Extended Description

********** JOINING INTERVALS ***********
entry:
0 %reg1024 = MOV32rm %NOREG, 1, %NOREG, ga:X
4 %reg1025 = MOV32rm <fi#-1>, 1, %NOREG, 0
8 %reg1026 = MOV8rm %reg1024, 1, %NOREG, 0
12 %reg1027 = MOV32rm <fi#-1>, 1, %NOREG, 4
16 %reg1028 = MOV32ri 0
20 %CL = MOV8rr %reg1026
Inspecting %reg1026,0 = [10,46:0) and %reg9,inf =
[22,30:0)[34,42:1): Interference!
24 %reg1029 = MOV32rr %reg1025
Inspecting %reg1025,0 = [6,42:0) and %reg1029,0 =
[26,30:1)[30,58:0): Interference!
28 SHL32rCL %reg1029<def&use>
32 %CL = MOV8rr %reg1026
Inspecting %reg1026,0 = [10,46:0) and %reg9,inf =
[22,30:0)[34,42:1): Interference!
36 %reg1030 = MOV32rr %reg1027
Inspecting %reg1027,0 = [14,38:0) and %reg1030,0 =
[38,42:1)[42,50:0): Joined. Result = %reg1030,0 = [14,42:1)[42,50:0)
40 SHLD32rrCL %reg1030<def&use>, %reg1025

It failed to coalesce reg1026 to CL (reg9):
Inspecting %reg1026,0 = [10,46:0) and %reg9,inf = [22,30:0)[34,42:1): Interference!

The two live ranges are created by copies from the same temp %reg1026.