From 42447f4b68235b545cc0e1b91111079c155dc2f8 Mon Sep 17 00:00:00 2001
From: Bruce Hill <bruce@bruce-hill.com>
Date: Sun, 19 Oct 2025 14:44:30 -0400
Subject: Add makefile config option for LTO

---
 Makefile     |  2 --
 configure.sh | 11 +++++++++++
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/Makefile b/Makefile
index 82bbebf9..5f0978ca 100644
--- a/Makefile
+++ b/Makefile
@@ -37,7 +37,6 @@ CCONFIG=-std=c2x -fPIC \
 		-fno-signed-zeros -fno-trapping-math \
 		-fvisibility=hidden -fdollars-in-identifiers \
 		-DGC_THREADS
-LTO=
 LDFLAGS=
 INCLUDE_DIRS=
 CWARN=-Wall -Wextra -Wno-format -Wno-format-security -Wshadow \
@@ -68,7 +67,6 @@ endif
 OWNER=$(shell ls -ld '$(PREFIX)' | awk '{print $$3}')
 
 ifeq ($(shell $(CC) -v 2>&1 | grep -c "gcc version"), 1)
-	LTO += -flto=auto -fno-fat-lto-objects -Wl,-flto
 	CWARN += -Werror -Wsign-conversion -Walloc-zero -Wduplicated-branches -Wduplicated-cond -Wjump-misses-init \
 			 -Wlogical-op -Wpacked-not-aligned -Wshadow=compatible-local -Wshadow=global -Wshadow=local \
 			 -Wsuggest-attribute=const -Wsuggest-attribute=noreturn -Wsuggest-attribute=pure \
diff --git a/configure.sh b/configure.sh
index 1b5bd272..a4a8daa5 100755
--- a/configure.sh
+++ b/configure.sh
@@ -37,8 +37,19 @@ read DEFAULT_C_COMPILER
 if [ -z "$DEFAULT_C_COMPILER" ]; then DEFAULT_C_COMPILER="cc"; fi
 DEFAULT_C_COMPILER="${DEFAULT_C_COMPILER/#\~/$HOME}"
 
+printf '\033[1mDo you want to build the compiler with Link Time Optimization (LTO)?\033[m\n\033[2m(This makes building the Tomo compiler slower, but makes running Tomo programs faster)\033[m\n\033[1m[y/N]\033[m '
+read USE_LTO
+if [ "$USE_LTO" = "y" -o "$USE_LTO" = "Y" ]; then
+    if $DEFAULT_C_COMPILER -v 2>&1 | grep -q "gcc version"; then
+        LTO="-flto=auto -fno-fat-lto-objects -Wl,-flto";
+    elif $DEFAULT_C_COMPILER -v 2>&1 | grep -q "clang version"; then
+        LTO="-flto=thin";
+    fi
+fi
+
 cat <<END >config.mk
 PREFIX=$PREFIX
 DEFAULT_C_COMPILER=$DEFAULT_C_COMPILER
 SUDO=$SUDO
+LTO=$LTO
 END
-- 
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