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[SimplifyCFG] Teach FoldBranchToCommonDest() to preserve DomTree, part 1 

... for conditional branch case
This commit is contained in:
Roman Lebedev 2020-12-19 22:23:35 +03:00
parent 262ff9c23e
commit c043f5055e
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GPG Key ID: 083C3EBB4A1689E0
13 changed files with 31 additions and 19 deletions
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3
llvm/include/llvm/Transforms/Utils/Local.h
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@ -201,7 +201,8 @@ bool FlattenCFG(BasicBlock *BB, AAResults *AA = nullptr);
/// If this basic block is ONLY a setcc and a branch, and if a predecessor
/// branches to us and one of our successors, fold the setcc into the
/// predecessor and use logical operations to pick the right destination.
bool FoldBranchToCommonDest(BranchInst *BI, MemorySSAUpdater *MSSAU = nullptr,
bool FoldBranchToCommonDest(BranchInst *BI, llvm::DomTreeUpdater *DTU = nullptr,
MemorySSAUpdater *MSSAU = nullptr,
const TargetTransformInfo *TTI = nullptr,
unsigned BonusInstThreshold = 1);

2
llvm/lib/Transforms/Utils/LoopSimplify.cpp
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@ -681,7 +681,7 @@ ReprocessLoop:
// The block has now been cleared of all instructions except for
// a comparison and a conditional branch. SimplifyCFG may be able
// to fold it now.
if (!FoldBranchToCommonDest(BI, MSSAU))
if (!FoldBranchToCommonDest(BI, /*DTU=*/nullptr, MSSAU))
continue;
// Success. The block is now dead, so remove it from the loop,

17
llvm/lib/Transforms/Utils/SimplifyCFG.cpp
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@ -2743,7 +2743,8 @@ static bool extractPredSuccWeights(BranchInst *PBI, BranchInst *BI,
/// If this basic block is simple enough, and if a predecessor branches to us
/// and one of our successors, fold the block into the predecessor and use
/// logical operations to pick the right destination.
bool llvm::FoldBranchToCommonDest(BranchInst *BI, MemorySSAUpdater *MSSAU,
bool llvm::FoldBranchToCommonDest(BranchInst *BI, DomTreeUpdater *DTU,
MemorySSAUpdater *MSSAU,
const TargetTransformInfo *TTI,
unsigned BonusInstThreshold) {
BasicBlock *BB = BI->getParent();
@ -2907,6 +2908,8 @@ bool llvm::FoldBranchToCommonDest(BranchInst *BI, MemorySSAUpdater *MSSAU,
LLVM_DEBUG(dbgs() << "FOLDING BRANCH TO COMMON DEST:\n" << *PBI << *BB);
Changed = true;
SmallVector<DominatorTree::UpdateType, 3> Updates;
IRBuilder<> Builder(PBI);
// The builder is used to create instructions to eliminate the branch in BB.
// If BB's terminator has !annotation metadata, add it to the new
@ -3055,6 +3058,9 @@ bool llvm::FoldBranchToCommonDest(BranchInst *BI, MemorySSAUpdater *MSSAU,
setBranchWeights(PBI, MDWeights[0], MDWeights[1]);
} else
PBI->setMetadata(LLVMContext::MD_prof, nullptr);
Updates.push_back({DominatorTree::Delete, PredBlock, BB});
Updates.push_back({DominatorTree::Insert, PredBlock, UniqueSucc});
} else {
// Update PHI nodes in the common successors.
for (unsigned i = 0, e = PHIs.size(); i != e; ++i) {
@ -3102,6 +3108,9 @@ bool llvm::FoldBranchToCommonDest(BranchInst *BI, MemorySSAUpdater *MSSAU,
PBI = New_PBI;
}
if (DTU)
DTU->applyUpdatesPermissive(Updates);
// If BI was a loop latch, it may have had associated loop metadata.
// We need to copy it to the new latch, that is, PBI.
if (MDNode *LoopMD = BI->getMetadata(LLVMContext::MD_loop))
@ -6194,7 +6203,8 @@ bool SimplifyCFGOpt::simplifyUncondBranch(BranchInst *BI,
// branches to us and our successor, fold the comparison into the
// predecessor and use logical operations to update the incoming value
// for PHI nodes in common successor.
if (FoldBranchToCommonDest(BI, nullptr, &TTI, Options.BonusInstThreshold))
if (FoldBranchToCommonDest(BI, DTU, /*MSSAU=*/nullptr, &TTI,
Options.BonusInstThreshold))
return requestResimplify();
return false;
}
@ -6257,7 +6267,8 @@ bool SimplifyCFGOpt::simplifyCondBranch(BranchInst *BI, IRBuilder<> &Builder) {
// If this basic block is ONLY a compare and a branch, and if a predecessor
// branches to us and one of our successors, fold the comparison into the
// predecessor and use logical operations to pick the right destination.
if (FoldBranchToCommonDest(BI, nullptr, &TTI, Options.BonusInstThreshold))
if (FoldBranchToCommonDest(BI, DTU, /*MSSAU=*/nullptr, &TTI,
Options.BonusInstThreshold))
return requestResimplify();
// We have a conditional branch to two blocks that are only reachable

