From 87e387acd8eba5021a8e5d6b54e0c5ef5c28ada2 Mon Sep 17 00:00:00 2001
From: Stafford Horne <shorne@gmail.com>
Date: Sat, 22 Jan 2022 13:32:38 +0900
Subject: openrisc: Add gcc machine instruction flag configuration

OpenRISC GCC supports flags to enable the backend to output instructions
if they are supported by a target processor.  This patch adds
configuration flags to enable configuring these flags to tune the kernel
for a particular CPU configuration.

In the future we could also enable all of these flags by default and
provide instruction emulation in the kernel to make these choices easier
for users but this is what we provide for now.

Signed-off-by: Stafford Horne <shorne@gmail.com>
---
 arch/openrisc/Kconfig  | 53 ++++++++++++++++++++++++++++++++++++++++++++++++++
 arch/openrisc/Makefile | 17 ++++++++++++++++
 2 files changed, 70 insertions(+)

(limited to 'arch/openrisc')

diff --git a/arch/openrisc/Kconfig b/arch/openrisc/Kconfig
index 0d68adf6e02b..37243f023805 100644
--- a/arch/openrisc/Kconfig
+++ b/arch/openrisc/Kconfig
@@ -114,6 +114,59 @@ config OPENRISC_HAVE_INST_DIV
 	default y
 	help
 	  Select this if your implementation has a hardware divide instruction
+
+config OPENRISC_HAVE_INST_CMOV
+	bool "Have instruction l.cmov for conditional move"
+	default n
+	help
+	  This config enables gcc to generate l.cmov instructions when compiling
+	  the kernel which in general will improve performance and reduce the
+	  binary size.
+
+	  Select this if your implementation has support for the Class II
+	  l.cmov conistional move instruction.
+
+	  Say N if you are unsure.
+
+config OPENRISC_HAVE_INST_ROR
+	bool "Have instruction l.ror for rotate right"
+	default n
+	help
+	  This config enables gcc to generate l.ror instructions when compiling
+	  the kernel which in general will improve performance and reduce the
+	  binary size.
+
+	  Select this if your implementation has support for the Class II
+	  l.ror rotate right instruction.
+
+	  Say N if you are unsure.
+
+config OPENRISC_HAVE_INST_RORI
+	bool "Have instruction l.rori for rotate right with immediate"
+	default n
+	help
+	  This config enables gcc to generate l.rori instructions when compiling
+	  the kernel which in general will improve performance and reduce the
+	  binary size.
+
+	  Select this if your implementation has support for the Class II
+	  l.rori rotate right with immediate instruction.
+
+	  Say N if you are unsure.
+
+config OPENRISC_HAVE_INST_SEXT
+	bool "Have instructions l.ext* for sign extension"
+	default n
+	help
+	  This config enables gcc to generate l.ext* instructions when compiling
+	  the kernel which in general will improve performance and reduce the
+	  binary size.
+
+	  Select this if your implementation has support for the Class II
+	  l.exths, l.extbs, l.exthz and l.extbz size extend instructions.
+
+	  Say N if you are unsure.
+
 endmenu
 
 config NR_CPUS
diff --git a/arch/openrisc/Makefile b/arch/openrisc/Makefile
index 760b734fb822..b446510173cd 100644
--- a/arch/openrisc/Makefile
+++ b/arch/openrisc/Makefile
@@ -21,6 +21,7 @@ OBJCOPYFLAGS    := -O binary -R .note -R .comment -S
 LIBGCC 		:= $(shell $(CC) $(KBUILD_CFLAGS) -print-libgcc-file-name)
 
 KBUILD_CFLAGS	+= -pipe -ffixed-r10 -D__linux__
+KBUILD_CFLAGS	+= -msfimm -mshftimm
 
 all: vmlinux.bin
 
@@ -38,6 +39,22 @@ else
 	KBUILD_CFLAGS += $(call cc-option,-msoft-div)
 endif
 
+ifeq ($(CONFIG_OPENRISC_HAVE_INST_CMOV),y)
+	KBUILD_CFLAGS += $(call cc-option,-mcmov)
+endif
+
+ifeq ($(CONFIG_OPENRISC_HAVE_INST_ROR),y)
+	KBUILD_CFLAGS += $(call cc-option,-mror)
+endif
+
+ifeq ($(CONFIG_OPENRISC_HAVE_INST_RORI),y)
+	KBUILD_CFLAGS += $(call cc-option,-mrori)
+endif
+
+ifeq ($(CONFIG_OPENRISC_HAVE_INST_SEXT),y)
+	KBUILD_CFLAGS += $(call cc-option,-msext)
+endif
+
 head-y 		:= arch/openrisc/kernel/head.o
 
 libs-y		+= $(LIBGCC)
-- 
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