[pr82089] Don't sign-extend SFV 1 in BImode

This is an update of the patch posted to PR82089 long ago.  We ran into the
same bug on GCN, so we need this fixed as part of this series.

2018-09-27  Andrew Stubbs  <ams@codesourcery.com>
            Tom de Vries  <tom@codesourcery.com>

	PR 82089

	gcc/
	* expmed.c (emit_cstore): Fix handling of result_mode == BImode and
	STORE_FLAG_VALUE == 1.

Co-Authored-By: Tom de Vries <tom@codesourcery.com>

From-SVN: r264666

gcc/ChangeLog

+2018-09-27  Andrew Stubbs  <ams@codesourcery.com>
+            Tom de Vries  <tom@codesourcery.com>
+
+	PR 82089
+
+	* expmed.c (emit_cstore): Fix handling of result_mode == BImode and
+	STORE_FLAG_VALUE == 1.
+
 2018-09-27  Andreas Krebbel  <krebbel@linux.ibm.com>
 
 	* config/s390/s390.md (PPA_TX_ABORT, PPA_OOO_BARRIER): New

gcc/expmed.c

@@ -5464,11 +5464,14 @@ emit_cstore (rtx target, enum insn_code icode, enum rtx_code code,
      If STORE_FLAG_VALUE does not have the sign bit set when
      interpreted in MODE, we can do this conversion as unsigned, which
      is usually more efficient.  */
-  if (GET_MODE_SIZE (int_target_mode) > GET_MODE_SIZE (result_mode))
+  if (GET_MODE_PRECISION (int_target_mode) > GET_MODE_PRECISION (result_mode))
     {
-      convert_move (target, subtarget,
-		    val_signbit_known_clear_p (result_mode,
-					       STORE_FLAG_VALUE));
+      gcc_assert (GET_MODE_PRECISION (result_mode) != 1
+		  || STORE_FLAG_VALUE == 1 || STORE_FLAG_VALUE == -1);
+
+      bool unsignedp = (STORE_FLAG_VALUE >= 0);
+      convert_move (target, subtarget, unsignedp);
+
       op0 = target;
       result_mode = int_target_mode;
     }