[ADCE] Add code to remove dead branches

Summary:
This is last in of a series of patches to evolve ADCE.cpp to support
removing of unnecessary control flow.

This patch adds the code to update the control and data flow graphs
to remove the dead control flow.

Also update unit tests to test the capability to remove dead,
may-be-infinite loop which is enabled by the switch
-adce-remove-loops.

Previous patches:

D23824 [ADCE] Add handling of PHI nodes when removing control flow
D23559 [ADCE] Add control dependence computation
D23225 [ADCE] Modify data structures to support removing control flow
D23065 [ADCE] Refactor anticipating new functionality (NFC)
D23102 [ADCE] Refactoring for new functionality (NFC)

Reviewers: dberlin, majnemer, nadav, mehdi_amini

Subscribers: llvm-commits, david2050, freik, twoh

Differential Revision: https://reviews.llvm.org/D24918

llvm-svn: 289548

1 files changed, 3 insertions, 1 deletions

diff --git a/llvm/test/Transforms/ADCE/2003-04-25-PHIPostDominateProblem.ll b/llvm/test/Transforms/ADCE/2003-04-25-PHIPostDominateProblem.ll
index d30df19fc7c..37adba599cd 100644
--- a/llvm/test/Transforms/ADCE/2003-04-25-PHIPostDominateProblem.ll
+++ b/llvm/test/Transforms/ADCE/2003-04-25-PHIPostDominateProblem.ll
@@ -2,7 +2,8 @@
 ; entries for it's postdominator.  But I think this can only happen when the 
 ; PHI node is dead, so we just avoid patching up dead PHI nodes.
 
-; RUN: opt < %s -adce
+; RUN: opt < %s -adce                    -S | FileCheck %s
+; RUN: opt < %s -adce -adce-remove-loops -S | FileCheck %s
 
 target datalayout = "e-p:32:32"
 
@@ -15,6 +16,7 @@ loopentry:              ; preds = %endif, %entry
         br i1 false, label %no_exit, label %return
 
 no_exit:                ; preds = %loopentry
+; CHECK: br label %then
         br i1 false, label %then, label %else
 
 then:           ; preds = %no_exit