[PATCH] Fix and testcases for pr72747

Will Schmidt will_schmidt@vnet.ibm.com
Thu Oct 27 15:37:00 GMT 2016


Hi,

Per PR72747, A statement such as "v = vec_splats (1);" correctly
initializes a vector.  However, a statement such as "v[1] = v[0] =
vec_splats (1);" initializes both v[1] and v[0] to random garbage.

It has been determined that this is occurring because we did not emit
the actual initialization statement before our final exit from
gimplify_init_constructor, at which time we lose the expression when we
assign *expr_p to either NULL or object.  This problem affected both constant
and non-constant initializers.  Corrected this by moving the logic to
emit the statement up earlier within the if/else logic.

Bootstrapped and make check ran without regressions on
powerpc64le-unknown-linux-gnu.

OK for trunk?

Thanks,
-Will

gcc:
2016-10-26  Will Schmidt <will_schmidt@vnet.ibm.com>

        PR middle-end/72747
        * gimplify.c (gimplify_init_constructor): Move emit of constructor
        assignment to earlier in the if/else logic.

testsuite:
2016-10-26  Will Schmidt <will_schmidt@vnet.ibm.com>

        PR middle-end/72747
        * c-c++-common/pr72747-1.c: New test.
        * c-c++-common/pr72747-2.c: Likewise.

Index: gcc/gimplify.c
===================================================================
--- gcc/gimplify.c	(revision 241600)
+++ gcc/gimplify.c	(working copy)
@@ -4730,24 +4730,23 @@
 
   if (ret == GS_ERROR)
     return GS_ERROR;
-  else if (want_value)
+  /* If we have gimplified both sides of the initializer but have
+     not emitted an assignment, do so now.  */
+  if (*expr_p)
     {
+      tree lhs = TREE_OPERAND (*expr_p, 0);
+      tree rhs = TREE_OPERAND (*expr_p, 1);
+      gassign *init = gimple_build_assign (lhs, rhs);
+      gimplify_seq_add_stmt (pre_p, init);
+    }
+  if (want_value)
+    {
       *expr_p = object;
       return GS_OK;
     }
   else
     {
-      /* If we have gimplified both sides of the initializer but have
-	 not emitted an assignment, do so now.  */
-      if (*expr_p)
-	{
-	  tree lhs = TREE_OPERAND (*expr_p, 0);
-	  tree rhs = TREE_OPERAND (*expr_p, 1);
-	  gassign *init = gimple_build_assign (lhs, rhs);
-	  gimplify_seq_add_stmt (pre_p, init);
-	  *expr_p = NULL;
-	}
-
+      *expr_p = NULL;
       return GS_ALL_DONE;
     }
 }
Index: gcc/testsuite/c-c++-common/pr72747-1.c
===================================================================
--- gcc/testsuite/c-c++-common/pr72747-1.c	(revision 0)
+++ gcc/testsuite/c-c++-common/pr72747-1.c	(working copy)
@@ -0,0 +1,16 @@
+/* { dg-do compile } */
+/* { dg-require-effective-target powerpc_altivec_ok } */
+/* { dg-options "-maltivec -fdump-tree-gimple" } */
+
+/* PR 72747: Test that cascaded definition is happening for constant vectors. */
+
+#include <altivec.h>
+
+int main (int argc, char *argv[])
+{
+	__vector int v1,v2;
+	v1 = v2 = vec_splats ((int) 42);
+	return 0;
+}
+/* { dg-final { scan-tree-dump-times " v2 = { 42, 42, 42, 42 }" 1 "gimple" } } */
+
Index: gcc/testsuite/c-c++-common/pr72747-2.c
===================================================================
--- gcc/testsuite/c-c++-common/pr72747-2.c	(revision 0)
+++ gcc/testsuite/c-c++-common/pr72747-2.c	(working copy)
@@ -0,0 +1,18 @@
+/* { dg-do compile } */
+/* { dg-require-effective-target powerpc_altivec_ok } */
+/* { dg-options "-c -maltivec -fdump-tree-gimple" } */
+
+/* PR 72747: test that cascaded definition is happening for non constants. */
+
+void foo ()
+{
+  extern int i;
+  __vector int v,w;
+    v = w = (vector int) { i };
+}
+
+int main (int argc, char *argv[])
+{
+  return 0;
+}
+/* { dg-final { scan-tree-dump-times " w = {i.0_1}" 1 "gimple" } } */




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