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Redundant bounds check #121259
Description
The following snippet produces a redundant bounds check:
void Test(ReadOnlySpan<char> name)
{
int length = name.Length;
if (length == 0)
{
return;
}
if (length == 1)
{
if (name[0] == ':')
{
return;
}
}
else if (name[0] == ':' && name[1] != ':')
{
return;
}
}Codegen:
; Method Program:Test(System.ReadOnlySpan`1[char]):this (FullOpts)
sub rsp, 40
mov rax, bword ptr [rdx]
mov ecx, dword ptr [rdx+0x08]
test ecx, ecx
je SHORT G_M56625_IG05
cmp ecx, 1
je SHORT G_M56625_IG04
cmp word ptr [rax], 58
jne SHORT G_M56625_IG05
cmp ecx, 1
jbe SHORT G_M56625_IG06
jmp SHORT G_M56625_IG05
G_M56625_IG04:
cmp word ptr [rax], ax
G_M56625_IG05:
add rsp, 40
ret
G_M56625_IG06:
call CORINFO_HELP_RNGCHKFAIL
int3
; Total bytes of code: 46It's actually a simplified version of:
if (name is [] or [':'] or [':', not ':', ..])
{
}Reacted by Paulus Pärssinen
Activity
dotnet-policy-service commentedon Nov 1, 2025
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