fix 128bits ctlz intrinsincs UB

[dvermd]

Fixes #604

This is the GIMPLE code generated

      if (param0 == 0) goto then; else goto else;
      then:
      zeros = 128;
      goto after;
      else:
      _2 = param0 >> 64;
      _3 = (size_t) _2;
      if (_3 != 0) goto ctlz_then; else goto ctlz_else;
      after:
      stack_var_1.15_4 = &stack_var_1;
      MEM[(unsigned int *)stack_var_1.15_4] = zeros;
      stack_var_1.16_5 = &stack_var_1;
      loadedValue2 = MEM[(unsigned int *)stack_var_1.16_5];
      D.4444 = loadedValue2;
      return D.4444;
      ctlz_then:
      _6 = param0 >> 64;
      _7 = (size_t) _6;
      _8 = __builtin_clzll (_7);
      zeros = (unsigned int) _8;
      goto ctlz_after;
      ctlz_else:
      _9 = (size_t) param0;
      _10 = __builtin_clzll (_9);
      _11 = (unsigned int) _10;
      zeros = _11 + 64;
      goto ctlz_after;
      ctlz_after:
      zeros = zeros;
      goto after;

[dvermd]

It looks like the some CI jobs are failing on

thread 'rustc' panicked at src/int.rs:176:13:
assertion failed: a_type.dyncast_array().is_some()

which is some code I didn't touch.

Can my changes have some side effects ?
I see that #631 also have these jobs failing. Perhaps it's not my changes which bring these failures.

Any hints ?

[antoyo]

Not sure it's related. I opened a new dummy PR to check if the tests pass, though.

[antoyo]

The CI passed, so the problem is in here.

I suspect this is because you changed the return type: it used to return an array type and your change makes it return a u32.

[dvermd]

The return type of the if width == 128 was already a u32 because the block ended with

                let res = self.context.new_array_access(self.location, result, index);

                return self.gcc_int_cast(res.to_rvalue(), result_type);

which will get an element in the array and cast it as result_type which is u32.

Edit: formatting

[dvermd]

Ok, finally found the line pointing in my change let leading_zeroes = self.add(low_leading_zeroes, sixty_four); where low_leading_zeroesand sixty_four are of different types.

The problem I see is that the if branch should have been taken.