RyuJIT doesn't eliminate a jump to the next instruction

[mikedn]

C# code:

using System;

class Program {
    static int Main(string[] args) {
        return Math.Max(args.Length, 42);
    }
}

Generated code:

G_M17764_IG01:

G_M17764_IG02:
       8B4108               mov      eax, dword ptr [rcx+8]
       83F82A               cmp      eax, 42
       7D07                 jge      SHORT G_M17764_IG03
       B82A000000           mov      eax, 42
       EB00                 jmp      SHORT G_M17764_IG03  ;huh???

G_M17764_IG03:
       C3                   ret

category:cq
theme:basic-cq
skill-level:intermediate
cost:medium

[BruceForstall]

We thought we were going to need to generate code between the jmp and the ret, but it turned out to just be "mov eax,eax", so we didn't generate it, but it was too late to get rid of the jmp.

[mikedn]

With if-conversion the following code is generated:

G_M45812_IG01:

G_M45812_IG02:
       8B4108               mov      eax, dword ptr [rcx+8]
       83F82A               cmp      eax, 42
       BA2A000000           mov      edx, 42
       0F4CC2               cmovl    eax, edx

G_M45812_IG03:
       C3                   ret

[BruceForstall]

This still occurs.

LSRA annotates a block that only contains:

         IL_OFFSET void   IL offset: 0x0 REG NA
t10 =    LCL_VAR   int    V03 tmp2         u:1 rax (last use) REG rax $c0
      /--*  t10    int
      *  STORE_LCL_VAR int    V02 tmp1         d:2 rax REG rax

Perhaps it could delete the code? Not really the RA's job, though.

Maybe this is best handled by a peephole optimization.