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implement a transformation in jump threading that is currently

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done by condprop, but do it in a much more general form.  The
basic idea is that we can do a limited form of tail duplication
in the case when we have a branch on a phi.  Moving the branch
up in to the predecessor block makes instruction selection
much easier and encourages chained jump threadings.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@83759 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner
2009-10-11 07:24:57 +00:00
parent 113e4c6070
commit 78c552ef30
2 changed files with 255 additions and 67 deletions
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34
test/Transforms/JumpThreading/basic.ll
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@ -105,3 +105,37 @@ F2:
ret i32 %B
}
;; This tests that the branch in 'merge' can be cloned up into T1.
define i32 @test5(i1 %cond, i1 %cond2) {
; CHECK: @test5
br i1 %cond, label %T1, label %F1
T1:
; CHECK: T1:
; CHECK-NEXT: %v1 = call i32 @f1()
; CHECK-NEXT: %cond3 = icmp eq i32 %v1, 412
; CHECK-NEXT: br i1 %cond3, label %T2, label %F2
%v1 = call i32 @f1()
%cond3 = icmp eq i32 %v1, 412
br label %Merge
F1:
%v2 = call i32 @f2()
br label %Merge
Merge:
%A = phi i1 [%cond3, %T1], [%cond2, %F1]
%B = phi i32 [%v1, %T1], [%v2, %F1]
br i1 %A, label %T2, label %F2
T2:
call void @f3()
ret i32 %B
F2:
ret i32 %B
}