SERVER-69611 Set the -ffp-contract=off compiler option by default

(cherry picked from commit d8901a2835d3f464d394631d85dc7aa9493fc095)

2 files changed, 56 insertions, 0 deletions

diff --git a/SConstruct b/SConstruct
index a0700af4f92..bd2fb097deb 100755
--- a/SConstruct
+++ b/SConstruct
@@ -2115,6 +2115,15 @@ for suboption in get_option('experimental-runtime-hardening'):
     elif suboption.startswith('+'):
         selected_experimental_runtime_hardenings.add(suboption[1:])
 
+# Disable floating-point contractions such as forming of fused multiply-add operations.
+if env.ToolchainIs('clang', 'gcc'):
+    env.Append(CCFLAGS=["-ffp-contract=off"])
+else:
+    # msvc defaults to /fp:precise. Visual Studio 2022 does not emit floating-point contractions
+    # with /fp:precise, but previous versions can. Disable contractions altogether by using
+    # /fp:strict.
+    env.Append(CCFLAGS=["/fp:strict"])
+
 if env.TargetOSIs('linux'):
     env.Append( LIBS=["m"] )
     if not env.TargetOSIs('android'):
diff --git a/jstests/noPassthrough/floating_point_exp_contraction_off.js b/jstests/noPassthrough/floating_point_exp_contraction_off.js
new file mode 100644
index 00000000000..601dcd20f0d
--- /dev/null
+++ b/jstests/noPassthrough/floating_point_exp_contraction_off.js
@@ -0,0 +1,47 @@
+/**
+ * Validates that the server doesn't use fused multiply-add instructions (-ffp-contract=off).
+ *
+ * @tags: [
+ * multiversion_incompatible,
+ * ]
+ */
+
+(function() {
+'use strict';
+
+const conn = MongoRunner.runMongod();
+
+const coll = conn.getDB('test').getCollection('c');
+
+assert.commandWorked(coll.createIndex({loc: "2dsphere"}));
+assert.commandWorked(coll.insertOne({
+    "loc": {
+        "type": "Polygon",
+        "coordinates": [[
+            [-85.0329458713531, 41.3677690255613],
+            [-85.0296092033386, 41.3677690255613],
+            [-85.0296092033386, 41.360594065847],
+            [-85.0329458713531, 41.360594065847],
+            [-85.0329458713531, 41.3677690255613]
+        ]]
+    }
+}));
+
+// Assert that the query returns the document. If the query does not return any result, then
+// this is likely because of different rounding due to fused multiply-add instructions on platforms
+// that have native support, like arm64.
+assert.eq(
+    1,
+    coll.find({
+            "loc": {
+                "$near": {
+                    "$geometry":
+                        {"type": "Point", "coordinates": [-85.031218528747559, 41.364586470348961]},
+                    "$maxDistance": 0
+                }
+            }
+        })
+        .itcount());
+
+MongoRunner.stopMongod(conn);
+}());