Handle FPSW register in exegesis annotator

This was causing errors on one of the BHive bbs. We simply skip doing
anything with the register since we can not really set the status of the
floating point environment.

Reviewers: ondrasej, virajbshah, orodley

Reviewed By: orodley

Pull Request: #340

Author: boomanaiden154

gematria/datasets/find_accessed_addrs_exegesis.cc

@@ -160,6 +160,11 @@ Expected<ExecutionAnnotations> ExegesisAnnotator::findAccessedAddrs(
       continue;
     }
 
+    // We cannot explicitly set FPSW, so skip it if it comes up.
+    if (RegisterIndex == X86::FPSW) {
+      continue;
+    }
+
     RegisterAndValue *NewRegisterValue = MemAnnotations.add_initial_registers();
     NewRegisterValue->set_register_name(
         State.getRegInfo().getName(RegisterIndex));

gematria/datasets/find_accessed_addrs_exegesis_test.cc

@@ -298,5 +298,15 @@ TEST_F(FindAccessedAddrsExegesisTest, AVX512XMMYMMRegisters) {
                     "YMM16")}));
 }
 
+TEST_F(FindAccessedAddrsExegesisTest, FPSWRegister) {
+  auto AddrsOrErr = FindAccessedAddrsExegesis(R"asm(
+    fnstsw
+  )asm");
+  ASSERT_TRUE(static_cast<bool>(AddrsOrErr));
+  EXPECT_THAT(AddrsOrErr->initial_registers(),
+              Not(Contains(Property(
+                  "register_name", &RegisterAndValue::register_name, "FPSW"))));
+}
+
 }  // namespace
 }  // namespace gematria