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-rw-r--r--llvm/include/llvm/InitializePasses.h1
-rw-r--r--llvm/include/llvm/LinkAllPasses.h1
-rw-r--r--llvm/include/llvm/Transforms/Scalar.h7
-rw-r--r--llvm/lib/Transforms/Scalar/CMakeLists.txt1
-rw-r--r--llvm/lib/Transforms/Scalar/LoopSimplifyCFG.cpp111
-rw-r--r--llvm/lib/Transforms/Scalar/Scalar.cpp5
-rw-r--r--llvm/test/Transforms/LoopSimplifyCFG/merge-header.ll34
7 files changed, 160 insertions, 0 deletions
diff --git a/llvm/include/llvm/InitializePasses.h b/llvm/include/llvm/InitializePasses.h
index a2e345b7e2a..f873fbd19fc 100644
--- a/llvm/include/llvm/InitializePasses.h
+++ b/llvm/include/llvm/InitializePasses.h
@@ -170,6 +170,7 @@ void initializeLoopInterchangePass(PassRegistry &);
void initializeLoopInstSimplifyPass(PassRegistry&);
void initializeLoopRotatePass(PassRegistry&);
void initializeLoopSimplifyPass(PassRegistry&);
+void initializeLoopSimplifyCFGPass(PassRegistry&);
void initializeLoopStrengthReducePass(PassRegistry&);
void initializeGlobalMergePass(PassRegistry&);
void initializeLoopRerollPass(PassRegistry&);
diff --git a/llvm/include/llvm/LinkAllPasses.h b/llvm/include/llvm/LinkAllPasses.h
index 327faac3320..506be581a24 100644
--- a/llvm/include/llvm/LinkAllPasses.h
+++ b/llvm/include/llvm/LinkAllPasses.h
@@ -106,6 +106,7 @@ namespace {
(void) llvm::createLoopExtractorPass();
(void) llvm::createLoopInterchangePass();
(void) llvm::createLoopSimplifyPass();
+ (void) llvm::createLoopSimplifyCFGPass();
(void) llvm::createLoopStrengthReducePass();
(void) llvm::createLoopRerollPass();
(void) llvm::createLoopUnrollPass();
diff --git a/llvm/include/llvm/Transforms/Scalar.h b/llvm/include/llvm/Transforms/Scalar.h
index 018269fced5..798aee9ccf0 100644
--- a/llvm/include/llvm/Transforms/Scalar.h
+++ b/llvm/include/llvm/Transforms/Scalar.h
@@ -476,6 +476,13 @@ FunctionPass *createLoopDistributePass();
//
FunctionPass *createLoopLoadEliminationPass();
+//===----------------------------------------------------------------------===//
+//
+// LoopSimplifyCFG - This pass performs basic CFG simplification on loops,
+// primarily to help other loop passes.
+//
+Pass *createLoopSimplifyCFGPass();
+
} // End llvm namespace
#endif
diff --git a/llvm/lib/Transforms/Scalar/CMakeLists.txt b/llvm/lib/Transforms/Scalar/CMakeLists.txt
index a0ddbd08520..8f8076a9d4c 100644
--- a/llvm/lib/Transforms/Scalar/CMakeLists.txt
+++ b/llvm/lib/Transforms/Scalar/CMakeLists.txt
@@ -24,6 +24,7 @@ add_llvm_library(LLVMScalarOpts
LoopLoadElimination.cpp
LoopRerollPass.cpp
LoopRotation.cpp
+ LoopSimplifyCFG.cpp
LoopStrengthReduce.cpp
LoopUnrollPass.cpp
LoopUnswitch.cpp
diff --git a/llvm/lib/Transforms/Scalar/LoopSimplifyCFG.cpp b/llvm/lib/Transforms/Scalar/LoopSimplifyCFG.cpp
new file mode 100644
index 00000000000..8e066acced1
--- /dev/null
+++ b/llvm/lib/Transforms/Scalar/LoopSimplifyCFG.cpp
@@ -0,0 +1,111 @@
+//===--------- LoopSimplifyCFG.cpp - Loop CFG Simplification Pass ---------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements the Loop SimplifyCFG Pass. This pass is responsible for
+// basic loop CFG cleanup, primarily to assist other loop passes. If you
+// encounter a noncanonical CFG construct that causes another loop pass to
+// perform suboptimally, this is the place to fix it up.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Transforms/Scalar.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/Analysis/AliasAnalysis.h"
+#include "llvm/Analysis/BasicAliasAnalysis.h"
+#include "llvm/Analysis/AssumptionCache.h"
+#include "llvm/Analysis/DependenceAnalysis.h"
+#include "llvm/Analysis/GlobalsModRef.h"
+#include "llvm/Analysis/LoopInfo.h"
+#include "llvm/Analysis/LoopPass.h"
+#include "llvm/Analysis/ScalarEvolution.h"
+#include "llvm/Analysis/ScalarEvolutionAliasAnalysis.h"
+#include "llvm/Analysis/TargetTransformInfo.h"
+#include "llvm/IR/Dominators.h"
+#include "llvm/Transforms/Utils/Local.h"
+using namespace llvm;
+
+#define DEBUG_TYPE "loop-simplifycfg"
+
+namespace {
+class LoopSimplifyCFG : public LoopPass {
+public:
+ static char ID; // Pass ID, replacement for typeid
+ LoopSimplifyCFG() : LoopPass(ID) {
+ initializeLoopSimplifyCFGPass(*PassRegistry::getPassRegistry());
+ }
+
+ bool runOnLoop(Loop *L, LPPassManager &) override;
+
+ void getAnalysisUsage(AnalysisUsage &AU) const override {
+ AU.addRequired<DominatorTreeWrapperPass>();
+ AU.addRequired<LoopInfoWrapperPass>();
+
+ AU.addPreserved<DominatorTreeWrapperPass>();
+ AU.addPreserved<LoopInfoWrapperPass>();
+ AU.addPreserved<GlobalsAAWrapperPass>();
+ AU.addPreserved<BasicAAWrapperPass>();
+ AU.addPreserved<AAResultsWrapperPass>();
+ AU.addPreserved<ScalarEvolutionWrapperPass>();
+ AU.addPreserved<SCEVAAWrapperPass>();
+ AU.addPreserved<DependenceAnalysis>();
+ AU.addPreservedID(LoopSimplifyID);
+ AU.addPreservedID(LCSSAID);
+ }
+};
+}
+
+char LoopSimplifyCFG::ID = 0;
+INITIALIZE_PASS_BEGIN(LoopSimplifyCFG, "loop-simplifycfg", "Simplify loop CFG",
+ false, false)
+INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
+INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)
+INITIALIZE_PASS_END(LoopSimplifyCFG, "loop-simplifycfg", "Simplify loop CFG",
+ false, false)
+
+Pass *llvm::createLoopSimplifyCFGPass() { return new LoopSimplifyCFG(); }
+
+static bool simplifyLoopCFG(Loop *L, DominatorTree *DT, LoopInfo *LI) {
+ bool Changed = false;
+ // Copy blocks into a temporary array to avoid iterator invalidation issues
+ // as we remove them.
