[llvm] r370069 - Revert "[CodeGen] Do the Simple Early Return in block-placement pass to optimize the blocks"
Jinsong Ji via llvm-commits
llvm-commits at lists.llvm.org
Tue Aug 27 07:59:08 PDT 2019
Author: jsji
Date: Tue Aug 27 07:59:08 2019
New Revision: 370069
URL: http://llvm.org/viewvc/llvm-project?rev=370069&view=rev
Log:
Revert "[CodeGen] Do the Simple Early Return in block-placement pass to optimize the blocks"
This reverts commit b3d258fc44b588f06eb35f8e4b9a6d1fc859acec.
@skatkov is reporting crash in D63972#1646303
Contacted @ZhangKang, and revert the commit on behalf of him.
Modified:
llvm/trunk/lib/CodeGen/MachineBlockPlacement.cpp
llvm/trunk/test/CodeGen/PowerPC/block-placement.mir
Modified: llvm/trunk/lib/CodeGen/MachineBlockPlacement.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/MachineBlockPlacement.cpp?rev=370069&r1=370068&r2=370069&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/MachineBlockPlacement.cpp (original)
+++ llvm/trunk/lib/CodeGen/MachineBlockPlacement.cpp Tue Aug 27 07:59:08 2019
@@ -2755,7 +2755,6 @@ void MachineBlockPlacement::optimizeBran
// cannot because all branches may not be analyzable.
// E.g., the target may be able to remove an unconditional branch to
// a fallthrough when it occurs after predicated terminators.
- SmallVector<MachineBasicBlock*, 4> EmptyBB;
for (MachineBasicBlock *ChainBB : FunctionChain) {
Cond.clear();
MachineBasicBlock *TBB = nullptr, *FBB = nullptr; // For AnalyzeBranch.
@@ -2775,45 +2774,9 @@ void MachineBlockPlacement::optimizeBran
TII->removeBranch(*ChainBB);
TII->insertBranch(*ChainBB, FBB, TBB, Cond, dl);
ChainBB->updateTerminator();
- } else if (Cond.empty() && TBB && ChainBB != TBB && !TBB->empty() &&
- !TBB->canFallThrough()) {
- // When ChainBB is unconditional branch to the TBB, and TBB has no
- // fallthrough predecessor and fallthrough successor, try to merge
- // ChainBB and TBB. This is legal under the one of following conditions:
- // 1. ChainBB is empty except for an unconditional branch.
- // 2. TBB has only one predecessor.
- MachineFunction::iterator I(TBB);
- if (((TBB == &*F->begin()) || !std::prev(I)->canFallThrough()) &&
- (TailDup.isSimpleBB(ChainBB) || (TBB->pred_size() == 1))) {
- TII->removeBranch(*ChainBB);
- ChainBB->removeSuccessor(TBB);
-
- // Update the CFG.
- while (!TBB->pred_empty()) {
- MachineBasicBlock *Pred = *(TBB->pred_end() - 1);
- Pred->ReplaceUsesOfBlockWith(TBB, ChainBB);
- }
-
- while (!TBB->succ_empty()) {
- MachineBasicBlock *Succ = *(TBB->succ_end() - 1);
- ChainBB->addSuccessor(Succ, MBPI->getEdgeProbability(TBB, Succ));
- TBB->removeSuccessor(Succ);
- }
-
- // Move all the instructions of TBB to ChainBB.
- ChainBB->splice(ChainBB->end(), TBB, TBB->begin(), TBB->end());
- EmptyBB.push_back(TBB);
- }
}
}
}
-
- for (auto BB: EmptyBB) {
- MLI->removeBlock(BB);
- FunctionChain.remove(BB);
- BlockToChain.erase(BB);
- F->erase(BB);
- }
}
void MachineBlockPlacement::alignBlocks() {
@@ -3133,9 +3096,6 @@ bool MachineBlockPlacement::runOnMachine
}
}
- // optimizeBranches() may change the blocks, but we haven't updated the
- // post-dominator tree. Because the post-dominator tree won't be used after
- // this function and this pass don't preserve the post-dominator tree.
optimizeBranches();
alignBlocks();
Modified: llvm/trunk/test/CodeGen/PowerPC/block-placement.mir
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/PowerPC/block-placement.mir?rev=370069&r1=370068&r2=370069&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/PowerPC/block-placement.mir (original)
+++ llvm/trunk/test/CodeGen/PowerPC/block-placement.mir Tue Aug 27 07:59:08 2019
@@ -209,10 +209,14 @@ body: |
BLR8 implicit $lr8, implicit $rm, implicit killed $x3
; CHECK: bb.5.if.else.i:
- ; CHECK-NEXT: renamable $x3 = LI8 1
- ; CHECK-NEXT: BLR8 implicit $lr8, implicit $rm, implicit killed $x3
+ ; CHECK: successors: %bb.11(0x80000000)
+ ; CHECK: B %bb.11
; CHECK: bb.8.while.body.i (align 4):
- ; CHECK: successors: %bb.5(0x04000000), %bb.9(0x7c000000)
- ; CHECK: BCC 76, killed renamable $cr0, %bb.5
+ ; CHECK: successors: %bb.11(0x04000000), %bb.9(0x7c000000)
+ ; CHECK: BCC 76, killed renamable $cr0, %bb.11
+
+ ; CHECK: bb.11:
+ ; CHECK: renamable $x3 = LI8 1
+ ; CHECK-NEXT: BLR8 implicit $lr8, implicit $rm, implicit killed $x3
...
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