Assertion failed '!"Unexpected tree op after call marked as tailcall"'

[MichalStrehovsky]

Currently failing in main. To repro:

build clr.aot+libs.native+libs.sfx -rc Checked -lc Release
src\tests\build.cmd nativeaot checked tree managed

Then find find the failing ilc.exe command line in the build log if you need it under debugger (look for "exited with code").

JitDump:

dump.txt

Cc @jakobbotsch @EgorBo

[dotnet-policy-service]

Tagging subscribers to this area: @JulieLeeMSFT, @jakobbotsch
See info in area-owners.md if you want to be subscribed.

[jakobbotsch]

We have

------------ BB05 [0005] [000..001) -> BB06(1) (always), preds={BB01} succs={BB06}

***** BB05 [0005]
STMT00006 ( INL01 @ ??? ... ??? ) <- INLRT @ 0x000[E-]
               [000045] DACXG------                         *  STORE_LCL_VAR int    V06 tmp4         
               [000046] --CXG------                         \--*  CALL ind nullcheck int   
               [000047] ----------- this                       +--*  LCL_VAR   byref  V03 tmp1          (last use)
               [000044] ---XG------ gctx                       +--*  IND       long  
               [000043] -----------                            |  \--*  ADD       long  
               [000039] -----------                            |     +--*  SUB       long  
               [000040] -----------                            |     |  +--*  LCL_VAR   long   V05 tmp3         
               [000041] -----------                            |     |  \--*  CNS_INT   long   2
               [000042] -----------                            |     \--*  CNS_INT   long   8
               [000048] ----------- arg2                       +--*  LCL_VAR   ref    V01 arg1          (last use)
               [000038] ---XG------ calli tgt                  \--*  IND       long  
               [000037] -----------                               \--*  SUB       long  
               [000035] -----------                                  +--*  LCL_VAR   long   V05 tmp3          (last use)
               [000036] -----------                                  \--*  CNS_INT   long   2

------------ BB06 [0002] [000..00D) (return), preds={BB04,BB05} succs={}

***** BB06 [0002]
STMT00001 ( 0x000[E-] ... ??? )
               [000014] --C--------                         *  RETURN    int   
               [000023] -----------                         \--*  CAST      int <- ubyte <- int
               [000022] -----------                            \--*  LCL_VAR   int    V06 tmp4          (last use)

and [000046] is marked as a tailcall. That's not legal -- we will lose the truncating cast if we convert it to a tailcall.

It looks exposed by #99265.

[jakobbotsch]

Actually the call has gtReturnType == TYP_UBYTE, so getting rid of the cast is ok. I'll enhance things a bit so inlining doesn't insert the cast in the first place.