2
llvm/test/Transforms/LoopVectorize/if-pred-non-void.ll
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@ -1,4 +1,4 @@
; RUN: opt -S -force-vector-width=2 -force-vector-interleave=1 -loop-vectorize -verify-loop-info -simplifycfg < %s | FileCheck %s
; RUN: opt -S -force-vector-width=2 -force-vector-interleave=1 -loop-vectorize -verify-loop-info -simplifycfg -simplifycfg-require-and-preserve-domtree=1 < %s | FileCheck %s
; RUN: opt -S -force-vector-width=1 -force-vector-interleave=2 -loop-vectorize -verify-loop-info < %s | FileCheck %s --check-prefix=UNROLL-NO-VF
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"

2
llvm/test/Transforms/SimplifyCFG/2006-12-08-Ptr-ICmp-Branch.ll
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@ -1,4 +1,4 @@
; RUN: opt < %s -simplifycfg | llvm-dis
; RUN: opt < %s -simplifycfg -simplifycfg-require-and-preserve-domtree=1 | llvm-dis
; END.
; ModuleID = '2006-12-08-Ptr-ICmp-Branch.ll'

6
llvm/test/Transforms/SimplifyCFG/ARM/branch-fold-threshold.ll
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@ -1,7 +1,7 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt -mtriple=thumbv8m.main %s -simplifycfg -S | FileCheck %s --check-prefix=CHECK --check-prefix=THUMB
; RUN: opt -mtriple=thumbv8a %s -simplifycfg -S | FileCheck %s --check-prefix=CHECK --check-prefix=THUMB
; RUN: opt -mtriple=armv8a %s -simplifycfg -S | FileCheck %s --check-prefix=CHECK --check-prefix=ARM
; RUN: opt -mtriple=thumbv8m.main %s -simplifycfg -simplifycfg-require-and-preserve-domtree=1 -S | FileCheck %s --check-prefix=CHECK --check-prefix=THUMB
; RUN: opt -mtriple=thumbv8a %s -simplifycfg -simplifycfg-require-and-preserve-domtree=1 -S | FileCheck %s --check-prefix=CHECK --check-prefix=THUMB
; RUN: opt -mtriple=armv8a %s -simplifycfg -simplifycfg-require-and-preserve-domtree=1 -S | FileCheck %s --check-prefix=CHECK --check-prefix=ARM
define i32 @foo(i32 %a, i32 %b, i32 %c, i32 %d, i32* %input) {
; CHECK-LABEL: @foo(

2
llvm/test/Transforms/SimplifyCFG/annotations.ll
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@ -1,4 +1,4 @@
; RUN: opt -simplifycfg -S %s | FileCheck --match-full-lines %s
; RUN: opt -simplifycfg -simplifycfg-require-and-preserve-domtree=1 -S %s | FileCheck --match-full-lines %s
; The branch in %cont has !annotation metadata. Make sure generated AND
; has !annotation metadata.

