mark_addressable (gimple_call_arg (call, 0));
+		  break;
+		case IFN_STORE_LANES:
+		  /* The destination must be a MEM.  */
+		  mark_addressable (gimple_call_lhs (call));
+		  break;
+		default:
+		  break;
+		}
+	  }
       }
 }
 
@@ -6353,6 +6370,9 @@ pass_expand::execute (function *fun)
 	    avoid_deep_ter_for_debug (gsi_stmt (gsi), 0);
     }
 
+  /* Mark arrays indexed with non-constant indices with TREE_ADDRESSABLE.  */
+  discover_nonconstant_array_refs ();
+
   /* Make sure all values used by the optimization passes have sane
      defaults.  */
   reg_renumber = 0;
@@ -6387,9 +6407,6 @@ pass_expand::execute (function *fun)
      Also, final expects a note to appear there.  */
   emit_note (NOTE_INSN_DELETED);
 
-  /* Mark arrays indexed with non-constant indices with TREE_ADDRESSABLE.  */
-  discover_nonconstant_array_refs ();
-
   targetm.expand_to_rtl_hook ();
   crtl->init_stack_alignment ();
   fun->cfg->max_jumptable_ents = 0;
Index: gcc/testsuite/gfortran.dg/pr91577.f90
===================================================================
--- /dev/null	2019-07-30 08:53:31.317691683 +0100
+++ gcc/testsuite/gfortran.dg/pr91577.f90	2019-09-04 10:16:17.798875071 +0100
@@ -0,0 +1,28 @@
+! { dg-do run }
+! { dg-additional-options "--param max-completely-peel-loop-nest-depth=1" }
+! PR 27662. Don't zero the first stride to indicate a temporary. It
+! may be used later.
+program pr27662
+ implicit none
+ real(kind=kind(1.0d0)), dimension (2, 2):: x, y, z;
+ integer i, j
+ x(1,1) = 1.d0
+ x(2,1) = 0.d0
+ x(1,2) = 0.d0
+ x(2,2) = 1.d0
+ z = matmul (x, transpose (test ()))
+ do i = 1, size (x, 1)
+   do j = 1, size (x, 2)
+     if (x (i, j) .ne. z (i, j)) STOP 1
+   end do
+ end do
+
+contains
+ function test () result (res)
+   real(kind=kind(1.0d0)), dimension(2,2) :: res
+   res(1,1) = 1.d0
+   res(2,1) = 0.d0
+   res(1,2) = 0.d0
+   res(2,2) = 1.d0
+ end function
+end