maxjhandsome
/
llvm-project
forked from OSchip/llvm-project
1
0
Fork 0
Code Issues Pull Requests Packages Releases Wiki Activity

Return "[LoopSimplifyCFG] Delete dead in-loop blocks" 

The underlying bug that caused the revert should be fixed by rL348567.

Differential Revision: https://reviews.llvm.org/D54023

llvm-svn: 350045
This commit is contained in:
Max Kazantsev 2018-12-24 06:06:17 +00:00
parent 7e12875c89
commit 347c583772
2 changed files with 58 additions and 114 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

42
llvm/lib/Transforms/Scalar/LoopSimplifyCFG.cpp
View File

@ -46,6 +46,8 @@ static cl::opt<bool> EnableTermFolding("enable-loop-simplifycfg-term-folding",
STATISTIC(NumTerminatorsFolded,
"Number of terminators folded to unconditional branches");
STATISTIC(NumLoopBlocksDeleted,
"Number of loop blocks deleted");
/// If \p BB is a switch or a conditional branch, but only one of its successors
/// can be reached from this block in runtime, return this successor. Otherwise,
@ -269,6 +271,27 @@ private:
"All blocks that stay in loop should be live!");
}
/// Delete loop blocks that have become unreachable after folding. Make all
/// relevant updates to DT and LI.
void deleteDeadLoopBlocks() {
DomTreeUpdater DTU(DT, DomTreeUpdater::UpdateStrategy::Eager);
if (MSSAU)
MSSAU->removeBlocks(DeadLoopBlocks);
for (auto *BB : DeadLoopBlocks) {
assert(BB != L.getHeader() &&
"Header of the current loop cannot be dead!");
LLVM_DEBUG(dbgs() << "Deleting dead loop block " << BB->getName()
<< "\n");
if (LI.isLoopHeader(BB)) {
assert(LI.getLoopFor(BB) != &L && "Attempt to remove current loop!");
LI.erase(LI.getLoopFor(BB));
}
LI.removeBlock(BB);
DeleteDeadBlock(BB, &DTU);
++NumLoopBlocksDeleted;
}
}
/// Constant-fold terminators of blocks acculumated in FoldCandidates into the
/// unconditional branches.
void foldTerminators() {
@ -358,15 +381,6 @@ public:
return false;
}
// TODO: Support deletion of dead loop blocks.
if (!DeadLoopBlocks.empty()) {
LLVM_DEBUG(dbgs() << "Give up constant terminator folding in loop "
<< L.getHeader()->getName()
<< ": we don't currently"
" support deletion of dead in-loop blocks.\n");
return false;
}
// TODO: Support dead loop exits.
if (!DeadExitBlocks.empty()) {
LLVM_DEBUG(dbgs() << "Give up constant terminator folding in loop "
@ -377,7 +391,8 @@ public:
// TODO: Support blocks that are not dead, but also not in loop after the
// folding.
if (BlocksInLoopAfterFolding.size() != L.getNumBlocks()) {
if (BlocksInLoopAfterFolding.size() + DeadLoopBlocks.size() !=
L.getNumBlocks()) {
LLVM_DEBUG(
dbgs() << "Give up constant terminator folding in loop "
<< L.getHeader()->getName()
@ -397,6 +412,13 @@ public:
// Make the actual transforms.
foldTerminators();
if (!DeadLoopBlocks.empty()) {
LLVM_DEBUG(dbgs() << "Deleting " << DeadLoopBlocks.size()
<< " dead blocks in loop " << L.getHeader()->getName()
<< "\n");
deleteDeadLoopBlocks();
}
#ifndef NDEBUG
// Make sure that we have preserved all data structures after the transform.
