Original bug ID: 5592
Reporter: goswin
Status: resolved (set by @gasche on 2012-04-17T18:20:39Z)
Resolution: suspended
Priority: normal
Severity: minor
Version: 3.12.1
Category: back end (clambda to assembly)
Duplicate of: #5541
Related to: #7440
Monitored by: ronan.lehy@gmail.com goswin @hcarty

Bug description

Consider these three functions:

let f1 x y = x = y
let f2 (x:int) y = x = y
let f3 (x:int) y = f1 x y

val f1 : 'a -> 'a -> bool =
val f2 : int -> int -> bool =
val f3 : int -> int -> bool =

One would think that f2 and f3 would generate the same code:

0000000000403550 <camlBaz__f1_1030>:
403550: 48 83 ec 08 sub $0x8,%rsp
403554: 48 89 c7 mov %rax,%rdi
403557: 48 89 de mov %rbx,%rsi
40355a: 48 8b 05 7f 75 21 00 mov 0x21757f(%rip),%rax # 61aa
e0 <_DYNAMIC+0x638>
403561: e8 a6 e2 00 00 callq 41180c <caml_c_call>
403566: 48 83 c4 08 add $0x8,%rsp
40356a: c3 retq
40356b: 0f 1f 44 00 00 nopl 0x0(%rax,%rax,1)

0000000000403570 <camlBaz__f2_1033>:
403570: 48 39 d8 cmp %rbx,%rax
403573: 0f 94 c0 sete %al
403576: 48 0f b6 c0 movzbq %al,%rax
40357a: 48 8d 44 00 01 lea 0x1(%rax,%rax,1),%rax
40357f: c3 retq

0000000000403580 <camlBaz__f3_1036>:
403580: 48 83 ec 08 sub $0x8,%rsp
403584: 48 89 c7 mov %rax,%rdi
403587: 48 89 de mov %rbx,%rsi
40358a: 48 8b 05 4f 75 21 00 mov 0x21754f(%rip),%rax # 61aae0 <_DYNAMIC+0x638>
403591: e8 76 e2 00 00 callq 41180c <caml_c_call>
403596: 48 83 c4 08 add $0x8,%rsp
40359a: c3 retq
40359b: 0f 1f 44 00 00 nopl 0x0(%rax,%rax,1)

But as you can see in f3 the generic polymorphic code from f1 is inlined resulting in a caml_c_call instead of reducing the polymorphism to int and generating the same optimized code as in f2.