Loop is not cloned for partial array iteration

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#118,800 2 comments 0 reactions 1 assignee View on GitHub

@EgorBo is already working on this.

Since Aug 15, 2025.

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This issue has not been assessed yet.

Description

area-CodeGen-coreclr 
static int SumARange1(int[] array, int offset, int count)
{
    int sum = 0;
    for (int i = offset; i < offset + count; i++)
        sum += array[i];
    return sum;
}

Current codegen:

; Method Test_DevDiv_255294:SumARange1(int[],int,int):int (FullOpts)
       sub      rsp, 40
       xor      eax, eax
       mov      r10d, edx
       add      r8d, r10d
       cmp      r8d, edx
       jle      SHORT G_M48878_IG05
       mov      edx, dword ptr [rcx+0x08]
       align    [12 bytes for IG04]
G_M48878_IG04:
       cmp      r10d, edx
       jae      SHORT G_M48878_IG06
       add      eax, dword ptr [rcx+4*r10+0x10]
       inc      r10d
       cmp      r8d, r10d
       jg       SHORT G_M48878_IG04
G_M48878_IG05:
       add      rsp, 40
       ret      
G_M48878_IG06:
       call     CORINFO_HELP_RNGCHKFAIL
       int3     
; Total bytes of code: 61

While it's not legal to drop the bounds check here, JIT should be able to handle it via loop cloning.

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