DT.verify();

130
llvm/test/Transforms/LoopSimplifyCFG/constant-fold-branch.ll
View File

@ -88,18 +88,12 @@ define i32 @dead_block_test_branch_loop(i32 %end) {
; CHECK-NEXT: preheader:
; CHECK-NEXT: br label [[HEADER:%.*]]
; CHECK: header:
; CHECK-NEXT: [[I:%.*]] = phi i32 [ 0, [[PREHEADER:%.*]] ], [ [[I_INC:%.*]], [[BACKEDGE:%.*]] ]
; CHECK-NEXT: br i1 true, label [[BACKEDGE]], label [[DEAD:%.*]]
; CHECK: dead:
; CHECK-NEXT: [[I_2:%.*]] = add i32 [[I]], 1
; CHECK-NEXT: br label [[BACKEDGE]]
; CHECK: backedge:
; CHECK-NEXT: [[I_1:%.*]] = phi i32 [ [[I]], [[HEADER]] ], [ [[I_2]], [[DEAD]] ]
; CHECK-NEXT: [[I_INC]] = add i32 [[I_1]], 1
; CHECK-NEXT: [[I:%.*]] = phi i32 [ 0, [[PREHEADER:%.*]] ], [ [[I_INC:%.*]], [[HEADER]] ]
; CHECK-NEXT: [[I_INC]] = add i32 [[I]], 1
; CHECK-NEXT: [[CMP:%.*]] = icmp slt i32 [[I_INC]], [[END:%.*]]
; CHECK-NEXT: br i1 [[CMP]], label [[HEADER]], label [[EXIT:%.*]]
; CHECK: exit:
; CHECK-NEXT: [[I_INC_LCSSA:%.*]] = phi i32 [ [[I_INC]], [[BACKEDGE]] ]
; CHECK-NEXT: [[I_INC_LCSSA:%.*]] = phi i32 [ [[I_INC]], [[HEADER]] ]
; CHECK-NEXT: ret i32 [[I_INC_LCSSA]]
;
preheader:
@ -129,22 +123,12 @@ define i32 @dead_block_test_switch_loop(i32 %end) {
; CHECK-NEXT: preheader:
; CHECK-NEXT: br label [[HEADER:%.*]]
; CHECK: header:
; CHECK-NEXT: [[I:%.*]] = phi i32 [ 0, [[PREHEADER:%.*]] ], [ [[I_INC:%.*]], [[BACKEDGE:%.*]] ]
; CHECK-NEXT: switch i32 1, label [[DEAD:%.*]] [
; CHECK-NEXT: i32 0, label [[DEAD]]
; CHECK-NEXT: i32 1, label [[BACKEDGE]]
; CHECK-NEXT: i32 2, label [[DEAD]]
; CHECK-NEXT: ]
; CHECK: dead:
; CHECK-NEXT: [[I_2:%.*]] = add i32 [[I]], 1
; CHECK-NEXT: br label [[BACKEDGE]]
; CHECK: backedge:
; CHECK-NEXT: [[I_1:%.*]] = phi i32 [ [[I]], [[HEADER]] ], [ [[I_2]], [[DEAD]] ]
; CHECK-NEXT: [[I_INC]] = add i32 [[I_1]], 1
; CHECK-NEXT: [[I:%.*]] = phi i32 [ 0, [[PREHEADER:%.*]] ], [ [[I_INC:%.*]], [[HEADER]] ]
; CHECK-NEXT: [[I_INC]] = add i32 [[I]], 1
; CHECK-NEXT: [[CMP:%.*]] = icmp slt i32 [[I_INC]], [[END:%.*]]
; CHECK-NEXT: br i1 [[CMP]], label [[HEADER]], label [[EXIT:%.*]]
; CHECK: exit:
; CHECK-NEXT: [[I_INC_LCSSA:%.*]] = phi i32 [ [[I_INC]], [[BACKEDGE]] ]
