[Qemu-devel] [5464] Optimize some host-utils function with gcc builtins

[Aurelien Jarno <aurelien@aurel32.net>]

Revision: 5464
          http://svn.sv.gnu.org/viewvc/?view=rev&root=qemu&revision=5464
Author:   aurel32
Date:     2008-10-12 00:53:08 +0000 (Sun, 12 Oct 2008)

Log Message:
-----------
Optimize some host-utils function with gcc builtins

Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>

Modified Paths:
--------------
    trunk/host-utils.h

Modified: trunk/host-utils.h
===================================================================
--- trunk/host-utils.h	2008-10-12 00:52:58 UTC (rev 5463)
+++ trunk/host-utils.h	2008-10-12 00:53:08 UTC (rev 5464)
@@ -47,14 +47,16 @@
 void mulu64(uint64_t *phigh, uint64_t *plow, uint64_t a, uint64_t b);
 #endif
 
-/* Note that some of those functions may end up calling libgcc functions,
-   depending on the host machine. It is up to the target emulation to
-   cope with that. */
-
 /* Binary search for leading zeros.  */
 
 static always_inline int clz32(uint32_t val)
 {
+#if defined(__GNUC__)
+    if (val)
+        return __builtin_clz(val);
+    else
+        return 32;
+#else
     int cnt = 0;
 
     if (!(val & 0xFFFF0000U)) {
@@ -81,6 +83,7 @@
         cnt++;
     }
     return cnt;
+#endif
 }
 
 static always_inline int clo32(uint32_t val)
@@ -90,6 +93,12 @@
 
 static always_inline int clz64(uint64_t val)
 {
+#if defined(__GNUC__)
+    if (val)
+        return __builtin_clzll(val);
+    else
+        return 64;
+#else
     int cnt = 0;
 
     if (!(val >> 32)) {
@@ -99,6 +108,7 @@
     }
 
     return cnt + clz32(val);
+#endif
 }
 
 static always_inline int clo64(uint64_t val)
@@ -108,6 +118,12 @@
 
 static always_inline int ctz32 (uint32_t val)
 {
+#if defined(__GNUC__)
+    if (val)
+        return __builtin_ctz(val);
+    else
+        return 32;
+#else
     int cnt;
 
     cnt = 0;
@@ -136,6 +152,7 @@
      }
 
      return cnt;
+#endif
  }
  
 static always_inline int cto32 (uint32_t val)
@@ -145,6 +162,12 @@
 
 static always_inline int ctz64 (uint64_t val)
 {
+#if defined(__GNUC__)
+    if (val)
+        return __builtin_ctz(val);
+    else
+        return 64;
+#else
     int cnt;
 
     cnt = 0;
@@ -154,6 +177,7 @@
     }
 
     return cnt + ctz32(val);
+#endif
 }
 
 static always_inline int cto64 (uint64_t val)
@@ -182,6 +206,9 @@
 
 static always_inline int ctpop32 (uint32_t val)
 {
+#if defined(__GNUC__)
+    return __builtin_popcount(val);
+#else
     val = (val & 0x55555555) + ((val >>  1) & 0x55555555);
     val = (val & 0x33333333) + ((val >>  2) & 0x33333333);
     val = (val & 0x0f0f0f0f) + ((val >>  4) & 0x0f0f0f0f);
@@ -189,10 +216,14 @@
     val = (val & 0x0000ffff) + ((val >> 16) & 0x0000ffff);
 
     return val;
+#endif
 }
 
 static always_inline int ctpop64 (uint64_t val)
 {
+#if defined(__GNUC__)
+    return __builtin_popcountll(val);
+#else
     val = (val & 0x5555555555555555ULL) + ((val >>  1) & 0x5555555555555555ULL);
     val = (val & 0x3333333333333333ULL) + ((val >>  2) & 0x3333333333333333ULL);
     val = (val & 0x0f0f0f0f0f0f0f0fULL) + ((val >>  4) & 0x0f0f0f0f0f0f0f0fULL);
@@ -201,4 +232,5 @@
     val = (val & 0x00000000ffffffffULL) + ((val >> 32) & 0x00000000ffffffffULL);
 
     return val;
+#endif
 }