document EMIT_MIR_FOR_EACH_PANIC_STRATEGY

src/tests/compiletest.md

diff --git a/src/tests/compiletest.md b/src/tests/compiletest.md
index 4573a04..e3d044d 100644
--- a/src/tests/compiletest.md
+++ b/src/tests/compiletest.md
@@ -460,6 +460,10 @@
 In that case you can add `// EMIT_MIR_FOR_EACH_BIT_WIDTH` to
 your test, causing separate files to be generated for 32bit and 64bit systems.
 
+Similarly,
+to generate separate files for each panic strategy ("panic-abort" and "panic-unwind"),
+add `// EMIT_MIR_FOR_EACH_PANIC_STRATEGY` to the test.
+
 [`tests/mir-opt`]: https://github.com/rust-lang/rust/tree/HEAD/tests/mir-opt