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-rw-r--r--lib/Transforms/Scalar/SimplifyCFGPass.cpp165
-rw-r--r--lib/Transforms/Utils/Local.cpp147
-rw-r--r--test/Instrumentation/DataFlowSanitizer/args-unreachable-bb.ll14
3 files changed, 152 insertions, 174 deletions
diff --git a/lib/Transforms/Scalar/SimplifyCFGPass.cpp b/lib/Transforms/Scalar/SimplifyCFGPass.cpp
index 6d05640..8371f6d 100644
--- a/lib/Transforms/Scalar/SimplifyCFGPass.cpp
+++ b/lib/Transforms/Scalar/SimplifyCFGPass.cpp
@@ -66,161 +66,6 @@ FunctionPass *llvm::createCFGSimplificationPass() {
return new CFGSimplifyPass();
}
-/// changeToUnreachable - Insert an unreachable instruction before the specified
-/// instruction, making it and the rest of the code in the block dead.
-static void changeToUnreachable(Instruction *I, bool UseLLVMTrap) {
- BasicBlock *BB = I->getParent();
- // Loop over all of the successors, removing BB's entry from any PHI
- // nodes.
- for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB); SI != SE; ++SI)
- (*SI)->removePredecessor(BB);
-
- // Insert a call to llvm.trap right before this. This turns the undefined
- // behavior into a hard fail instead of falling through into random code.
- if (UseLLVMTrap) {
- Function *TrapFn =
- Intrinsic::getDeclaration(BB->getParent()->getParent(), Intrinsic::trap);
- CallInst *CallTrap = CallInst::Create(TrapFn, "", I);
- CallTrap->setDebugLoc(I->getDebugLoc());
- }
- new UnreachableInst(I->getContext(), I);
-
- // All instructions after this are dead.
- BasicBlock::iterator BBI = I, BBE = BB->end();
- while (BBI != BBE) {
- if (!BBI->use_empty())
- BBI->replaceAllUsesWith(UndefValue::get(BBI->getType()));
- BB->getInstList().erase(BBI++);
- }
-}
-
-/// changeToCall - Convert the specified invoke into a normal call.
-static void changeToCall(InvokeInst *II) {
- SmallVector<Value*, 8> Args(II->op_begin(), II->op_end() - 3);
- CallInst *NewCall = CallInst::Create(II->getCalledValue(), Args, "", II);
- NewCall->takeName(II);
- NewCall->setCallingConv(II->getCallingConv());
- NewCall->setAttributes(II->getAttributes());
- NewCall->setDebugLoc(II->getDebugLoc());
- II->replaceAllUsesWith(NewCall);
-
- // Follow the call by a branch to the normal destination.
- BranchInst::Create(II->getNormalDest(), II);
-
- // Update PHI nodes in the unwind destination
- II->getUnwindDest()->removePredecessor(II->getParent());
- II->eraseFromParent();
-}
-
-static bool markAliveBlocks(BasicBlock *BB,
- SmallPtrSet<BasicBlock*, 128> &Reachable) {
-
- SmallVector<BasicBlock*, 128> Worklist;
- Worklist.push_back(BB);
- Reachable.insert(BB);
- bool Changed = false;
- do {
- BB = Worklist.pop_back_val();
-
- // Do a quick scan of the basic block, turning any obviously unreachable
- // instructions into LLVM unreachable insts. The instruction combining pass
- // canonicalizes unreachable insts into stores to null or undef.
- for (BasicBlock::iterator BBI = BB->begin(), E = BB->end(); BBI != E;++BBI){
- if (CallInst *CI = dyn_cast<CallInst>(BBI)) {
- if (CI->doesNotReturn()) {
- // If we found a call to a no-return function, insert an unreachable
- // instruction after it. Make sure there isn't *already* one there
- // though.
- ++BBI;
- if (!isa<UnreachableInst>(BBI)) {
- // Don't insert a call to llvm.trap right before the unreachable.
- changeToUnreachable(BBI, false);
- Changed = true;
- }
- break;
- }
- }
-
- // Store to undef and store to null are undefined and used to signal that
- // they should be changed to unreachable by passes that can't modify the
- // CFG.
- if (StoreInst *SI = dyn_cast<StoreInst>(BBI)) {
- // Don't touch volatile stores.
- if (SI->isVolatile()) continue;
-
- Value *Ptr = SI->getOperand(1);
-
- if (isa<UndefValue>(Ptr) ||
- (isa<ConstantPointerNull>(Ptr) &&
- SI->getPointerAddressSpace() == 0)) {
- changeToUnreachable(SI, true);
- Changed = true;
- break;
- }
- }
- }
-
- // Turn invokes that call 'nounwind' functions into ordinary calls.
- if (InvokeInst *II = dyn_cast<InvokeInst>(BB->getTerminator())) {
- Value *Callee = II->getCalledValue();
- if (isa<ConstantPointerNull>(Callee) || isa<UndefValue>(Callee)) {
- changeToUnreachable(II, true);
- Changed = true;
- } else if (II->doesNotThrow()) {
- if (II->use_empty() && II->onlyReadsMemory()) {
- // jump to the normal destination branch.