; CHECK-NEXT: [[I_INC_LCSSA:%.*]] = phi i32 [ [[I_INC]], [[HEADER]] ]
; CHECK-NEXT: ret i32 [[I_INC_LCSSA]]
;
preheader:
@ -175,18 +159,12 @@ define i32 @dead_block_propogate_test_branch_loop(i32 %end) {
; CHECK-NEXT: preheader:
; CHECK-NEXT: br label [[HEADER:%.*]]
; CHECK: header:
; CHECK-NEXT: [[I:%.*]] = phi i32 [ 0, [[PREHEADER:%.*]] ], [ [[I_INC:%.*]], [[BACKEDGE:%.*]] ]
; CHECK-NEXT: br i1 true, label [[BACKEDGE]], label [[DEAD:%.*]]
; CHECK: dead:
; CHECK-NEXT: [[I_2:%.*]] = add i32 [[I]], 1
; CHECK-NEXT: br label [[BACKEDGE]]
; CHECK: backedge:
; CHECK-NEXT: [[I_1:%.*]] = phi i32 [ [[I]], [[HEADER]] ], [ [[I_2]], [[DEAD]] ]
; CHECK-NEXT: [[I_INC]] = add i32 [[I_1]], 1
; CHECK-NEXT: [[I:%.*]] = phi i32 [ 0, [[PREHEADER:%.*]] ], [ [[I_INC:%.*]], [[HEADER]] ]
; CHECK-NEXT: [[I_INC]] = add i32 [[I]], 1
; CHECK-NEXT: [[CMP:%.*]] = icmp slt i32 [[I_INC]], [[END:%.*]]
; CHECK-NEXT: br i1 [[CMP]], label [[HEADER]], label [[EXIT:%.*]]
; CHECK: exit:
; CHECK-NEXT: [[I_INC_LCSSA:%.*]] = phi i32 [ [[I_INC]], [[BACKEDGE]] ]
; CHECK-NEXT: [[I_INC_LCSSA:%.*]] = phi i32 [ [[I_INC]], [[HEADER]] ]
; CHECK-NEXT: ret i32 [[I_INC_LCSSA]]
;
preheader:
@ -219,22 +197,12 @@ define i32 @dead_block_propogate_test_switch_loop(i32 %end) {
; CHECK-NEXT: preheader:
; CHECK-NEXT: br label [[HEADER:%.*]]
; CHECK: header:
; CHECK-NEXT: [[I:%.*]] = phi i32 [ 0, [[PREHEADER:%.*]] ], [ [[I_INC:%.*]], [[BACKEDGE:%.*]] ]
; CHECK-NEXT: switch i32 1, label [[DEAD:%.*]] [
; CHECK-NEXT: i32 0, label [[DEAD]]
; CHECK-NEXT: i32 1, label [[BACKEDGE]]
; CHECK-NEXT: i32 2, label [[DEAD]]
; CHECK-NEXT: ]
; CHECK: dead:
; CHECK-NEXT: [[I_2:%.*]] = add i32 [[I]], 1
; CHECK-NEXT: br label [[BACKEDGE]]
; CHECK: backedge:
; CHECK-NEXT: [[I_1:%.*]] = phi i32 [ [[I]], [[HEADER]] ], [ [[I_2]], [[DEAD]] ]
; CHECK-NEXT: [[I_INC]] = add i32 [[I_1]], 1
; CHECK-NEXT: [[I:%.*]] = phi i32 [ 0, [[PREHEADER:%.*]] ], [ [[I_INC:%.*]], [[HEADER]] ]
; CHECK-NEXT: [[I_INC]] = add i32 [[I]], 1
; CHECK-NEXT: [[CMP:%.*]] = icmp slt i32 [[I_INC]], [[END:%.*]]
; CHECK-NEXT: br i1 [[CMP]], label [[HEADER]], label [[EXIT:%.*]]
; CHECK: exit:
; CHECK-NEXT: [[I_INC_LCSSA:%.*]] = phi i32 [ [[I_INC]], [[BACKEDGE]] ]
