LLVM backend for 6502
Go to file
Chris Lattner b6bac51351 * Make the previous patch more efficient by not allocating a temporary MachineInstr
to do analysis.

*** FOLD getelementptr instructions into loads and stores when possible,
    making use of some of the crazy X86 addressing modes.

For example, the following C++ program fragment:

struct complex {
    double re, im;
    complex(double r, double i) : re(r), im(i) {}
};
inline complex operator+(const complex& a, const complex& b) {
    return complex(a.re+b.re, a.im+b.im);
}
complex addone(const complex& arg) {
    return arg + complex(1,0);
}

Used to be compiled to:
_Z6addoneRK7complex:
        mov %EAX, DWORD PTR [%ESP + 4]
        mov %ECX, DWORD PTR [%ESP + 8]
***     mov %EDX, %ECX
        fld QWORD PTR [%EDX]
        fld1
        faddp %ST(1)
***     add %ECX, 8
        fld QWORD PTR [%ECX]
        fldz
        faddp %ST(1)
***     mov %ECX, %EAX
        fxch %ST(1)
        fstp QWORD PTR [%ECX]
***     add %EAX, 8
        fstp QWORD PTR [%EAX]
        ret

Now it is compiled to:
_Z6addoneRK7complex:
        mov %EAX, DWORD PTR [%ESP + 4]
        mov %ECX, DWORD PTR [%ESP + 8]
        fld QWORD PTR [%ECX]
        fld1
        faddp %ST(1)
        fld QWORD PTR [%ECX + 8]
        fldz
        faddp %ST(1)
        fxch %ST(1)
        fstp QWORD PTR [%EAX]
        fstp QWORD PTR [%EAX + 8]
        ret

Other programs should see similar improvements, across the board.  Note that
in addition to reducing instruction count, this also reduces register pressure
a lot, always a good thing on X86.  :)


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@11819 91177308-0d34-0410-b5e6-96231b3b80d8
2004-02-25 06:13:04 +00:00
autoconf small portability fix. 2004-02-24 22:58:31 +00:00
docs Fixed minor typos. 2004-02-24 16:13:56 +00:00
examples/ModuleMaker
include Cygwin defines log2 as a macro. Undef it here IFF it has already been defined, 2004-02-25 01:53:45 +00:00
lib * Make the previous patch more efficient by not allocating a temporary MachineInstr 2004-02-25 06:13:04 +00:00
projects Remove dependence on the return type of ConstantArray::get 2004-02-15 04:05:58 +00:00
runtime Build an archive for use with Povray. 2004-02-20 21:26:46 +00:00
test New testcase. Switch instructions that go to switch instructions should be 2004-02-24 07:21:09 +00:00
tools Include Config/config.h for SHLIBEXT. 2004-02-23 22:42:51 +00:00
utils Add a label for the bump when we started counting llvm/projects 2004-02-18 20:27:06 +00:00
.cvsignore
configure Added the VTune tests. 2004-02-24 21:43:38 +00:00
CREDITS.TXT
LICENSE.TXT we no longer include boost 2004-02-24 04:02:20 +00:00
llvm.spec RPM spec file for LLVM tools and libraries. 2004-02-10 03:57:51 +00:00
llvm.spec.in RPM spec file for LLVM tools and libraries. 2004-02-10 03:57:51 +00:00
Makefile Should fix pr220 - "make install" doesn't install header files when 2004-02-10 01:10:01 +00:00
Makefile.common
Makefile.config.in Added the POVRAY_ROOT to locate Povray. 2004-02-20 22:30:46 +00:00
Makefile.rules Define DEPRECATED so that it can be used in function and variable 2004-02-13 20:05:44 +00:00
README.txt

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----------------
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