[LLVMbugs] [Bug 535] NEW: Register allocator should remove unnecessary copies

[bugzilla-daemon at cs.uiuc.edu]

http://llvm.cs.uiuc.edu/bugs/show_bug.cgi?id=535

           Summary: Register allocator should remove unnecessary copies
           Product: libraries
           Version: trunk
          Platform: DEC
        OS/Version: Linux
            Status: NEW
          Severity: enhancement
          Priority: P2
         Component: Register Allocator
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: alenhar2 at uiuc.edu


$29 is involved in 3 unnecessary copies.  

llc -print-machineinstrs ex_spill.bc -march=alpha
# Machine code for foo():

 (0x120fa8b50, LLVM BB @0x120fa3120):
        %$16 = IDEF
        %$29 = IDEF
        %reg1025 = BIS %$29, %$29
        %reg1026 = BIS %$16, %$16
        %reg1027 = BIS %reg1026, %reg1026
        %reg1028 = LOAD_IMM 5
        %$29 = BIS %reg1025, %reg1025
        STL_SYM %reg1028, <ga:MyVar>
        %reg1029 = LOAD_IMM 12
        %$29 = BIS %reg1025, %reg1025
        STL_SYM %reg1029, <ga:MyVar2>
        %reg1030 = LOAD_IMM 0
        %$0 = BIS %reg1030, %reg1030
        RETURN

# End machine code for foo().

# Machine code for foo():

 (0x120fa8b50, LLVM BB @0x120fa3120):
        %$16 = IDEF
        %$29 = IDEF
        %$0 = BIS %$29, %$29
        %$1 = LOAD_IMM 5
        %$29 = BIS %$0, %$0
        STL_SYM %$1, <ga:MyVar>
        %$1 = LOAD_IMM 12
        %$29 = BIS %$0, %$0
        STL_SYM %$1, <ga:MyVar2>
        %$0 = LOAD_IMM 0
        RETURN

# End machine code for foo().



Here is the .ll file:

%MyVar     = uninitialized global int
%MyVar2    = uninitialized global int

implementation

int "foo"(int %blah)
begin
        store int 5, int *%MyVar
        store int 12, int* %MyVar2
        ret int 0
end



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