__udivdi3 and __udivmoddi4 call each other and stuck in loop

[kamleshbhalui]

Summary

currently, call stack is like this

udivdi3 ====> udivmoddi4 ===> udivdi3.
above problem clearly seen when we disabled M extension in RISC-V.
i.e.
00000000000100fc <udivdi3>:

...
10116:       00e000ef          jal  ra,10124 <__udivmoddi4>
...

0000000000010124 <__udivmoddi4>:

...
101a0:       f5dff0ef             jal  ra,100fc <__udivdi3>

to break this loop we provide an independent implementation of __udivdi3.

[MaskRay]

See D77912

[kamleshbhalui]

Replaced by D77912

compiler-rt/lib/builtins/udivdi3.c

 //
 //===----------------------------------------------------------------------===//
 
 #include "int_lib.h"
 
 // Returns: a / b
 
 COMPILER_RT_ABI du_int __udivdi3(du_int a, du_int b) {
-  return __udivmoddi4(a, b, 0);
+  if (b == 0)
+     return -1;
+  du_int result = 0;
+  du_int j = 1;
+  // find max divisor which is less than dividend
+  while (a > b && b < b << 1) {
+    j = j << 1;
+    b = b << 1;
+  }
+  if (a < b) {
+    j = j >> 1;
+    b = b >> 1;
+  }
+  while (j != 0) {
+    if (a >=b ) {
+      a -= b;
+      result |= j;
+    }
+    b = b >> 1;
+    j = j>> 1;
+  }
+  return result;
 }