2
llvm/test/Transforms/SimplifyCFG/basictest.ll
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@ -1,6 +1,6 @@
; Test CFG simplify removal of branch instructions.
;
; RUN: opt < %s -simplifycfg -S | FileCheck %s
; RUN: opt < %s -simplifycfg -simplifycfg-require-and-preserve-domtree=1 -S | FileCheck %s
; RUN: opt < %s -passes=simplify-cfg -S | FileCheck %s
define void @test1() {

2
llvm/test/Transforms/SimplifyCFG/branch-fold-dbg.ll
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@ -1,4 +1,4 @@
; RUN: opt -simplifycfg -S < %s | FileCheck %s
; RUN: opt -simplifycfg -simplifycfg-require-and-preserve-domtree=1 -S < %s | FileCheck %s
%0 = type { i32*, i32* }

6
llvm/test/Transforms/SimplifyCFG/branch-fold-threshold.ll
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@ -1,6 +1,6 @@
; RUN: opt %s -simplifycfg -S | FileCheck %s --check-prefix=NORMAL
; RUN: opt %s -simplifycfg -S -bonus-inst-threshold=2 | FileCheck %s --check-prefix=AGGRESSIVE
; RUN: opt %s -simplifycfg -S -bonus-inst-threshold=4 | FileCheck %s --check-prefix=WAYAGGRESSIVE
; RUN: opt %s -simplifycfg -simplifycfg-require-and-preserve-domtree=1 -S | FileCheck %s --check-prefix=NORMAL
; RUN: opt %s -simplifycfg -simplifycfg-require-and-preserve-domtree=1 -S -bonus-inst-threshold=2 | FileCheck %s --check-prefix=AGGRESSIVE
; RUN: opt %s -simplifycfg -simplifycfg-require-and-preserve-domtree=1 -S -bonus-inst-threshold=4 | FileCheck %s --check-prefix=WAYAGGRESSIVE
; RUN: opt %s -passes=simplify-cfg -S | FileCheck %s --check-prefix=NORMAL
; RUN: opt %s -passes='simplify-cfg<bonus-inst-threshold=2>' -S | FileCheck %s --check-prefix=AGGRESSIVE
; RUN: opt %s -passes='simplify-cfg<bonus-inst-threshold=4>' -S | FileCheck %s --check-prefix=WAYAGGRESSIVE

2
llvm/test/Transforms/SimplifyCFG/common-dest-folding.ll
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@ -1,4 +1,4 @@
; RUN: opt < %s -simplifycfg -S | FileCheck %s
; RUN: opt < %s -simplifycfg -simplifycfg-require-and-preserve-domtree=1 -S | FileCheck %s
;CHECK: @foo
;CHECK: and i32 %c1, %k

2
llvm/test/Transforms/SimplifyCFG/fold-branch-to-common-dest.ll
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@ -1,5 +1,5 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt < %s -S -simplifycfg -bonus-inst-threshold=10 | FileCheck %s
; RUN: opt < %s -S -simplifycfg -simplifycfg-require-and-preserve-domtree=1 -bonus-inst-threshold=10 | FileCheck %s
declare void @sideeffect0()
declare void @sideeffect1()

2
llvm/test/Transforms/SimplifyCFG/fold-debug-location.ll
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@ -1,4 +1,4 @@
; RUN: opt -S -simplifycfg < %s | FileCheck %s --match-full-lines
; RUN: opt -S -simplifycfg -simplifycfg-require-and-preserve-domtree=1 < %s | FileCheck %s --match-full-lines
; Make sure we reset the debug location when folding instructions.
; CHECK: [[VAL:%.*]] = and i32 %c2, %k