[BOLT][docs] Add note regarding DWARF v5 support to README.md

Reviewed By: Amir, yota9

Differential Revision: https://reviews.llvm.org/D118284

diff --git a/bolt/README.md b/bolt/README.md
index 22a583d..22bf2a6 100644 (file)
--- a/bolt/README.md
+++ b/bolt/README.md
@@ -30,6 +30,14 @@ compiler option. Since GCC8 enables this option by default, you have to
 explicitly disable it by adding `-fno-reorder-blocks-and-partition` flag if
 you are compiling with GCC8 or above.
 
+NOTE2: DWARF v5 is the new debugging format generated by the latest LLVM and GCC
+compilers. It offers several benefits over the previous DWARF v4. Currently, the
+support for v5 is a work in progress for BOLT. While you will be able to
+optimize binaries produced by the latest compilers, until the support is
+complete, you will not be able to update the debug info with
+`-update-debug-sections`. To temporarily work around the issue, we recommend
+compiling binaries with `-gdwarf-4` option that forces DWARF v4 output.
+
 PIE and .so support has been added recently. Please report bugs if you
 encounter any issues.