[PATCH] Fix store-merging vuse handling (PR tree-optimization/83170, PR tree-optimization/83241)

[Jakub Jelinek <jakub@redhat.com>]

Hi!

The bswap infrastructure uses the vuse field to make sure all the loads are
having the same gimple_vuse and also uses it in bswap_replace.
When this infrastructure is used inside of the store-merging pass, the
problem is that the old stores are being removed and new added, so
gimple_vuse of the loads we record during process_stmt can change.
So, this patch updates the vuse fields before we plan to use it (in
try_coalesce_bswap for the checking and in output_merged_stores for the
bswap_replace purposes).

Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

2017-12-01  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/83170
	PR tree-optimization/83241
	* gimple-ssa-store-merging.c
	(imm_store_chain_info::try_coalesce_bswap): Update vuse field from
	gimple_vuse (ins_stmt) in case it has changed.
	(imm_store_chain_info::output_merged_store): Likewise.

	* gcc.dg/store_merging_17.c: New test.

--- gcc/gimple-ssa-store-merging.c.jj	2017-12-01 09:17:36.000000000 +0100
+++ gcc/gimple-ssa-store-merging.c	2017-12-01 16:03:40.806918965 +0100
@@ -2384,6 +2384,9 @@ imm_store_chain_info::try_coalesce_bswap
       this_n.type = type;
       if (!this_n.base_addr)
 	this_n.range = try_size / BITS_PER_UNIT;
+      else
+	/* Update vuse in case it has changed by output_merged_stores.  */
+	this_n.vuse = gimple_vuse (info->ins_stmt);
       unsigned int bitpos = info->bitpos - infof->bitpos;
       if (!do_shift_rotate (LSHIFT_EXPR, &this_n,
 			    BYTES_BIG_ENDIAN
@@ -3341,10 +3344,16 @@ imm_store_chain_info::output_merged_stor
 	 we've checked the aliasing already in try_coalesce_bswap and
 	 we want to sink the need load into seq.  So need to use new_vuse
 	 on the load.  */
-      if (n->base_addr && n->vuse == NULL)
+      if (n->base_addr)
 	{
-	  n->vuse = new_vuse;
-	  ins_stmt = NULL;
+	  if (n->vuse == NULL)
+	    {
+	      n->vuse = new_vuse;
+	      ins_stmt = NULL;
+	    }
+	  else
+	    /* Update vuse in case it has changed by output_merged_stores.  */
+	    n->vuse = gimple_vuse (ins_stmt);
 	}
       bswap_res = bswap_replace (gsi_start (seq), ins_stmt, fndecl,
 				 bswap_type, load_type, n, bswap);
--- gcc/testsuite/gcc.dg/store_merging_17.c.jj	2017-12-01 16:07:20.590224536 +0100
+++ gcc/testsuite/gcc.dg/store_merging_17.c	2017-12-01 16:07:01.000000000 +0100
@@ -0,0 +1,17 @@
+/* PR tree-optimization/83241 */
+/* { dg-do compile { target store_merge } } */
+/* { dg-options "-O2" } */
+
+struct S { int a; short b[32]; } e;
+struct T { volatile int c; int d; } f;
+
+void
+foo ()
+{
+  struct T g = f;
+  e.b[0] = 6;
+  e.b[1] = 6;
+  e.b[4] = g.d;
+  e.b[5] = g.d >> 16;
+  e.a = 1;
+}

	Jakub