From 0769caf8bbf0bc6ea3c681e5af7d79291fae2e2f Mon Sep 17 00:00:00 2001
From: Julian Büning <julian.buening@comsys.rwth-aachen.de>
Date: Fri, 18 Sep 2020 18:14:56 +0200
Subject: implement fneg instruction

---
 lib/Core/Executor.cpp | 14 ++++++++++++++
 test/Feature/FNeg.ll  | 19 +++++++++++++++++++
 2 files changed, 33 insertions(+)
 create mode 100644 test/Feature/FNeg.ll

diff --git a/lib/Core/Executor.cpp b/lib/Core/Executor.cpp
index 7fac4fa4..de35710f 100644
--- a/lib/Core/Executor.cpp
+++ b/lib/Core/Executor.cpp
@@ -2465,6 +2465,20 @@ void Executor::executeInstruction(ExecutionState &state, KInstruction *ki) {
 
     // Floating point instructions
 
+#if LLVM_VERSION_CODE >= LLVM_VERSION(8, 0)
+  case Instruction::FNeg: {
+    ref<ConstantExpr> arg =
+        toConstant(state, eval(ki, 0, state).value, "floating point");
+    if (!fpWidthToSemantics(arg->getWidth()))
+      return terminateStateOnExecError(state, "Unsupported FNeg operation");
+
+    llvm::APFloat Res(*fpWidthToSemantics(arg->getWidth()), arg->getAPValue());
+    Res = llvm::neg(Res);
+    bindLocal(ki, state, ConstantExpr::alloc(Res.bitcastToAPInt()));
+    break;
+  }
+#endif
+
   case Instruction::FAdd: {
     ref<ConstantExpr> left = toConstant(state, eval(ki, 0, state).value,
                                         "floating point");
diff --git a/test/Feature/FNeg.ll b/test/Feature/FNeg.ll
new file mode 100644
index 00000000..cdea6aaa
--- /dev/null
+++ b/test/Feature/FNeg.ll
@@ -0,0 +1,19 @@
+; REQUIRES: geq-llvm-8.0
+; RUN: %llvmas %s -o %t.bc
+; RUN: rm -rf %t.klee-out
+; RUN: %klee -exit-on-error -output-dir=%t.klee-out -optimize=false %t.bc
+
+define i32 @main() {
+  %1 = fneg double 2.000000e-01
+  %2 = fcmp oeq double %1, -2.000000e-01
+  br i1 %2, label %success, label %fail
+
+success:
+  ret i32 0
+
+fail:
+  call void @abort()
+  unreachable
+}
+
+declare void @abort() noreturn nounwind
-- 
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