Rewrite pop_1st_bit() to be endian independent

With this change sources are fully endianess
independent, so we can simplify the Makefile.

Somewhat surprisingly we don't have any speed
regression !

No functional change.

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

diff --git a/src/Makefile b/src/Makefile
index a435066515d947e14d388058a053f6f3d1baa16b..eba72150b614a69de499436d1618bce74cad786b 100644 (file)
--- a/src/Makefile
+++ b/src/Makefile
@@ -47,7 +47,6 @@ OBJS = benchmark.o bitbase.o bitboard.o book.o endgame.o evaluate.o main.o \
 # arch = (name)       --- (-arch)          --- Target architecture
 # os = (name)         ---                  --- Target operating system
 # bits = 64/32        --- -DIS_64BIT       --- 64-/32-bit operating system
-# bigendian = yes/no  --- -DBIGENDIAN      --- big/little-endian byte order
 # prefetch = yes/no   --- -DUSE_PREFETCH   --- Use prefetch x86 asm-instruction
 # bsfq = yes/no       --- -DUSE_BSFQ       --- Use bsfq x86_64 asm-instruction (only
 #                                              with GCC and ICC 64-bit)
@@ -68,7 +67,6 @@ ifeq ($(ARCH),general-64)
        arch = any
        os = any
        bits = 64
-       bigendian = no
        prefetch = no
        bsfq = no
        popcnt = no
@@ -78,27 +76,6 @@ ifeq ($(ARCH),general-32)
        arch = any
        os = any
        bits = 32
-       bigendian = no
-       prefetch = no
-       bsfq = no
-       popcnt = no
-endif
-
-ifeq ($(ARCH),bigendian-64)
-       arch = any
-       os = any
-       bits = 64
-       bigendian = yes
-       prefetch = no
-       bsfq = no
-       popcnt = no
-endif
-
-ifeq ($(ARCH),bigendian-32)
-       arch = any
-       os = any
-       bits = 32
-       bigendian = yes
        prefetch = no
        bsfq = no
        popcnt = no
@@ -109,7 +86,6 @@ ifeq ($(ARCH),x86-64)
        arch = x86_64
        os = any
        bits = 64
-       bigendian = no
        prefetch = yes
        bsfq = yes
        popcnt = no
@@ -119,7 +95,6 @@ ifeq ($(ARCH),x86-64-modern)
        arch = x86_64
        os = any
        bits = 64
-       bigendian = no
        prefetch = yes
        bsfq = yes
        popcnt = yes
@@ -129,7 +104,6 @@ ifeq ($(ARCH),x86-32)
        arch = i386
        os = any
        bits = 32
-       bigendian = no
        prefetch = yes
        bsfq = no
        popcnt = no
@@ -139,7 +113,6 @@ ifeq ($(ARCH),x86-32-old)
        arch = i386
        os = any
        bits = 32
-       bigendian = no
        prefetch = no
        bsfq = no
        popcnt = no
@@ -150,7 +123,6 @@ ifeq ($(ARCH),osx-ppc-64)
        arch = ppc64
        os = osx
        bits = 64
-       bigendian = yes
        prefetch = no
        bsfq = no
        popcnt = no
@@ -160,7 +132,6 @@ ifeq ($(ARCH),osx-ppc-32)
        arch = ppc
        os = osx
        bits = 32
-       bigendian = yes
        prefetch = no
        bsfq = no
        popcnt = no
@@ -170,7 +141,6 @@ ifeq ($(ARCH),osx-x86-64)
        arch = x86_64
        os = osx
        bits = 64
-       bigendian = no
        prefetch = yes
        bsfq = yes
        popcnt = no
@@ -180,7 +150,6 @@ ifeq ($(ARCH),osx-x86-32)
        arch = i386
        os = osx
        bits = 32
-       bigendian = no
        prefetch = yes
        bsfq = no
        popcnt = no
@@ -293,12 +262,7 @@ ifeq ($(bits),64)
        CXXFLAGS += -DIS_64BIT
 endif
 
-### 3.7 Endianess
-ifeq ($(bigendian),yes)
-       CXXFLAGS += -DBIGENDIAN
-endif
-
-### 3.8 prefetch
+### 3.7 prefetch
 ifeq ($(prefetch),yes)
        CXXFLAGS += -msse
        DEPENDFLAGS += -msse
@@ -306,17 +270,17 @@ else
        CXXFLAGS += -DNO_PREFETCH
 endif
 