; CHECK-NEXT: [[I_INC_LCSSA:%.*]] = phi i32 [ [[I_INC]], [[HEADER]] ]
; CHECK-NEXT: ret i32 [[I_INC_LCSSA]]
;
preheader:
@ -463,32 +431,19 @@ define i32 @dead_sub_loop_test_branch_loop(i32 %end) {
; CHECK-NEXT: preheader:
; CHECK-NEXT: br label [[HEADER:%.*]]
; CHECK: header:
; CHECK-NEXT: [[I:%.*]] = phi i32 [ 0, [[PREHEADER:%.*]] ], [ [[I_INC:%.*]], [[BACKEDGE:%.*]] ]
; CHECK-NEXT: br i1 true, label [[LIVE_PREHEADER:%.*]], label [[DEAD_PREHEADER:%.*]]
; CHECK: live_preheader:
; CHECK-NEXT: [[I:%.*]] = phi i32 [ 0, [[PREHEADER:%.*]] ], [ [[I_INC:%.*]], [[EXIT_A:%.*]] ]
; CHECK-NEXT: br label [[LIVE_LOOP:%.*]]
; CHECK: live_loop:
; CHECK-NEXT: [[A:%.*]] = phi i32 [ 0, [[LIVE_PREHEADER]] ], [ [[A_INC:%.*]], [[LIVE_LOOP]] ]
; CHECK-NEXT: [[A:%.*]] = phi i32 [ 0, [[HEADER]] ], [ [[A_INC:%.*]], [[LIVE_LOOP]] ]
; CHECK-NEXT: [[A_INC]] = add i32 [[A]], 1
; CHECK-NEXT: [[CMP_A:%.*]] = icmp slt i32 [[A_INC]], [[END:%.*]]
; CHECK-NEXT: br i1 [[CMP_A]], label [[LIVE_LOOP]], label [[EXIT_A:%.*]]
; CHECK-NEXT: br i1 [[CMP_A]], label [[LIVE_LOOP]], label [[EXIT_A]]
; CHECK: exit.a:
; CHECK-NEXT: br label [[BACKEDGE]]
; CHECK: dead_preheader:
; CHECK-NEXT: br label [[DEAD_LOOP:%.*]]
; CHECK: dead_loop:
; CHECK-NEXT: [[B:%.*]] = phi i32 [ 0, [[DEAD_PREHEADER]] ], [ [[B_INC:%.*]], [[DEAD_LOOP]] ]
; CHECK-NEXT: [[B_INC]] = add i32 [[B]], 1
; CHECK-NEXT: [[CMP_B:%.*]] = icmp slt i32 [[B_INC]], [[END]]
; CHECK-NEXT: br i1 [[CMP_B]], label [[DEAD_LOOP]], label [[EXIT_B:%.*]]
; CHECK: exit.b:
; CHECK-NEXT: br label [[BACKEDGE]]
; CHECK: backedge:
; CHECK-NEXT: [[I_INC]] = add i32 [[I]], 1
; CHECK-NEXT: [[CMP:%.*]] = icmp slt i32 [[I_INC]], [[END]]
; CHECK-NEXT: br i1 [[CMP]], label [[HEADER]], label [[EXIT:%.*]]
; CHECK: exit:
; CHECK-NEXT: [[I_INC_LCSSA:%.*]] = phi i32 [ [[I_INC]], [[BACKEDGE]] ]
; CHECK-NEXT: [[I_INC_LCSSA:%.*]] = phi i32 [ [[I_INC]], [[EXIT_A]] ]
; CHECK-NEXT: ret i32 [[I_INC_LCSSA]]
;
preheader:
@ -536,36 +491,19 @@ define i32 @dead_sub_loop_test_switch_loop(i32 %end) {
; CHECK-NEXT: preheader:
; CHECK-NEXT: br label [[HEADER:%.*]]
; CHECK: header:
; CHECK-NEXT: [[I:%.*]] = phi i32 [ 0, [[PREHEADER:%.*]] ], [ [[I_INC:%.*]], [[BACKEDGE:%.*]] ]
