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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@34101 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2007-02-09 17:38:01 +00:00
parent fd57a00972
commit 8abcfe11b5
1 changed files with 29 additions and 0 deletions
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29
lib/Target/PowerPC/README.txt
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@ -596,3 +596,32 @@ _test:
This sort of thing occurs a lot due to globalopt.
===-------------------------------------------------------------------------===
We currently compile 32-bit bswap:
declare i32 @llvm.bswap.i32(i32 %A)
define i32 @test(i32 %A) {
%B = call i32 @llvm.bswap.i32(i32 %A)
ret i32 %B
}
to:
_test:
rlwinm r2, r3, 24, 16, 23
slwi r4, r3, 24
rlwimi r2, r3, 8, 24, 31
rlwimi r4, r3, 8, 8, 15
rlwimi r4, r2, 0, 16, 31
mr r3, r4
blr
it would be more efficient to produce:
_foo: mr r0,r3
rlwinm r3,r3,8,0xffffffff
rlwimi r3,r0,24,0,7
rlwimi r3,r0,24,16,23
blr
===-------------------------------------------------------------------------===