-### 3.9 bsfq
+### 3.8 bsfq
 ifeq ($(bsfq),yes)
        CXXFLAGS += -DUSE_BSFQ
 endif
 
-### 3.10 popcnt
+### 3.9 popcnt
 ifeq ($(popcnt),yes)
        CXXFLAGS += -msse3 -DUSE_POPCNT
 endif
 
-### 3.11 Link Time Optimization, it works since gcc 4.5 but not on mingw.
+### 3.10 Link Time Optimization, it works since gcc 4.5 but not on mingw.
 ### This is a mix of compile and link time options because the lto link phase
 ### needs access to the optimization flags.
 ifeq ($(comp),gcc)
@@ -359,8 +323,6 @@ help:
        @echo "osx-x86-32           > x86-Mac OS X 32 bit"
        @echo "general-64           > unspecified 64-bit"
        @echo "general-32           > unspecified 32-bit"
-       @echo "bigendian-64         > unspecified 64-bit with bigendian byte order"
-       @echo "bigendian-32         > unspecified 32-bit with bigendian byte order"
        @echo ""
        @echo "Supported comps:"
        @echo ""
@@ -433,7 +395,6 @@ config-sanity:
        @echo "arch: '$(arch)'"
        @echo "os: '$(os)'"
        @echo "bits: '$(bits)'"
-       @echo "bigendian: '$(bigendian)'"
        @echo "prefetch: '$(prefetch)'"
        @echo "bsfq: '$(bsfq)'"
        @echo "popcnt: '$(popcnt)'"
@@ -451,7 +412,6 @@ config-sanity:
         test "$(arch)" = "ppc64" || test "$(arch)" = "ppc"
        @test "$(os)" = "any" || test "$(os)" = "osx"
        @test "$(bits)" = "32" || test "$(bits)" = "64"
-       @test "$(bigendian)" = "yes" || test "$(bigendian)" = "no"
        @test "$(prefetch)" = "yes" || test "$(prefetch)" = "no"
        @test "$(bsfq)" = "yes" || test "$(bsfq)" = "no"
        @test "$(popcnt)" = "yes" || test "$(popcnt)" = "no"
@@ -507,7 +467,7 @@ icc-profile-clean:
 
 hpux:
        $(MAKE) \
-       CXX='/opt/aCC/bin/aCC -AA +hpxstd98 -DBIGENDIAN -mt +O3 -DNDEBUG -DNO_PREFETCH' \
+       CXX='/opt/aCC/bin/aCC -AA +hpxstd98 -mt +O3 -DNDEBUG -DNO_PREFETCH' \
        CXXFLAGS="" \
        LDFLAGS="" \
        all

diff --git a/src/bitboard.cpp b/src/bitboard.cpp
index 321055e826dba25609ab2ce00e0f5743080fcca7..40cdbb21ff956601238b0db0dc72176e5cb081cb 100644 (file)
--- a/src/bitboard.cpp
+++ b/src/bitboard.cpp
@@ -92,33 +92,13 @@ Square first_1(Bitboard b) {
   return Square(BSFTable[(fold * 0x783A9B23) >> 26]);
 }
 
-// Use type-punning
-union b_union {
-
-    Bitboard dummy;
-    struct {
-#if defined (BIGENDIAN)
-        uint32_t h;
-        uint32_t l;
-#else
-        uint32_t l;
-        uint32_t h;
-#endif
-    } b;
-};
-
 Square pop_1st_bit(Bitboard* b) {
 
-   const b_union u = *((b_union*)b);
-
-   if (u.b.l)
-   {
-       ((b_union*)b)->b.l = u.b.l & (u.b.l - 1);
-       return Square(BSFTable[((u.b.l ^ (u.b.l - 1)) * 0x783A9B23) >> 26]);
-   }
-
-   ((b_union*)b)->b.h = u.b.h & (u.b.h - 1);
-   return Square(BSFTable[((~(u.b.h ^ (u.b.h - 1))) * 0x783A9B23) >> 26]);
+  Bitboard bb = *b;
+  *b = bb & (bb - 1);
+  bb ^= (bb - 1);
+  uint32_t fold = unsigned(bb) ^ unsigned(bb >> 32);
+  return Square(BSFTable[(fold * 0x783A9B23) >> 26]);
 }
 
 Square last_1(Bitboard b) {