Generalize MergeBlockIntoPredecessor. Replace uses of MergeBasicBlockIntoOnlyPred.

Summary:
Two utils methods have essentially the same functionality. This is an attempt to merge them into one.
1. lib/Transforms/Utils/Local.cpp : MergeBasicBlockIntoOnlyPred
2. lib/Transforms/Utils/BasicBlockUtils.cpp : MergeBlockIntoPredecessor

Prior to the patch:
1. MergeBasicBlockIntoOnlyPred
Updates either DomTree or DeferredDominance
Moves all instructions from Pred to BB, deletes Pred
Asserts BB has single predecessor
If address was taken, replace the block address with constant 1 (?)

2. MergeBlockIntoPredecessor
Updates DomTree, LoopInfo and MemoryDependenceResults
Moves all instruction from BB to Pred, deletes BB
Returns if doesn't have a single predecessor
Returns if BB's address was taken

After the patch:
Method 2. MergeBlockIntoPredecessor is attempting to become the new default:
Updates DomTree or DeferredDominance, and LoopInfo and MemoryDependenceResults
Moves all instruction from BB to Pred, deletes BB
Returns if doesn't have a single predecessor
Returns if BB's address was taken

Uses of MergeBasicBlockIntoOnlyPred that need to be replaced:

1. lib/Transforms/Scalar/LoopSimplifyCFG.cpp
Updated in this patch. No challenges.

2. lib/CodeGen/CodeGenPrepare.cpp
Updated in this patch.
  i. eliminateFallThrough is straightforward, but I added using a temporary array to avoid the iterator invalidation.
  ii. eliminateMostlyEmptyBlock(s) methods also now use a temporary array for blocks
Some interesting aspects:
  - Since Pred is not deleted (BB is), the entry block does not need updating.
  - The entry block was being updated with the deleted block in eliminateMostlyEmptyBlock. Added assert to make obvious that BB=SinglePred.
  - isMergingEmptyBlockProfitable assumes BB is the one to be deleted.
  - eliminateMostlyEmptyBlock(BB) does not delete BB on one path, it deletes its unique predecessor instead.
  - adding some test owner as subscribers for the interesting tests modified:
    test/CodeGen/X86/avx-cmp.ll
    test/CodeGen/AMDGPU/nested-loop-conditions.ll
    test/CodeGen/AMDGPU/si-annotate-cf.ll
    test/CodeGen/X86/hoist-spill.ll
    test/CodeGen/X86/2006-11-17-IllegalMove.ll

3. lib/Transforms/Scalar/JumpThreading.cpp
Not covered in this patch. It is the only use case using the DeferredDominance.
I would defer to Brian Rzycki to make this replacement.

Reviewers: chandlerc, spatel, davide, brzycki, bkramer, javed.absar

Subscribers: qcolombet, sanjoy, nemanjai, nhaehnle, jlebar, tpr, kbarton, RKSimon, wmi, arsenm, llvm-commits

Differential Revision: https://reviews.llvm.org/D48202

llvm-svn: 335183

4 files changed, 4 insertions, 4 deletions

diff --git a/llvm/test/CodeGen/PowerPC/memCmpUsedInZeroEqualityComparison.ll b/llvm/test/CodeGen/PowerPC/memCmpUsedInZeroEqualityComparison.ll
index 3bfc0de1b87..fd9121a59a4 100644
--- a/llvm/test/CodeGen/PowerPC/memCmpUsedInZeroEqualityComparison.ll
+++ b/llvm/test/CodeGen/PowerPC/memCmpUsedInZeroEqualityComparison.ll
@@ -160,7 +160,7 @@ define signext i32 @zeroEqualityTest05() {
 ; Validate with memcmp()?:
 define signext i32 @equalityFoldTwoConstants() {
 ; CHECK-LABEL: equalityFoldTwoConstants:
-; CHECK:       # %bb.0: # %endblock
+; CHECK:       # %bb.0: # %loadbb
 ; CHECK-NEXT:    li 3, 1
 ; CHECK-NEXT:    blr
   %call = tail call signext i32 @memcmp(i8* bitcast ([15 x i32]* @zeroEqualityTest04.buffer1 to i8*), i8* bitcast ([15 x i32]* @zeroEqualityTest04.buffer2 to i8*), i64 16)
diff --git a/llvm/test/CodeGen/PowerPC/memcmp-mergeexpand.ll b/llvm/test/CodeGen/PowerPC/memcmp-mergeexpand.ll
index 83b1cd505db..c1e81074c86 100644
--- a/llvm/test/CodeGen/PowerPC/memcmp-mergeexpand.ll
+++ b/llvm/test/CodeGen/PowerPC/memcmp-mergeexpand.ll
@@ -7,7 +7,7 @@
 
 define zeroext i1 @opeq1(
 ; PPC64LE-LABEL: opeq1:
-; PPC64LE:       # %bb.0: # %opeq1.exit
+; PPC64LE:       # %bb.0: # %entry
 ; PPC64LE-NEXT:    ld 3, 0(3)
 ; PPC64LE-NEXT:    ld 4, 0(4)
 ; PPC64LE-NEXT:    xor 3, 3, 4
diff --git a/llvm/test/CodeGen/PowerPC/ppc-shrink-wrapping.ll b/llvm/test/CodeGen/PowerPC/ppc-shrink-wrapping.ll
index 6886b4efa85..621bda04159 100644
--- a/llvm/test/CodeGen/PowerPC/ppc-shrink-wrapping.ll
+++ b/llvm/test/CodeGen/PowerPC/ppc-shrink-wrapping.ll
@@ -169,7 +169,7 @@ declare i32 @something(...)
 ; CHECK-NEXT: bne 0, .[[LOOP]]
 ;
 ; Next BB
-; CHECK: %for.end
+; CHECK: %for.exit
 ; CHECK: mtlr {{[0-9]+}}
 ; CHECK-NEXT: blr
 define i32 @freqSaveAndRestoreOutsideLoop2(i32 %cond) {
diff --git a/llvm/test/CodeGen/PowerPC/simplifyConstCmpToISEL.ll b/llvm/test/CodeGen/PowerPC/simplifyConstCmpToISEL.ll
index 3988d9c8d5a..bf5754dc914 100644
--- a/llvm/test/CodeGen/PowerPC/simplifyConstCmpToISEL.ll
+++ b/llvm/test/CodeGen/PowerPC/simplifyConstCmpToISEL.ll
@@ -3,7 +3,7 @@
 ; RUN:   -ppc-convert-rr-to-ri -verify-machineinstrs | FileCheck %s
 define void @test(i32 zeroext %parts) {
 ; CHECK-LABEL: test:
-; CHECK:       # %bb.0: # %cond.end.i
+; CHECK:       # %bb.0: # %entry
 ; CHECK-NEXT:    cmplwi 0, 3, 1
 ; CHECK-NEXT:    bnelr+ 0
 ; CHECK-NEXT:  # %bb.1: # %test2.exit.us.unr-lcssa