[llvm] r278484 - Revert "[BranchFolding] Restrict tail merging loop blocks after MBP"
Haicheng Wu via llvm-commits
llvm-commits at lists.llvm.org
Fri Aug 12 01:40:24 PDT 2016
Author: haicheng
Date: Fri Aug 12 03:40:24 2016
New Revision: 278484
URL: http://llvm.org/viewvc/llvm-project?rev=278484&view=rev
Log:
Revert "[BranchFolding] Restrict tail merging loop blocks after MBP"
This reverts commit r278463 because it hits the bot.
Removed:
llvm/trunk/test/CodeGen/X86/tail-merge-after-mbp.ll
Modified:
llvm/trunk/lib/CodeGen/BranchFolding.cpp
llvm/trunk/test/CodeGen/ARM/arm-and-tst-peephole.ll
Modified: llvm/trunk/lib/CodeGen/BranchFolding.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/BranchFolding.cpp?rev=278484&r1=278483&r2=278484&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/BranchFolding.cpp (original)
+++ llvm/trunk/lib/CodeGen/BranchFolding.cpp Fri Aug 12 03:40:24 2016
@@ -1005,24 +1005,6 @@ bool BranchFolder::TailMergeBlocks(Machi
MachineBasicBlock *IBB = &*I;
MachineBasicBlock *PredBB = &*std::prev(I);
MergePotentials.clear();
- MachineLoop *ML;
-
- // Bail if merging after placement and IBB is the loop header because
- // -- If merging predecessors that belong to the same loop as IBB, the
- // common tail of merged predecessors may become the loop top if block
- // placement is called again and the predecessors may branch to this common
- // tail and require more branches. This can be relaxed if
- // MachineBlockPlacement::findBestLoopTop is more flexible.
- // --If merging predecessors that do not belong to the same loop as IBB, the
- // loop info of IBB's loop and the other loops may be affected. Calling the
- // block placement again may make big change to the layout and eliminate the
- // reason to do tail merging here.
- if (AfterBlockPlacement && MLI) {
- ML = MLI->getLoopFor(IBB);
- if (ML && IBB == ML->getHeader())
- continue;
- }
-
for (MachineBasicBlock *PBB : I->predecessors()) {
if (MergePotentials.size() == TailMergeThreshold)
break;
@@ -1042,12 +1024,16 @@ bool BranchFolder::TailMergeBlocks(Machi
if (PBB->hasEHPadSuccessor())
continue;
- // After block placement, only consider predecessors that belong to the
- // same loop as IBB. The reason is the same as above when skipping loop
- // header.
+ // Bail out if the loop header (IBB) is not the top of the loop chain
+ // after the block placement. Otherwise, the common tail of IBB's
+ // predecessors may become the loop top if block placement is called again
+ // and the predecessors may branch to this common tail.
+ // FIXME: Relaxed this check if the algorithm of finding loop top is
+ // changed in MBP.
if (AfterBlockPlacement && MLI)
- if (ML != MLI->getLoopFor(PBB))
- continue;
+ if (MachineLoop *ML = MLI->getLoopFor(IBB))
+ if (IBB == ML->getHeader() && ML == MLI->getLoopFor(PBB))
+ continue;
MachineBasicBlock *TBB = nullptr, *FBB = nullptr;
SmallVector<MachineOperand, 4> Cond;
Modified: llvm/trunk/test/CodeGen/ARM/arm-and-tst-peephole.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/ARM/arm-and-tst-peephole.ll?rev=278484&r1=278483&r2=278484&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/ARM/arm-and-tst-peephole.ll (original)
+++ llvm/trunk/test/CodeGen/ARM/arm-and-tst-peephole.ll Fri Aug 12 03:40:24 2016
@@ -49,7 +49,7 @@ tailrecurse.switch:
; V8-NEXT: beq
; V8-NEXT: %tailrecurse.switch
; V8: cmp
-; V8-NEXT: bne
+; V8-NEXT: beq
; V8-NEXT: b
; The trailing space in the last line checks that the branch is unconditional
switch i32 %and, label %sw.epilog [
Removed: llvm/trunk/test/CodeGen/X86/tail-merge-after-mbp.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/tail-merge-after-mbp.ll?rev=278483&view=auto
==============================================================================
--- llvm/trunk/test/CodeGen/X86/tail-merge-after-mbp.ll (original)
+++ llvm/trunk/test/CodeGen/X86/tail-merge-after-mbp.ll (removed)
@@ -1,92 +0,0 @@
-; RUN: llc -o - %s | FileCheck %s
-
-%0 = type { %1, %3* }
-%1 = type { %2* }
-%2 = type { %2*, i8* }
-%3 = type { i32, i32 (i32, i32)* }
-
-
-declare i32 @Up(...)
