1 files changed, 58 insertions, 0 deletions
diff --git a/contrib/compiler-rt/lib/arm/umodsi3.S b/contrib/compiler-rt/lib/arm/umodsi3.S
new file mode 100644
index 000000000000..3a2ab2b87751
--- /dev/null
+++ b/contrib/compiler-rt/lib/arm/umodsi3.S
@@ -0,0 +1,58 @@
+/*===-- umodsi3.S - 32-bit unsigned integer modulus -----------------------===//
+ *
+ *                     The LLVM Compiler Infrastructure
+ *
+ * This file is dual licensed under the MIT and the University of Illinois Open
+ * Source Licenses. See LICENSE.TXT for details.
+ *
+ *===----------------------------------------------------------------------===//
+ *
+ * This file implements the __umodsi3 (32-bit unsigned integer modulus) 
+ * function for the ARM architecture.  A naive digit-by-digit computation is
+ * employed for simplicity.
+ *
+ *===----------------------------------------------------------------------===*/
+
+#include "../assembly.h"
+
+#define a r0
+#define b r1
+#define r r2
+#define i r3
+
+.syntax unified
+.align 3
+DEFINE_COMPILERRT_FUNCTION(__umodsi3)
+//  We use a simple digit by digit algorithm; before we get into the actual 
+//  divide loop, we must calculate the left-shift amount necessary to align
+//  the MSB of the divisor with that of the dividend.
+    clz     r2,     a
+    tst     b,      b       // detect b == 0
+    clz     r3,     b
+    bxeq    lr              // return a if b == 0
+    subs    i,      r3, r2
+    bxlt    lr              // return a if MSB(a) < MSB(b)
+
+LOCAL_LABEL(mainLoop):
+//  This loop basically implements the following:
+//
+//  do {
+//      if (a >= b << i) {
+//          a -= b << i;
+//          if (a == 0) break;
+//      }
+//  } while (--i)
+//
+//  Note that this does not perform the final iteration (i == 0); by doing it
+//  this way, we can merge the two branches which is a substantial win for
+//  such a tight loop on current ARM architectures.
+    subs    r,      a,  b, lsl i
+    movhs   a,      r
+    subsne  i,      i, #1
+    bhi     LOCAL_LABEL(mainLoop)
+
+//  Do the final test subtraction and update of remainder (i == 0), as it is
+//  not performed in the main loop.
+    subs    r,      a,  b
+    movhs   a,      r
+    bx      lr