+ SmallVector<WeakVH, 16> Blocks(L->blocks());
+
+ for (auto &Block : Blocks) {
+ // Attempt to merge blocks in the trivial case. Don't modify blocks which
+ // belong to other loops.
+ BasicBlock *Succ = cast<BasicBlock>(Block);
+ if (!Succ)
+ continue;
+
+ BasicBlock *Pred = Succ->getSinglePredecessor();
+ if (!Pred || !Pred->getSingleSuccessor() || LI->getLoopFor(Pred) != L)
+ continue;
+
+ // Pred is going to disappear, so we need to update the loop info.
+ if (L->getHeader() == Pred)
+ L->moveToHeader(Succ);
+ LI->removeBlock(Pred);
+ MergeBasicBlockIntoOnlyPred(Succ, DT);
+ Changed = true;
+ }
+
+ return Changed;
+}
+
+/// runOnLoop - Perform basic CFG simplifications to assist other loop passes.
+/// For now, this only attempts to merge blocks in the trivial case.
+bool LoopSimplifyCFG::runOnLoop(Loop *L, LPPassManager &) {
+ if (skipOptnoneFunction(L))
+ return false;
+
+ DominatorTree *DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
+ LoopInfo *LI = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
+ return simplifyLoopCFG(L, DT, LI);
+}
diff --git a/llvm/lib/Transforms/Scalar/Scalar.cpp b/llvm/lib/Transforms/Scalar/Scalar.cpp
index 52d477cc957..f70e685b085 100644
--- a/llvm/lib/Transforms/Scalar/Scalar.cpp
+++ b/llvm/lib/Transforms/Scalar/Scalar.cpp
@@ -84,6 +84,7 @@ void llvm::initializeScalarOpts(PassRegistry &Registry) {
initializeFloat2IntPass(Registry);
initializeLoopDistributePass(Registry);
initializeLoopLoadEliminationPass(Registry);
+ initializeLoopSimplifyCFGPass(Registry);
}
void LLVMInitializeScalarOpts(LLVMPassRegistryRef R) {
@@ -154,6 +155,10 @@ void LLVMAddLoopRerollPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createLoopRerollPass());
}
+void LLVMAddLoopSimplifyCFGPass(LLVMPassManagerRef PM) {
+ unwrap(PM)->add(createLoopSimplifyCFGPass());
+}
+
void LLVMAddLoopUnrollPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createLoopUnrollPass());
}
diff --git a/llvm/test/Transforms/LoopSimplifyCFG/merge-header.ll b/llvm/test/Transforms/LoopSimplifyCFG/merge-header.ll
new file mode 100644
index 00000000000..2e032ef22eb
--- /dev/null
+++ b/llvm/test/Transforms/LoopSimplifyCFG/merge-header.ll
@@ -0,0 +1,34 @@
+; RUN: opt -S -loop-simplifycfg < %s | FileCheck %s
+
+; CHECK-LABEL: foo
+; CHECK: entry:
+; CHECK-NEXT: br label %[[LOOP:[a-z]+]]
+; CHECK: [[LOOP]]:
+; CHECK-NEXT: phi
+; CHECK-NOT: br label
+; CHECK: br i1
+define i32 @foo(i32* %P, i64* %Q) {
+entry:
+ br label %outer
+
+outer: ; preds = %outer.latch2, %entry
+ %y.2 = phi i32 [ 0, %entry ], [ %y.inc2, %outer.latch2 ]
+ br label %inner
+
+inner: ; preds = %outer
+ store i32 0, i32* %P
+ store i32 1, i32* %P
+ store i32 2, i32* %P
+ %y.inc2 = add nsw i32 %y.2, 1
+ %exitcond.outer = icmp eq i32 %y.inc2, 3
+ store i32 %y.2, i32* %P
+ br i1 %exitcond.outer, label %exit, label %outer.latch2
+
+outer.latch2: ; preds = %inner
+ %t = sext i32 %y.inc2 to i64
+ store i64 %t, i64* %Q
+ br label %outer
+
+exit: ; preds = %inner
+ ret i32 0
+}
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