3 files changed, 40 insertions, 0 deletions
diff --git a/generic/lib/SOURCES b/generic/lib/SOURCES
index f639c83..495b3e7 100644
--- a/generic/lib/SOURCES
+++ b/generic/lib/SOURCES
@@ -8,6 +8,7 @@ integer/abs_diff.cl
 integer/add_sat.cl
 integer/add_sat.ll
 integer/add_sat_impl.ll
+integer/rotate.cl
 integer/sub_sat.cl
 integer/sub_sat.ll
 integer/sub_sat_impl.ll
diff --git a/generic/lib/integer/rotate.cl b/generic/lib/integer/rotate.cl
new file mode 100644
index 0000000..d7eff2b
--- /dev/null
+++ b/generic/lib/integer/rotate.cl
@@ -0,0 +1,4 @@
+#include <clc/clc.h>
+
+#define BODY <rotate.inc>
+#include <clc/integer/gentype.inc>
diff --git a/generic/lib/integer/rotate.inc b/generic/lib/integer/rotate.inc
new file mode 100644
index 0000000..e83dd51
--- /dev/null
+++ b/generic/lib/integer/rotate.inc
@@ -0,0 +1,35 @@
+/**
+ * Not necessarily optimal... but it produces correct results (at least for int)
+ * If we're lucky, LLVM will recognize the pattern and produce rotate
+ * instructions:
+ * http://llvm.1065342.n5.nabble.com/rotate-td47679.html
+ * 
+ * Eventually, someone should feel free to implement an llvm-specific version
+ */
+
+_CLC_OVERLOAD _CLC_DEF GENTYPE rotate(GENTYPE x, GENTYPE n){
+    //Try to avoid extra work if someone's spinning the value through multiple
+    //full rotations
+    n = n % (GENTYPE)GENSIZE;
+    
+    //Determine if we're doing a right or left shift on each component
+    //The actual shift algorithm is based on a rotate right
+    //e.g. a rotate of int by 5 bits becomes rotate right by 26 bits
+    //     and a rotate of int by -4 bits becomes rotate right by 4
+    GENTYPE amt = (n > (GENTYPE)0 ? (GENTYPE)GENSIZE - n : (GENTYPE)0 - n );
+    
+    //Calculate the bits that will wrap
+    GENTYPE mask = ( (GENTYPE)1 << amt ) - (GENTYPE)1;
+    GENTYPE wrapped_bits = x & mask;
+    
+    //Shift the input value right and then AND a mask that eliminates
+    //sign-extension interference
+    //if the rotate amount is 0, just use ~0 for a mask
+    GENTYPE se_mask = !amt ? ~((GENTYPE)0) : 
+        ( ( (GENTYPE)1 << ((GENTYPE)GENSIZE - amt) ) - (GENTYPE)1 );
+    GENTYPE unwrapped_bits = x >> amt;
+    unwrapped_bits &= se_mask;
+    
+    //Finally shift the input right after moving the wrapped bits into position
+    return unwrapped_bits | (wrapped_bits << ( (GENTYPE)GENSIZE - amt ) );
+}
+\ No newline at end of file