[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, 4 insertions, 1 deletions

diff --git a/llvm/test/Transforms/ADCE/2003-06-24-BasicFunctionality.ll b/llvm/test/Transforms/ADCE/2003-06-24-BasicFunctionality.ll
index f0de4316436..ac2a30d40b9 100644
--- a/llvm/test/Transforms/ADCE/2003-06-24-BasicFunctionality.ll
+++ b/llvm/test/Transforms/ADCE/2003-06-24-BasicFunctionality.ll
@@ -1,4 +1,5 @@
-; RUN: opt < %s -adce -simplifycfg -S | not grep then:
+; RUN: opt < %s -adce -S | FileCheck %s
+; RUN: opt < %s -adce -adce-remove-loops -S | FileCheck %s
 
 define void @dead_test8(i32* %data.1, i32 %idx.1) {
 entry:
@@ -17,7 +18,9 @@ no_exit:                ; preds = %endif, %no_exit.preheader
         %i.0 = phi i32 [ %inc.1, %endif ], [ 0, %no_exit.preheader ]            ; <i32> [#uses=1]
         %tmp.12 = load i32, i32* %tmp.11             ; <i32> [#uses=1]
         %tmp.14 = sub i32 0, %tmp.12            ; <i32> [#uses=1]
+; CHECK-NOT: %tmp.161
         %tmp.161 = icmp ne i32 %k.1, %tmp.14            ; <i1> [#uses=1]
+; CHECK: br label %then
         br i1 %tmp.161, label %then, label %else
 
 then:           ; preds = %no_exit