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Add optimization to Target/README.txt.

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llvm-svn: 110543
This commit is contained in:
Nick Lewycky 2010-08-08 07:04:25 +00:00
parent 0651189df1
commit 3a15ba4d5e
1 changed files with 17 additions and 1 deletions
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18
lib/Target/README.txt
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@ -1919,5 +1919,21 @@ something like the following, which eliminates a branch:
ret
.LBB0_2:
jmp foo # TAILCALL
//===---------------------------------------------------------------------===//
Given a branch where the two target blocks are identical ("ret i32 %b" in
both), simplifycfg will simplify them away. But not so for a switch statement:
define i32 @f(i32 %a, i32 %b) nounwind readnone {
entry:
switch i32 %a, label %bb3 [
i32 4, label %bb
i32 6, label %bb
]
bb: ; preds = %entry, %entry
ret i32 %b
bb3: ; preds = %entry
ret i32 %b
}
//===---------------------------------------------------------------------===//