- BranchInst::Create(II->getNormalDest(), II);
- II->getUnwindDest()->removePredecessor(II->getParent());
- II->eraseFromParent();
- } else
- changeToCall(II);
- Changed = true;
- }
- }
-
- Changed |= ConstantFoldTerminator(BB, true);
- for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB); SI != SE; ++SI)
- if (Reachable.insert(*SI))
- Worklist.push_back(*SI);
- } while (!Worklist.empty());
- return Changed;
-}
-
-/// removeUnreachableBlocksFromFn - Remove blocks that are not reachable, even
-/// if they are in a dead cycle. Return true if a change was made, false
-/// otherwise.
-static bool removeUnreachableBlocksFromFn(Function &F) {
- SmallPtrSet<BasicBlock*, 128> Reachable;
- bool Changed = markAliveBlocks(F.begin(), Reachable);
-
- // If there are unreachable blocks in the CFG...
- if (Reachable.size() == F.size())
- return Changed;
-
- assert(Reachable.size() < F.size());
- NumSimpl += F.size()-Reachable.size();
-
- // Loop over all of the basic blocks that are not reachable, dropping all of
- // their internal references...
- for (Function::iterator BB = ++F.begin(), E = F.end(); BB != E; ++BB) {
- if (Reachable.count(BB))
- continue;
-
- for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB); SI != SE; ++SI)
- if (Reachable.count(*SI))
- (*SI)->removePredecessor(BB);
- BB->dropAllReferences();
- }
-
- for (Function::iterator I = ++F.begin(); I != F.end();)
- if (!Reachable.count(I))
- I = F.getBasicBlockList().erase(I);
- else
- ++I;
-
- return true;
-}
-
/// mergeEmptyReturnBlocks - If we have more than one empty (other than phi
/// node) return blocks, merge them together to promote recursive block merging.
static bool mergeEmptyReturnBlocks(Function &F) {
@@ -325,7 +170,7 @@ static bool iterativelySimplifyCFG(Function &F, const TargetTransformInfo &TTI,
bool CFGSimplifyPass::runOnFunction(Function &F) {
const TargetTransformInfo &TTI = getAnalysis<TargetTransformInfo>();
const DataLayout *TD = getAnalysisIfAvailable<DataLayout>();
- bool EverChanged = removeUnreachableBlocksFromFn(F);
+ bool EverChanged = removeUnreachableBlocks(F);
EverChanged |= mergeEmptyReturnBlocks(F);
EverChanged |= iterativelySimplifyCFG(F, TTI, TD);
@@ -333,16 +178,16 @@ bool CFGSimplifyPass::runOnFunction(Function &F) {
if (!EverChanged) return false;
// iterativelySimplifyCFG can (rarely) make some loops dead. If this happens,
- // removeUnreachableBlocksFromFn is needed to nuke them, which means we should
+ // removeUnreachableBlocks is needed to nuke them, which means we should
// iterate between the two optimizations. We structure the code like this to
// avoid reruning iterativelySimplifyCFG if the second pass of
- // removeUnreachableBlocksFromFn doesn't do anything.
- if (!removeUnreachableBlocksFromFn(F))
+ // removeUnreachableBlocks doesn't do anything.
+ if (!removeUnreachableBlocks(F))
return true;
do {
EverChanged = iterativelySimplifyCFG(F, TTI, TD);
- EverChanged |= removeUnreachableBlocksFromFn(F);
+ EverChanged |= removeUnreachableBlocks(F);
} while (EverChanged);
return true;
diff --git a/lib/Transforms/Utils/Local.cpp b/lib/Transforms/Utils/Local.cpp
index 08e1808..4db3a72 100644
--- a/lib/Transforms/Utils/Local.cpp
+++ b/lib/Transforms/Utils/Local.cpp
@@ -16,6 +16,7 @@
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallPtrSet.h"
+#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/Dominators.h"
#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/Analysis/MemoryBuiltins.h"
@@ -43,6 +44,8 @@
#include "llvm/Support/raw_ostream.h"
using namespace llvm;
+STATISTIC(NumRemoved, "Number of unreachable basic blocks removed");
+
//===----------------------------------------------------------------------===//
// Local constant propagation.
//
@@ -1121,33 +1124,153 @@ bool llvm::replaceDbgDeclareForAlloca(AllocaInst *AI, Value *NewAllocaAddress,
return true;
}
-bool llvm::removeUnreachableBlocks(Function &F) {
- SmallPtrSet<BasicBlock*, 16> Reachable;
+/// changeToUnreachable - Insert an unreachable instruction before the specified
+/// instruction, making it and the rest of the code in the block dead.
+static void changeToUnreachable(Instruction *I, bool UseLLVMTrap) {
+ BasicBlock *BB = I->getParent();
+ // Loop over all of the successors, removing BB's entry from any PHI
+ // nodes.