; CHECK-NEXT: switch i32 1, label [[DEAD_PREHEADER:%.*]] [
; CHECK-NEXT: i32 0, label [[DEAD_PREHEADER]]
; CHECK-NEXT: i32 1, label [[LIVE_PREHEADER:%.*]]
; CHECK-NEXT: i32 2, label [[DEAD_PREHEADER]]
; CHECK-NEXT: ]
; CHECK: live_preheader:
; CHECK-NEXT: [[I:%.*]] = phi i32 [ 0, [[PREHEADER:%.*]] ], [ [[I_INC:%.*]], [[EXIT_A:%.*]] ]
; CHECK-NEXT: br label [[LIVE_LOOP:%.*]]
; CHECK: live_loop:
; CHECK-NEXT: [[A:%.*]] = phi i32 [ 0, [[LIVE_PREHEADER]] ], [ [[A_INC:%.*]], [[LIVE_LOOP]] ]
; CHECK-NEXT: [[A:%.*]] = phi i32 [ 0, [[HEADER]] ], [ [[A_INC:%.*]], [[LIVE_LOOP]] ]
; CHECK-NEXT: [[A_INC]] = add i32 [[A]], 1
; CHECK-NEXT: [[CMP_A:%.*]] = icmp slt i32 [[A_INC]], [[END:%.*]]
; CHECK-NEXT: br i1 [[CMP_A]], label [[LIVE_LOOP]], label [[EXIT_A:%.*]]
; CHECK-NEXT: br i1 [[CMP_A]], label [[LIVE_LOOP]], label [[EXIT_A]]
; CHECK: exit.a:
; CHECK-NEXT: br label [[BACKEDGE]]
; CHECK: dead_preheader:
; CHECK-NEXT: br label [[DEAD_LOOP:%.*]]
; CHECK: dead_loop:
; CHECK-NEXT: [[B:%.*]] = phi i32 [ 0, [[DEAD_PREHEADER]] ], [ [[B_INC:%.*]], [[DEAD_LOOP]] ]
; CHECK-NEXT: [[B_INC]] = add i32 [[B]], 1
; CHECK-NEXT: [[CMP_B:%.*]] = icmp slt i32 [[B_INC]], [[END]]
; CHECK-NEXT: br i1 [[CMP_B]], label [[DEAD_LOOP]], label [[EXIT_B:%.*]]
; CHECK: exit.b:
; CHECK-NEXT: br label [[BACKEDGE]]
; CHECK: backedge:
; CHECK-NEXT: [[I_INC]] = add i32 [[I]], 1
; CHECK-NEXT: [[CMP:%.*]] = icmp slt i32 [[I_INC]], [[END]]
; CHECK-NEXT: br i1 [[CMP]], label [[HEADER]], label [[EXIT:%.*]]
; CHECK: exit:
; CHECK-NEXT: [[I_INC_LCSSA:%.*]] = phi i32 [ [[I_INC]], [[BACKEDGE]] ]
; CHECK-NEXT: [[I_INC_LCSSA:%.*]] = phi i32 [ [[I_INC]], [[EXIT_A]] ]
; CHECK-NEXT: ret i32 [[I_INC_LCSSA]]
;
preheader:
@ -898,18 +836,12 @@ define i32 @partial_sub_loop_test_branch_loop(i32 %end) {
; CHECK-NEXT: [[J:%.*]] = phi i32 [ 0, [[ENTRY:%.*]] ], [ [[J_INC:%.*]], [[OUTER_BACKEDGE:%.*]] ]
; CHECK-NEXT: br label [[HEADER:%.*]]
; CHECK: header:
; CHECK-NEXT: [[I:%.*]] = phi i32 [ 0, [[OUTER_HEADER]] ], [ [[I_INC:%.*]], [[BACKEDGE:%.*]] ]
; CHECK-NEXT: br i1 true, label [[BACKEDGE]], label [[DEAD:%.*]]
; CHECK: dead:
; CHECK-NEXT: [[I_2:%.*]] = add i32 [[I]], 1