-declare i32 @f(i32, i32)
-
-; check loop block BB#10 is not merged with LBB0_12
-; check loop block LBB0_9 is not merged with BB#11, BB#13
-define i32 @foo(%0* nocapture readonly, i32, i1 %c, i8* %p1, %2** %p2) {
-; CHECK-LABEL: foo:
-; CHECK: LBB0_9:
-; CHECK-NEXT: movq (%r14), %rax
-; CHECK-NEXT: testq %rax, %rax
-; CHECK-NEXT: je
-; CHECK-NEXT:# BB#10:
-; CHECK-NEXT: cmpq $0, 8(%rax)
-; CHECK-NEXT: jne
-; CHECK-NEXT:# BB#11:
-; CHECK-NEXT: movq (%r14), %rax
-; CHECK-NEXT: testq %rax, %rax
-; CHECK-NEXT: je
-; CHECK-NEXT:LBB0_12:
-; CHECK-NEXT: cmpq $0, 8(%rax)
-; CHECK-NEXT: jne
-; CHECK-NEXT:# BB#13:
-; CHECK-NEXT: movq (%r14), %rax
-; CHECK-NEXT: testq %rax, %rax
-; CHECK-NEXT: jne
- br i1 %c, label %34, label %3
-
-; <label>:3: ; preds = %2
- br i1 %c, label %7, label %4
-
-; <label>:4: ; preds = %3
- %5 = tail call i32 @f(i32 undef, i32 undef)
- %6 = icmp eq i32 %5, 0
- br i1 %6, label %7, label %34
-
-; <label>:7: ; preds = %4, %3
- %8 = icmp eq %2* null, null
- br i1 %8, label %34, label %9
-
-; <label>:9: ; preds = %7
- %10 = icmp eq i8* %p1, null
- br i1 %10, label %11, label %32
-
-; <label>:11: ; preds = %9
- %12 = load %2*, %2** %p2, align 8
- %13 = icmp eq %2* %12, null
- br i1 %13, label %34, label %14
-
-; <label>:14: ; preds = %11
- %15 = getelementptr inbounds %2, %2* %12, i64 0, i32 1
- %16 = load i8*, i8** %15, align 8
- %17 = icmp eq i8* %16, null
- br i1 %17, label %18, label %32
-
-; <label>:18: ; preds = %14
- %19 = load %2*, %2** %p2, align 8
- %20 = icmp eq %2* %19, null
- br i1 %20, label %34, label %21
-
-; <label>:21: ; preds = %18
- %22 = getelementptr inbounds %2, %2* %19, i64 0, i32 1
- %23 = load i8*, i8** %22, align 8
- %24 = icmp eq i8* %23, null
- br i1 %24, label %25, label %32
-
-; <label>:25: ; preds = %28, %21
- %26 = load %2*, %2** %p2, align 8
- %27 = icmp eq %2* %26, null
- br i1 %27, label %34, label %28
-
-; <label>:28: ; preds = %25
- %29 = getelementptr inbounds %2, %2* %26, i64 0, i32 1
- %30 = load i8*, i8** %29, align 8
- %31 = icmp eq i8* %30, null
- br i1 %31, label %25, label %32
-
-; <label>:32: ; preds = %28, %21, %14, %9
- %33 = tail call i32 (...) @Up()
- br label %34
-
-; <label>:34: ; preds = %32, %25, %18, %11, %7, %4, %2
- %35 = phi i32 [ 0, %2 ], [ %5, %4 ], [ 0, %7 ], [ 0, %11 ], [ 0, %32 ], [ 0, %18 ], [ 0, %25 ]
- ret i32 %35
-}
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