From 39b646349f173a05222c3cf9b35262e453cb400c Mon Sep 17 00:00:00 2001
From: Geza Lore <glore@tenstorrent.com>
Date: Mon, 6 Jul 2026 18:02:37 +0100
Subject: [PATCH] Add --enable-light-debug configure option (#7886)

Change default debug build to use -O0 instead of -Og as the latter is
still not great debugging experience. Use -Og -gz, plus the new -ggdb1,
which together significantly cut down debug info size, to save CI cache
space, while still enabling -gdbbt tests to work.
---
 ci/ci-build.bash |  2 +-
 configure.ac     | 37 ++++++++++++++++++++++++++++++++-----
 2 files changed, 33 insertions(+), 6 deletions(-)

diff --git a/ci/ci-build.bash b/ci/ci-build.bash
index e9c2b2a20..64f037b33 100755
--- a/ci/ci-build.bash
+++ b/ci/ci-build.bash
@@ -60,7 +60,7 @@ esac
 ################################################################################
 # Configure
 
-CONFIGURE_ARGS="--prefix=$OPT_PREFIX --enable-longtests"
+CONFIGURE_ARGS="--prefix=$OPT_PREFIX --enable-longtests --enable-light-debug"
 if [ "$OPT_CCWARN" = 1 ]; then
   CONFIGURE_ARGS="$CONFIGURE_ARGS --enable-ccwarn"
 fi
diff --git a/configure.ac b/configure.ac
index 6376593ad..893bf91d0 100644
--- a/configure.ac
+++ b/configure.ac
@@ -129,6 +129,21 @@ AC_ARG_ENABLE([dev-gcov],
 AC_SUBST(CFG_WITH_DEV_GCOV)
 AC_MSG_RESULT($CFG_WITH_DEV_GCOV)
 
+# Flag to reduce the debug info in the debug executable to minimize its size
+AC_MSG_CHECKING(whether to reduce debug info in the debug executable)
+AC_ARG_ENABLE([light-debug],
+              [AS_HELP_STRING([--enable-light-debug],
+                              [Reduce the amount of debug information in the debug
+                               Verilator executable to minimize its size. Enable
+                               slight optimization. Enough for backtraces only.])],
+              [case "${enableval}" in
+                yes) CFG_WITH_LIGHT_DEBUG=yes ;;
+                no)  CFG_WITH_LIGHT_DEBUG=no ;;
+                *)   AC_MSG_ERROR([bad value '${enableval}' for --enable-light-debug]) ;;
+               esac],
+               CFG_WITH_LIGHT_DEBUG=no)
+AC_MSG_RESULT($CFG_WITH_LIGHT_DEBUG)
+
 # Special Substitutions - CFG_WITH_DEFENV
 AC_MSG_CHECKING(whether to use hardcoded paths)
 AC_ARG_ENABLE([defenv],
@@ -518,15 +533,27 @@ _MY_CXX_CHECK_OPT(CFG_CXXFLAGS_PARSER,-Wno-unused)
 AC_SUBST(CFG_CXXFLAGS_PARSER)
 
 # Flags for compiling the debug version of Verilator (in addition to above CFG_CXXFLAGS_SRC)
-if test "$CFG_WITH_DEV_GCOV" = "no"; then # Do not optimize for the coverage build
-_MY_CXX_CHECK_OPT(CFG_CXXFLAGS_DBG,-Og)
+if test "$CFG_WITH_LIGHT_DEBUG" = "yes"; then
+  # Slight optimization and minimal compressed debug info. This is enough for
+  # --gdb/--gdbbt backtraces, but omits the bulk of the debug info, which
+  # significantly reduces object file sizes. For CI or release builds.
+  if test "$CFG_WITH_DEV_GCOV" = "no"; then # Do not optimize for the coverage build
+    _MY_CXX_CHECK_OPT(CFG_CXXFLAGS_DBG,-Og)
+  fi
+  _MY_CXX_CHECK_OPT(CFG_CXXFLAGS_DBG,-ggdb1)
+  _MY_CXX_CHECK_OPT(CFG_CXXFLAGS_DBG,-fdebug-info-for-profiling) # For fully-qualified names with clang
+  _MY_CXX_CHECK_OPT(CFG_CXXFLAGS_DBG,-gz)
+else
+  # Full debug: no optimization, full debug info, for development.
+  _MY_CXX_CHECK_OPT(CFG_CXXFLAGS_DBG,-O0)
+  _MY_CXX_CHECK_OPT(CFG_CXXFLAGS_DBG,-ggdb)
 fi
-_MY_CXX_CHECK_OPT(CFG_CXXFLAGS_DBG,-ggdb)
-_MY_CXX_CHECK_OPT(CFG_CXXFLAGS_DBG,-gz)
 AC_SUBST(CFG_CXXFLAGS_DBG)
 
 # Flags for linking the debug version of Verilator (in addition to above CFG_LDFLAGS_SRC)
-_MY_LDLIBS_CHECK_OPT(CFG_LDFLAGS_DBG,-gz)
+if test "$CFG_WITH_LIGHT_DEBUG" = "yes"; then
+  _MY_LDLIBS_CHECK_OPT(CFG_LDFLAGS_DBG,-gz)
+fi
 AC_SUBST(CFG_LDFLAGS_DBG)
 
 # Flags for compiling the optimized version of Verilator (in addition to above CFG_CXXFLAGS_SRC)