LoadIC_Miss builtin receives parameters on registers (see LoadWithVectorDescriptor) and tail
calls to Runtime::LoadIC_Miss.

This is how LoadIC_Miss builtin generated by CSA look like on x64 (same issues on ia32):

 0  4883ec20       REX.W subq rsp,0x20
 4  4c8b542420     REX.W movq r10,[rsp+0x20]
 9  4c891424       REX.W movq [rsp],r10
13  4889542420     REX.W movq [rsp+0x20],rdx
18  48894c2418     REX.W movq [rsp+0x18],rcx
23  4889442410     REX.W movq [rsp+0x10],rax
28  48895c2408     REX.W movq [rsp+0x8],rbx
33  48bbb0dec00100000000 REX.W movq rbx,0x1c0deb0    ;; external reference (Runtime::LoadIC_Miss)
43  b804000000     movl rax,0x4
48  4c8bc3         REX.W movq r8,rbx
51  488bf8         REX.W movq rdi,rax
54  e9250cfdff     jmp 0x1d9f49e062c0      ;; code: STUB, CEntryStub, minor: 4
59  0f0b           ud2
61  0f1f00         nop

I see two issues:
1) The instructions 48-51 are unexpected here.
2) The sequence 0-28 could probably be generated in a nicer way. This is how hand-written code looks like:

 0  5f             pop rdi
 1  52             push rdx
 2  51             push rcx
 3  50             push rax
 4  53             push rbx
 5  57             push rdi
 6  b804000000     movl rax,0x4
11  48bb4071bf0100000000 REX.W movq rbx,0x1bf7140    ;; external reference (Runtime::LoadIC_Miss)
21  e96620fdff     jmp 0x3a47f02075c0      ;; code: STUB, CEntryStub, minor: 4



To reproduce, add this code to any cctest.

TEST(Dump) {
  Isolate* isolate(CcTest::InitIsolateOnce());
  isolate->builtins()->LoadIC_Miss()->Print();
  isolate->builtins()->LoadIC_Slow()->Print();
}


CCing Mircea as (1) could be a register allocator issue.