[llvm] [X86][GlobalISel] Add legalization of 64-bit G_ICMP for i686 (PR #69478)

[Evgenii Kudriashov via llvm-commits]

e-kud wrote:

There is a minor change in one test after rebase due to 3fb5b18e81d81d675f8ed57372e2f7ad60a1d548
```
diff --git a/llvm/test/CodeGen/X86/isel-icmp.ll b/llvm/test/CodeGen/X86/isel-icmp.ll
index d6f8fba81ce4..fa5dbaab7e97 100644
--- a/llvm/test/CodeGen/X86/isel-icmp.ll
+++ b/llvm/test/CodeGen/X86/isel-icmp.ll
@@ -168,11 +168,12 @@ define i32 @test_icmp_eq_i64(i64 %a, i64 %b) {
 ; GISEL-X86:       ## %bb.0:
 ; GISEL-X86-NEXT:    movl {{[0-9]+}}(%esp), %eax
 ; GISEL-X86-NEXT:    movl {{[0-9]+}}(%esp), %ecx
+; GISEL-X86-NEXT:    xorl %edx, %edx
 ; GISEL-X86-NEXT:    xorl {{[0-9]+}}(%esp), %eax
 ; GISEL-X86-NEXT:    xorl {{[0-9]+}}(%esp), %ecx
 ; GISEL-X86-NEXT:    orl %eax, %ecx
 ; GISEL-X86-NEXT:    xorl %eax, %eax
-; GISEL-X86-NEXT:    cmpl $0, %ecx
+; GISEL-X86-NEXT:    cmpl %edx, %ecx
 ; GISEL-X86-NEXT:    sete %al
 ; GISEL-X86-NEXT:    andl $1, %eax
 ; GISEL-X86-NEXT:    retl
```

https://github.com/llvm/llvm-project/pull/69478