[tip:tools/kvm] kvm tools: only enable LTO if supported by GCC

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Commit-ID:  cf277dc3d0a471eeaccf5dde4f9a74fc37b09814
Gitweb:     http://git.kernel.org/tip/cf277dc3d0a471eeaccf5dde4f9a74fc37b09814
Author:     Will Deacon <will.deacon@xxxxxxx>
AuthorDate: Mon, 12 Nov 2012 11:57:16 +0000
Committer:  Pekka Enberg <penberg@xxxxxxxxxx>
CommitDate: Tue, 13 Nov 2012 09:23:00 +0200

kvm tools: only enable LTO if supported by GCC

Commit 99423f12db2a ("kvm tools: enable LTO") unconditionally enabled
link-time-optimisations when building kvmtool. Unfortunately, passing
-flto to a GCC without support for the option, results in a fatal build
error:

  cc1: error: LTO support has not been enabled in this configuration

This patch adds a check to the kvm tools Makefile so that LTO is only
enabled if the host compiler supports it.

Signed-off-by: Will Deacon <will.deacon@xxxxxxx>
Signed-off-by: Pekka Enberg <penberg@xxxxxxxxxx>
---
 tools/kvm/Makefile | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/tools/kvm/Makefile b/tools/kvm/Makefile
index f12e587..23a7c40 100644
--- a/tools/kvm/Makefile
+++ b/tools/kvm/Makefile
@@ -226,6 +226,11 @@ ifeq ($(call try-cc,$(SOURCE_AIO),$(FLAGS_AIO) -static),y)
 	LIBS_STATOPT	+= -laio
 endif
 
+FLAGS_LTO := -flto
+ifeq ($(call try-cc,$(SOURCE_HELLO),$(FLAGS_LTO)),y)
+	CFLAGS		+= $(FLAGS_LTO)
+endif
+
 ifneq ($(call try-build,$(SOURCE_STATIC),-static,),y)
 $(error No static libc found. Please install glibc-static package.)
 endif
@@ -244,7 +249,7 @@ DEFINES	+= -DKVMTOOLS_VERSION='"$(KVMTOOLS_VERSION)"'
 DEFINES	+= -DBUILD_ARCH='"$(ARCH)"'
 
 KVM_INCLUDE := include
-CFLAGS	+= $(CPPFLAGS) $(DEFINES) -I$(KVM_INCLUDE) -I$(ARCH_INCLUDE) -I$(KINCL_PATH)/include/uapi -I$(KINCL_PATH)/include -I$(KINCL_PATH)/arch/$(ARCH)/include/uapi -I$(KINCL_PATH)/arch/$(ARCH)/include/ -O2 -fno-strict-aliasing -g -flto
+CFLAGS	+= $(CPPFLAGS) $(DEFINES) -I$(KVM_INCLUDE) -I$(ARCH_INCLUDE) -I$(KINCL_PATH)/include/uapi -I$(KINCL_PATH)/include -I$(KINCL_PATH)/arch/$(ARCH)/include/uapi -I$(KINCL_PATH)/arch/$(ARCH)/include/ -O2 -fno-strict-aliasing -g
 
 WARNINGS += -Wall
 WARNINGS += -Wcast-align
--
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