; CHECK-NEXT: br label [[BACKEDGE]]
; CHECK: backedge:
; CHECK-NEXT: [[I_1:%.*]] = phi i32 [ [[I]], [[HEADER]] ], [ [[I_2]], [[DEAD]] ]
; CHECK-NEXT: [[I_INC]] = add i32 [[I_1]], 1
; CHECK-NEXT: [[I:%.*]] = phi i32 [ 0, [[OUTER_HEADER]] ], [ [[I_INC:%.*]], [[HEADER]] ]
; CHECK-NEXT: [[I_INC]] = add i32 [[I]], 1
; CHECK-NEXT: [[CMP:%.*]] = icmp slt i32 [[I_INC]], [[END:%.*]]
; CHECK-NEXT: br i1 [[CMP]], label [[HEADER]], label [[OUTER_BACKEDGE]]
; CHECK: outer_backedge:
; CHECK-NEXT: [[I_INC_LCSSA:%.*]] = phi i32 [ [[I_INC]], [[BACKEDGE]] ]
; CHECK-NEXT: [[I_INC_LCSSA:%.*]] = phi i32 [ [[I_INC]], [[HEADER]] ]
; CHECK-NEXT: [[J_INC]] = add i32 [[J]], 1
; CHECK-NEXT: [[CMP_J:%.*]] = icmp slt i32 [[J_INC]], [[END]]
; CHECK-NEXT: br i1 [[CMP_J]], label [[OUTER_HEADER]], label [[EXIT:%.*]]
@ -958,22 +890,12 @@ define i32 @partial_sub_loop_test_switch_loop(i32 %end) {
; CHECK-NEXT: [[J:%.*]] = phi i32 [ 0, [[ENTRY:%.*]] ], [ [[J_INC:%.*]], [[OUTER_BACKEDGE:%.*]] ]
; CHECK-NEXT: br label [[HEADER:%.*]]
; CHECK: header:
; CHECK-NEXT: [[I:%.*]] = phi i32 [ 0, [[OUTER_HEADER]] ], [ [[I_INC:%.*]], [[BACKEDGE:%.*]] ]
; CHECK-NEXT: switch i32 1, label [[DEAD:%.*]] [
; CHECK-NEXT: i32 0, label [[DEAD]]
; CHECK-NEXT: i32 1, label [[BACKEDGE]]
; CHECK-NEXT: i32 2, label [[DEAD]]
; CHECK-NEXT: ]
; CHECK: dead:
; CHECK-NEXT: [[I_2:%.*]] = add i32 [[I]], 1
; CHECK-NEXT: br label [[BACKEDGE]]
; CHECK: backedge:
; CHECK-NEXT: [[I_1:%.*]] = phi i32 [ [[I]], [[HEADER]] ], [ [[I_2]], [[DEAD]] ]
; CHECK-NEXT: [[I_INC]] = add i32 [[I_1]], 1
; CHECK-NEXT: [[I:%.*]] = phi i32 [ 0, [[OUTER_HEADER]] ], [ [[I_INC:%.*]], [[HEADER]] ]
; CHECK-NEXT: [[I_INC]] = add i32 [[I]], 1
; CHECK-NEXT: [[CMP:%.*]] = icmp slt i32 [[I_INC]], [[END:%.*]]
; CHECK-NEXT: br i1 [[CMP]], label [[HEADER]], label [[OUTER_BACKEDGE]]
; CHECK: outer_backedge:
; CHECK-NEXT: [[I_INC_LCSSA:%.*]] = phi i32 [ [[I_INC]], [[BACKEDGE]] ]
; CHECK-NEXT: [[I_INC_LCSSA:%.*]] = phi i32 [ [[I_INC]], [[HEADER]] ]
; CHECK-NEXT: [[J_INC]] = add i32 [[J]], 1
; CHECK-NEXT: [[CMP_J:%.*]] = icmp slt i32 [[J_INC]], [[END]]
; CHECK-NEXT: br i1 [[CMP_J]], label [[OUTER_HEADER]], label [[EXIT:%.*]]