[Issue 18461] core.bitop.bt returns garbage in release code

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=18461

bitter.taste at gmx.com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |bitter.taste at gmx.com
          Component|phobos                      |dmd

--- Comment #9 from bitter.taste at gmx.com ---
This is a (major?) codegen bug in dmd, the joint action of -inline and -release
makes the rmdeadass kill the `test_val' definition and fold the argument `p' of
the `bt' function into `&test_val': that's right, the variable is gone but the
reference to it is still there, leading to the generation of the silly `lea'
instruction pointing into the stack.

Some more details for the lovers of the gory details:

```
ambiguous lvalue: test_val(0) =  16LL 
assnod[0]: test_val(0) =  16LL 
        POSS
        DEAD=0, live=0
dead assignment (test_val(0) =  16LL ) Boutlv
elimass
el:0x55687ec1d360 cnt=0 =  TYuns long long 0x55687ec1d170 0x55687ec1d300
 el:0x55687ec1d170 cnt=0 var  TYuns long long  test_val
 el:0x55687ec1d300 cnt=0 const  TYuns long long 16LL 
assnod[1]: p(1) =  #test_val(0)
        POSS
        DEAD=0, live=0
dead assignment (p(1) =  #test_val(0)) Boutlv
elimass
el:0x55687ec1d9f0 cnt=0 =  mTYconst|TY* 0x55687ec1d810 0x55687ec1d8d0
 el:0x55687ec1d810 cnt=0 var  mTYconst|TY*  p
 el:0x55687ec1d8d0 cnt=0 relconst  TY*  0+& test_val
assnod[2]: bitnum(2) =  4LL 
        POSS
        DEAD=0, live=0
dead assignment (bitnum(2) =  4LL ) Boutlv
elimass
el:0x55687ec1dcc0 cnt=0 =  TYuns long long 0x55687ec1dba0 0x55687ec1dc60
 el:0x55687ec1dba0 cnt=0 var  TYuns long long  bitnum
 el:0x55687ec1dc60 cnt=0 const  TYuns long long 4LL 
```

If I understand correctly what's going on the variables are killed even though
they're not dead because they don't escape the block (they're not in Boutlv).

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