2 files changed, 5 insertions, 21 deletions
diff --git a/src/doc/rustc-dev-guide/src/tests/compiletest.md b/src/doc/rustc-dev-guide/src/tests/compiletest.md
index 9f0c56dc4..5fc6ba809 100644
--- a/src/doc/rustc-dev-guide/src/tests/compiletest.md
+++ b/src/doc/rustc-dev-guide/src/tests/compiletest.md
@@ -24,6 +24,11 @@ See the [Adding new tests](adding.md) chapter for a tutorial on creating a new
 test, and the [Running tests](running.md) chapter on how to run the test
 suite.
 
+Compiletest itself tries to avoid running tests when the artifacts
+that are involved (mainly the compiler) haven't changed. You can use
+`x test --test-args --force-rerun` to rerun a test even when none of the
+inputs have changed.
+
 ## Test suites
 
 All of the tests are in the [`tests`] directory.
diff --git a/src/doc/rustc-dev-guide/src/tests/running.md b/src/doc/rustc-dev-guide/src/tests/running.md
index 96c869109..0a3de6f8b 100644
--- a/src/doc/rustc-dev-guide/src/tests/running.md
+++ b/src/doc/rustc-dev-guide/src/tests/running.md
@@ -175,27 +175,6 @@ By passing `--pass $mode`, you can reduce the testing time. For each
 mode, please see [Controlling pass/fail
 expectations](ui.md#controlling-passfail-expectations).
 
-## Using incremental compilation
-
-You can further enable the `--incremental` flag to save additional
-time in subsequent rebuilds:
-
-```bash
-./x.py test tests/ui --incremental --test-args issue-1234
-```
-
-If you don't want to include the flag with every command, you can
-enable it in the `config.toml`:
-
-```toml
-[rust]
-incremental = true
-```
-
-Note that incremental compilation will use more disk space than usual.
-If disk space is a concern for you, you might want to check the size
-of the `build` directory from time to time.
-
 ## Running tests with different "compare modes"
 
 UI tests may have different output depending on certain "modes" that