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LLVM backend for 6502
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ce7cafa960
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Chris Lattner ce7cafa960 shld is a very high latency operation. Instead of emitting it for shifts of 
two or three, open code the equivalent operation which is faster on athlon
and P4 (by a substantial margin).

For example, instead of compiling this:

long long X2(long long Y) { return Y << 2; }

to:

X3_2:
        movl 4(%esp), %eax
        movl 8(%esp), %edx
        shldl $2, %eax, %edx
        shll $2, %eax
        ret

Compile it to:

X2:
        movl 4(%esp), %eax
        movl 8(%esp), %ecx
        movl %eax, %edx
        shrl $30, %edx
        leal (%edx,%ecx,4), %edx
        shll $2, %eax
        ret

Likewise, for << 3, compile to:

X3:
        movl 4(%esp), %eax
        movl 8(%esp), %ecx
        movl %eax, %edx
        shrl $29, %edx
        leal (%edx,%ecx,8), %edx
        shll $3, %eax
        ret

This matches icc, except that icc open codes the shifts as adds on the P4.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@17707 91177308-0d34-0410-b5e6-96231b3b80d8
2004-11-13 20:48:57 +00:00
autoconf Add the RUNTEST autoconf onfiguration variable for Deja-gnu support. This 2004-11-07 23:29:39 +00:00
docs Document the new llvm-ranlib command. 2004-11-12 00:18:35 +00:00
examples Clean up code layout, delete extra blank line, say fibonacci' instead of foo' 2004-11-05 04:11:40 +00:00
include/llvm Add support for shifts 2004-11-13 19:32:45 +00:00
lib shld is a very high latency operation. Instead of emitting it for shifts of 2004-11-13 20:48:57 +00:00
projects Change macro names per naming standard in Makefile.rules. 2004-10-30 09:26:22 +00:00
runtime Internalize variable names to prevent recursive assignment. Cleanup docs. 2004-10-30 09:19:36 +00:00
test New testcase 2004-11-13 19:49:39 +00:00
tools Make sure llee can deal with compressed bytecode too. 2004-11-09 20:21:25 +00:00
utils * Add support for f2c and the -f2c switch to enable Fortran benchmarks 2004-11-08 03:28:27 +00:00
win32 This file is gone 2004-11-08 18:46:09 +00:00
.cvsignore
configure Add the RUNTEST autoconf onfiguration variable for Deja-gnu support. This 2004-11-07 23:29:39 +00:00
CREDITS.TXT
LICENSE.TXT
llvm.spec
llvm.spec.in
Makefile Move path override in test/Makefile. 2004-11-08 05:44:05 +00:00
Makefile.common No really, this is LLVM! 2004-10-30 00:57:52 +00:00
Makefile.config.in Add the RUNTEST autoconf onfiguration variable for Deja-gnu support. This 2004-11-07 23:29:39 +00:00
Makefile.rules * Clean up all the shared library output on uninstall 2004-11-12 02:27:36 +00:00
README.txt

README.txt 

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================================

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