Added gcc lto (Link Time Optimization) option

Just by adding the -flto option to CXXFLAGS link command
we can gain a few percent in speed.

On a Core i5-2500 (3300 Mhz, Sandy Bridge):

64 bit download version:

Without -flto: 1597151 n/s
With -flto : 1659664 n/s

No functional change.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>

diff --git a/src/Makefile b/src/Makefile
index d81e7d707a9c638f3ffe19d513915f1851d07747..0a56e263ee800442434b6baf1ea4a5ad295d8c67 100644 (file)
--- a/src/Makefile
+++ b/src/Makefile
@@ -52,6 +52,7 @@ OBJS = benchmark.o bitbase.o bitboard.o book.o endgame.o evaluate.o main.o \
 # bsfq = no/yes       --- -DUSE_BSFQ  --- Use bsfq x86_64 asm-instruction
 #                                     --- (Works only with GCC and ICC 64-bit)
 # popcnt = no/yes     --- -DUSE_POPCNT --- Use popcnt x86_64 asm-instruction
 # bsfq = no/yes       --- -DUSE_BSFQ  --- Use bsfq x86_64 asm-instruction
 #                                     --- (Works only with GCC and ICC 64-bit)
 # popcnt = no/yes     --- -DUSE_POPCNT --- Use popcnt x86_64 asm-instruction

+# lto = no/yes        --- -flto       --- gcc Link Time Optimization

 #
 # Note that Makefile is space sensitive, so when adding new architectures
 # or modifying existing flags, you have to make sure there are no extra spaces
 #
 # Note that Makefile is space sensitive, so when adding new architectures
 # or modifying existing flags, you have to make sure there are no extra spaces


@@ -123,6 +124,7 @@ ifeq ($(ARCH),x86-64-modern)
        prefetch = yes
        bsfq = yes
        popcnt = yes
        prefetch = yes
        bsfq = yes
        popcnt = yes

+       lto = yes

 endif
 
 ifeq ($(ARCH),x86-32)
 endif
 
 ifeq ($(ARCH),x86-32)


@@ -311,6 +313,14 @@ ifeq ($(popcnt),yes)
        CXXFLAGS += -DUSE_POPCNT
 endif
 
        CXXFLAGS += -DUSE_POPCNT
 endif
 

+### 3.11 lto.
+### Note that this is a mix of compile and link time options
+### because the lto link phase needs access to the optimization flags
+ifeq ($(lto),yes)
+       CXXFLAGS += -flto
+       LDFLAGS += $(CXXFLAGS) -static
+endif
+

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 ### Section 4. Public targets
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 ### Section 4. Public targets
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