[Patch AArch64] Warn on unpredictable stlxrb , stlxrh and stlxr cases.

[Ramana Radhakrishnan]

A recent case in golang highlighted that gas wasn't warning on these
unpredictable cases in the architecture. Fixed thusly.

Tested aarch64-none-elf.

Ok ?


regards
Ramana

2018-06-17  Ramana Radhakrishnan  <ramana.radhakrishnan@arm.com>

     	* config/tc-aarch64.c (warn_unpredictable_ldst): Add unpredictable
     	cases for ldxp, stlxrb, stlxrh, stlxr.
     	* testsuite/gas/aarch64/diagnostic.s: New tests.
     	* testsuite/gas/aarch64/diagnostic.l: Adjust.
-------------- next part --------------
diff --git a/gas/config/tc-aarch64.c b/gas/config/tc-aarch64.c
index 660fa7c..e5d819a 100644
--- a/gas/config/tc-aarch64.c
+++ b/gas/config/tc-aarch64.c
@@ -6703,6 +6703,22 @@ warn_unpredictable_ldst (aarch64_instruction *instr, char *str)
 	  && opnds[0].reg.regno == opnds[1].reg.regno)
 	    as_warn (_("unpredictable load of register pair -- `%s'"), str);
       break;
+
+    case ldstexcl:
+      /* It is unpredictable if the destination and status registers are the
+	 same.  */
+      if ((aarch64_get_operand_class (opnds[0].type)
+	   == AARCH64_OPND_CLASS_INT_REG)
+	  && (aarch64_get_operand_class (opnds[1].type)
+	      == AARCH64_OPND_CLASS_INT_REG)
+	  && (opnds[0].reg.regno == opnds[1].reg.regno
+	      || opnds[0].reg.regno == opnds[2].reg.regno))
+	as_warn (_("unpredictable: identical transfer and status registers"
+		   " --`%s'"),
+		 str);
+
+      break;
+
     default:
       break;
     }
diff --git a/gas/testsuite/gas/aarch64/diagnostic.l b/gas/testsuite/gas/aarch64/diagnostic.l
index 00bb512..6aae306 100644
--- a/gas/testsuite/gas/aarch64/diagnostic.l
+++ b/gas/testsuite/gas/aarch64/diagnostic.l
@@ -172,3 +172,13 @@
 [^:]*:300: Warning: ignoring redefinition of register alias 'ip1'
 [^:]*:301: Warning: ignoring redefinition of register alias 'lr'
 [^:]*:302: Warning: ignoring redefinition of register alias 'fp'
+[^:]*:304: Warning: unpredictable: identical transfer and status registers --`stlxrb w26,w26,\[x0\]'
+[^:]*:305: Warning: unpredictable: identical transfer and status registers --`stlxrh w26,w26,\[x1\]'
+[^:]*:306: Warning: unpredictable: identical transfer and status registers --`stlxr w26,w26,\[x2\]'
+[^:]*:307: Warning: unpredictable: identical transfer and status registers --`stlxrb w26,w27,\[x26\]'
+[^:]*:308: Warning: unpredictable: identical transfer and status registers --`stlxrh w26,w27,\[x26\]'
+[^:]*:309: Warning: unpredictable: identical transfer and status registers --`stlxr w26,w27,\[x26\]'
+[^:]*:310: Warning: unpredictable: identical transfer and status registers --`stlxr w26,x27,\[x26\]'
+[^:]*:311: Warning: unpredictable: identical transfer and status registers --`stlxr w26,x26,\[x3\]'
+[^:]*:312: Warning: unpredictable: identical transfer and status registers --`ldxp x26,x26,\[x5\]'
+[^:]*:313: Warning: unpredictable: identical transfer and status registers --`ldxp x26,x1,\[x26\]'
diff --git a/gas/testsuite/gas/aarch64/diagnostic.s b/gas/testsuite/gas/aarch64/diagnostic.s
index a62327d..c18c48e 100644
--- a/gas/testsuite/gas/aarch64/diagnostic.s
+++ b/gas/testsuite/gas/aarch64/diagnostic.s
@@ -300,3 +300,14 @@
 	ip1	.req 	x1
 	lr	.req 	x2
 	fp	.req 	x3
+
+	stlxrb 	w26, w26, [x0]
+	stlxrh	w26, w26, [x1]
+	stlxr 	w26, w26, [x2]
+	stlxrb 	w26, w27, [x26]
+	stlxrh	w26, w27, [x26]
+	stlxr 	w26, w27, [x26]
+	stlxr 	w26, x27, [x26]
+	stlxr	w26, x26, [x3]
+	ldxp	x26, x26, [x5]
+	ldxp	x26, x1, [x26]