diff --git a/src/libruntime/target/stm32f4/abi.S b/src/libruntime/target/stm32f4/abi.S
index 20be117d8..013e0f506 100644
--- a/src/libruntime/target/stm32f4/abi.S
+++ b/src/libruntime/target/stm32f4/abi.S
@@ -53,3 +53,52 @@ __aeabi_llsl:
 
   bx lr
 .end __aeabi_llsl
+
+
+/**
+ * long long __aeabi_llsr(long long {r1, r0}, int {r2})
+ */
+.thumb_func
+.global __aeabi_llsr
+__aeabi_llsr:
+  // if (r2 >= 64) goto 2f;
+  cmp r2, #64
+  bhs 2f
+
+  // if (r2 < 32) goto 1f;
+  cmp r2, #32
+  blo 1f
+
+  // r0 = (r1 >> (r2 - 32));
+  // r1 = 0
+  mov r0, r0
+  sub r2, #32
+  lsr r0, r1, r2
+  mov r1, #0
+
+  bx lr
+  
+  1:
+  // r0 >>= r2
+  lsr r0, r2
+
+  // r0 |= r1 << (32 - r2)
+  mov r3, r1
+  rsb r2, r2, #32
+  lsl r3, r3, r2
+  orr r0, r3
+  rsb r2, r2, #32
+
+  // r1 >>= r2
+  lsr r1, r2
+  
+  bx lr
+
+  2:
+  // r1 = 0;
+  // r0 = 0;
+  mov r1, #0
+  mov r0, #0
+
+  bx lr
+.end __aeabi_llsr