[LLVM CodeGen] Partially disable unsafe fp math (#2422)

src/codegen/llvm/llvm_common.cc

@@ -104,8 +104,8 @@ void ParseLLVMTargetOptions(const std::string& target_str,
   opt.LessPreciseFPMADOption = true;
   #endif
   opt.AllowFPOpFusion = llvm::FPOpFusion::Fast;
-  opt.UnsafeFPMath = true;
-  opt.NoInfsFPMath = true;
+  opt.UnsafeFPMath = false;
+  opt.NoInfsFPMath = false;
   opt.NoNaNsFPMath = true;
   if (soft_float_abi) {
     opt.FloatABIType = llvm::FloatABI::Soft;

tests/python/unittest/test_codegen_llvm.py

@@ -422,6 +422,39 @@ def test_llvm_div():
                 check_llvm(123, 133, d, 'uint8')
                 check_llvm(0, 256, d, 'uint8')
 
+def test_llvm_fp_math():
+    def check_llvm_reciprocal(n):
+        A = tvm.placeholder((n,), name='A')
+        B = tvm.compute((n,), lambda i: 1.0/(1e+37*A[i]), name='B')
+
+        s = tvm.create_schedule(B.op)
+        f = tvm.build(s, [A, B], "llvm")
+
+        a = tvm.nd.array(np.full((n,), 100, 'float32'))
+        b = tvm.nd.empty((n,), 'float32')
+        f(a, b)
+        tvm.testing.assert_allclose(b.asnumpy(), np.zeros((n,), 'float32'))
+
+    check_llvm_reciprocal(4)
+    check_llvm_reciprocal(8)
+    check_llvm_reciprocal(16)
+
+    def check_llvm_sigmoid(n):
+        A = tvm.placeholder((n,), name='A')
+        B = tvm.compute((n,), lambda i: tvm.sigmoid(A[i]), name='B')
+
+        s = tvm.create_schedule(B.op)
+        f = tvm.build(s, [A, B], "llvm")
+
+        a = tvm.nd.array(np.full((n,), -1000, 'float32'))
+        b = tvm.nd.empty((n,), 'float32')
+        f(a, b)
+        tvm.testing.assert_allclose(b.asnumpy(), np.zeros((n,), 'float32'))
+
+    check_llvm_sigmoid(4)
+    check_llvm_sigmoid(8)
+    check_llvm_sigmoid(16)
+
 if __name__ == "__main__":
     test_llvm_import()
     test_alignment()
@@ -439,3 +472,4 @@ if __name__ == "__main__":
     test_llvm_temp_space()
     test_llvm_lookup_intrin()
     test_llvm_div()
+    test_llvm_fp_math()