StringComparer.OrdinalIgnoreCase.Equals is not unrolled for literals

[EgorBo]

bool Foo1(string s) => s.Equals("Test123", StringComparison.OrdinalIgnoreCase);
bool Foo2(string s) => StringComparer.OrdinalIgnoreCase.Equals(s, "Test123");

Codegen:

; Method Pr:Foo1(System.String):bool:this
       cmp      dword ptr [rdx+08H], 7
       jne      SHORT G_M26946_IG04
       mov      rax, 0x20002000200020
       or       rax, qword ptr [rdx+0CH]
       mov      rcx, 0x74007300650074
       xor      rax, rcx
       mov      rdx, qword ptr [rdx+12H]
       or       rdx, 32
       mov      rcx, 0x33003200310074
       xor      rdx, rcx
       or       rax, rdx
       sete     al
       movzx    rax, al
       jmp      SHORT G_M26946_IG05
G_M26946_IG04:
       xor      eax, eax
G_M26946_IG05:
       ret      
; Total bytes of code: 68


; Method Pr:Foo2(System.String):bool:this
       mov      rcx, 0x11097C00308      ; const ptr
       mov      rcx, gword ptr [rcx]
       mov      r8, 0x11080309270      ; 'Test123'
       tail.jmp [System.OrdinalIgnoreCaseComparer:Equals(System.String,System.String):bool:this]
; Total bytes of code: 29

while Foo2 should emit the same optimized/unrolled codegen as Foo1. Should be a simple change.

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Issue Details

---

bool Foo1(string s) => s.Equals("Test123", StringComparison.OrdinalIgnoreCase);
bool Foo2(string s) => StringComparer.OrdinalIgnoreCase.Equals(s, "Test123");

Codegen:

; Method Pr:Foo1(System.String):bool:this
       cmp      dword ptr [rdx+08H], 7
       jne      SHORT G_M26946_IG04
       mov      rax, 0x20002000200020
       or       rax, qword ptr [rdx+0CH]
       mov      rcx, 0x74007300650074
       xor      rax, rcx
       mov      rdx, qword ptr [rdx+12H]
       or       rdx, 32
       mov      rcx, 0x33003200310074
       xor      rdx, rcx
       or       rax, rdx
       sete     al
       movzx    rax, al
       jmp      SHORT G_M26946_IG05
G_M26946_IG04:
       xor      eax, eax
G_M26946_IG05:
       ret      
; Total bytes of code: 68


; Method Pr:Foo2(System.String):bool:this
       mov      rcx, 0x11097C00308      ; const ptr
       mov      rcx, gword ptr [rcx]
       mov      r8, 0x11080309270      ; 'Test123'
       tail.jmp [System.OrdinalIgnoreCaseComparer:Equals(System.String,System.String):bool:this]
; Total bytes of code: 29

while Foo2 should emit the same optimized/unrolled codegen as Foo1. Should be a simple change.

Author:	EgorBo
Assignees:	-
Labels:	area-CodeGen-coreclr
Milestone:	-

[kasperk81]

these is a similar problem with const comparisons which result in false

using System;
public class C
{
    private bool M(string s)
    {
        ArgumentNullException.ThrowIfNull(s);
        return s == "yes";
    }

    public bool Yes() => M("yes");
    public bool No() => M("no");
}

C.Yes()
    L0000: mov eax, 1
    L0005: ret

C.No()
    L0000: mov rax, 0x1dcd6047940
    L000a: mov rax, [rax]
    L000d: mov rdx, 0x1dcd6047948
    L0017: cmp rax, [rdx]
    L001a: je short L001f
    L001c: xor eax, eax
    L001e: ret
    L001f: mov eax, 1
    L0024: jmp short L001e

[EgorBo]

@kasperk81 not an issue in net8 due to frozen objects:

; Method C:Yes():bool:this
       mov      eax, 1
       ret      
; Total bytes of code: 6

; Method C:No():bool:this
       xor      eax, eax
       ret      
; Total bytes of code: 3

[kasperk81]

@EgorBo bravo! crossgen2 results are different https://godbolt.org/z/KTT51eWT1. it's a 14 hours old build 7319f86. and --Os results are worse only for C:No(). oversight?

[EgorBo]

bravo! crossgen2 results are different

We don't use frozen objects in crossgen, only in NativeAOT. It is not trivial (or even possible) to use them in crossgen but it should not matter in most cases since we're going to re-jit R2R anyway.