From 73c128cf198edd1515a2d392ff05741dba047653 Mon Sep 17 00:00:00 2001
From: Stefan Kerkmann <karlk90@pm.me>
Date: Mon, 7 Feb 2022 22:11:16 +0100
Subject: [PATCH 1/2] [Core] Enable linker relaxation for AVR targets

This can save some bytes for by using RJMP instructions to
memory location that are +-2k relative to the current
program counter position. Unfortunately this is only possible
when LTO is disabled.
---
 platforms/avr/platform.mk | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/platforms/avr/platform.mk b/platforms/avr/platform.mk
index 4d9cafaeef4a..621cd73ba20e 100644
--- a/platforms/avr/platform.mk
+++ b/platforms/avr/platform.mk
@@ -19,6 +19,12 @@ COMPILEFLAGS += -fdata-sections
 COMPILEFLAGS += -fpack-struct
 COMPILEFLAGS += -fshort-enums
 
+# Linker relaxation is only possible if
+# link time optimizations are not enabled.
+ifeq ($(strip $(LTO_ENABLE)), no)
+	COMPILEFLAGS += -mrelax
+endif
+
 ASFLAGS += $(AVR_ASFLAGS)
 
 CFLAGS += $(COMPILEFLAGS) $(AVR_CFLAGS)
@@ -28,7 +34,7 @@ CFLAGS += -fno-strict-aliasing
 CXXFLAGS += $(COMPILEFLAGS)
 CXXFLAGS += -fno-exceptions -std=c++11
 
-LDFLAGS +=-Wl,--gc-sections
+LDFLAGS += -Wl,--gc-sections
 
 OPT_DEFS += -DF_CPU=$(F_CPU)UL
 

From 32dfd75fb1802ae1548bc6b27327981dac49fcd8 Mon Sep 17 00:00:00 2001
From: Stefan Kerkmann <karlk90@pm.me>
Date: Mon, 7 Feb 2022 22:59:08 +0100
Subject: [PATCH 2/2] [Core] Use -mcall-prologues the save code size

From GCC Manual:

Functions prologues/epilogues are expanded as calls
to appropriate subroutines. Code size is smaller.

Small programs with few functions can increase in size,
but QMK benefits from this as it is rather large.

See: https://www.nongnu.org/avr-libc/user-manual/FAQ.html#faq_optflags
---
 platforms/avr/platform.mk | 1 +
 1 file changed, 1 insertion(+)

diff --git a/platforms/avr/platform.mk b/platforms/avr/platform.mk
index 621cd73ba20e..9f304d2e209d 100644
--- a/platforms/avr/platform.mk
+++ b/platforms/avr/platform.mk
@@ -18,6 +18,7 @@ COMPILEFLAGS += -ffunction-sections
 COMPILEFLAGS += -fdata-sections
 COMPILEFLAGS += -fpack-struct
 COMPILEFLAGS += -fshort-enums
+COMPILEFLAGS += -mcall-prologues
 
 # Linker relaxation is only possible if
 # link time optimizations are not enabled.