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make jump threading recursively simplify expressions instead of doing it

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just one level deep.  On the testcase we go from getting this:

F1:                                               ; preds = %T2
  %F = and i1 true, %cond                         ; <i1> [#uses=1]
  br i1 %F, label %X, label %Y

to a fully threaded:

F1:                                               ; preds = %T2
  br label %Y


This changes gets us to the point where we're forming (too many) switch 
instructions on doug's strswitch testcase.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86646 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner
2009-11-10 01:57:31 +00:00
parent 9f3ce36d7e
commit fddcf47a24
2 changed files with 74 additions and 20 deletions
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32
test/Transforms/JumpThreading/basic.ll
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@@ -203,3 +203,35 @@ F2:
; CHECK-NEXT: phi i32
}
declare i1 @test8a()
define i32 @test8b(i1 %cond, i1 %cond2) {
; CHECK: @test8b
T0:
%A = call i1 @test8a()
br i1 %A, label %T1, label %F1
T1:
%B = call i1 @test8a()
br i1 %B, label %T2, label %F1
T2:
%C = call i1 @test8a()
br i1 %cond, label %T3, label %F1
T3:
ret i32 0
F1:
; TODO: F1 uncond branch block should be removed, T2 should jump directly to Y.
; CHECK: F1:
; CHECK-NEXT br label %Y
%D = phi i32 [0, %T0], [0, %T1], [1, %T2]
%E = icmp eq i32 %D, 1
%F = and i1 %E, %cond
br i1 %F, label %X, label %Y
X:
call i1 @test8a()
ret i32 1
Y:
ret i32 2
}