[ocaml.tailcall] is wrong for functions with more than 10 arguments (in Mach). #10424
Description
Consider:
let rec h x1 x2 x3 x4 x5 x6 x7 x8 x9 x10 x11 =
if x1 = 0 then
0
else
(i [@ocaml.tailcall]) (x1 - 1) x2 x3 x4 x5 x6 x7 x8 x9 x10 x11
and i x1 x2 x3 x4 x5 x6 x7 x8 x9 x10 x11 =
(h [@ocaml.tailcall]) x1 x2 x3 x4 x5 x6 x7 x8 x9 x10 x11This code is accepted by the compiler even when "Warning 51" is enabled.
However, when looking at its mach representation, the first call to i is not a tailcall:
camlBar__h_81(R/0[%rax] R/1[%rbx] R/2[%rdi] R/3[%rsi] R/4[%rdx] R/5[%rcx] R/6[%r8] R/7[%r9] R/8[%r12] R/9[%r13] R/40[si0]) {bar.ml:1,10-147}
x1/29 := R/0[%rax]
x2/30 := R/1[%rbx]
x3/31 := R/2[%rdi]
x4/32 := R/3[%rsi]
x5/33 := R/4[%rdx]
x6/34 := R/5[%rcx]
x7/35 := R/6[%r8]
x8/36 := R/7[%r9]
x9/37 := R/8[%r12]
x10/38 := R/9[%r13]
x11/39 := R/40[si0]
if x1/29 ==s 1 then
I/45 := 1
R/0[%rax] := I/45
return R/0[%rax]
else
I/41 := x1/29
I/41 := I/41 + -2{bar.ml:5,30-38}
offset stack 16
R/0[%rax] := I/41
R/1[%rbx] := x2/30
R/2[%rdi] := x3/31
R/3[%rsi] := x4/32
R/4[%rdx] := x5/33
R/5[%rcx] := x6/34
R/6[%r8] := x7/35
R/7[%r9] := x8/36
R/8[%r12] := x9/37
R/9[%r13] := x10/38
R/43[so0] := x11/39
R/0[%rax] := call "camlBar__i_82" R/0[%rax] R/1[%rbx] R/2[%rdi] R/3[%rsi] R/4[%rdx] R/5[%rcx] R/6[%r8] R/7[%r9] R/8[%r12] R/9[%r13] R/43[so0]{bar.ml:5,8-70}
offset stack -16
V/42 := R/0[%rax]
I/44 := V/42
I/44 := I/44 + 2{bar.ml:5,4-70}
R/0[%rax] := I/44
return R/0[%rax]
endif
Tested with trunk, 4.10.2, and 4.12.0.