+ for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB); SI != SE; ++SI)
+ (*SI)->removePredecessor(BB);
+
+ // Insert a call to llvm.trap right before this. This turns the undefined
+ // behavior into a hard fail instead of falling through into random code.
+ if (UseLLVMTrap) {
+ Function *TrapFn =
+ Intrinsic::getDeclaration(BB->getParent()->getParent(), Intrinsic::trap);
+ CallInst *CallTrap = CallInst::Create(TrapFn, "", I);
+ CallTrap->setDebugLoc(I->getDebugLoc());
+ }
+ new UnreachableInst(I->getContext(), I);
+
+ // All instructions after this are dead.
+ BasicBlock::iterator BBI = I, BBE = BB->end();
+ while (BBI != BBE) {
+ if (!BBI->use_empty())
+ BBI->replaceAllUsesWith(UndefValue::get(BBI->getType()));
+ BB->getInstList().erase(BBI++);
+ }
+}
+
+/// changeToCall - Convert the specified invoke into a normal call.
+static void changeToCall(InvokeInst *II) {
+ SmallVector<Value*, 8> Args(II->op_begin(), II->op_end() - 3);
+ CallInst *NewCall = CallInst::Create(II->getCalledValue(), Args, "", II);
+ NewCall->takeName(II);
+ NewCall->setCallingConv(II->getCallingConv());
+ NewCall->setAttributes(II->getAttributes());
+ NewCall->setDebugLoc(II->getDebugLoc());
+ II->replaceAllUsesWith(NewCall);
+
+ // Follow the call by a branch to the normal destination.
+ BranchInst::Create(II->getNormalDest(), II);
+
+ // Update PHI nodes in the unwind destination
+ II->getUnwindDest()->removePredecessor(II->getParent());
+ II->eraseFromParent();
+}
+
+static bool markAliveBlocks(BasicBlock *BB,
+ SmallPtrSet<BasicBlock*, 128> &Reachable) {
+
SmallVector<BasicBlock*, 128> Worklist;
- Worklist.push_back(&F.getEntryBlock());
- Reachable.insert(&F.getEntryBlock());
+ Worklist.push_back(BB);
+ Reachable.insert(BB);
+ bool Changed = false;
do {
- BasicBlock *BB = Worklist.pop_back_val();
+ BB = Worklist.pop_back_val();
+
+ // Do a quick scan of the basic block, turning any obviously unreachable
+ // instructions into LLVM unreachable insts. The instruction combining pass
+ // canonicalizes unreachable insts into stores to null or undef.
+ for (BasicBlock::iterator BBI = BB->begin(), E = BB->end(); BBI != E;++BBI){
+ if (CallInst *CI = dyn_cast<CallInst>(BBI)) {
+ if (CI->doesNotReturn()) {
+ // If we found a call to a no-return function, insert an unreachable
+ // instruction after it. Make sure there isn't *already* one there
+ // though.
+ ++BBI;
+ if (!isa<UnreachableInst>(BBI)) {
+ // Don't insert a call to llvm.trap right before the unreachable.
+ changeToUnreachable(BBI, false);
+ Changed = true;
+ }
+ break;
+ }
+ }
+
+ // Store to undef and store to null are undefined and used to signal that
+ // they should be changed to unreachable by passes that can't modify the
+ // CFG.
+ if (StoreInst *SI = dyn_cast<StoreInst>(BBI)) {
+ // Don't touch volatile stores.
+ if (SI->isVolatile()) continue;
+
+ Value *Ptr = SI->getOperand(1);
+
+ if (isa<UndefValue>(Ptr) ||
+ (isa<ConstantPointerNull>(Ptr) &&
+ SI->getPointerAddressSpace() == 0)) {
+ changeToUnreachable(SI, true);
+ Changed = true;
+ break;
+ }
+ }
+ }
+
+ // Turn invokes that call 'nounwind' functions into ordinary calls.
+ if (InvokeInst *II = dyn_cast<InvokeInst>(BB->getTerminator())) {
+ Value *Callee = II->getCalledValue();
+ if (isa<ConstantPointerNull>(Callee) || isa<UndefValue>(Callee)) {
+ changeToUnreachable(II, true);
+ Changed = true;
+ } else if (II->doesNotThrow()) {
+ if (II->use_empty() && II->onlyReadsMemory()) {
+ // jump to the normal destination branch.
+ BranchInst::Create(II->getNormalDest(), II);
+ II->getUnwindDest()->removePredecessor(II->getParent());
+ II->eraseFromParent();
+ } else
+ changeToCall(II);
+ Changed = true;
+ }
+ }
+
+ Changed |= ConstantFoldTerminator(BB, true);
for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB); SI != SE; ++SI)
if (Reachable.insert(*SI))
Worklist.push_back(*SI);
} while (!Worklist.empty());
+ return Changed;
+}
+
+/// removeUnreachableBlocksFromFn - Remove blocks that are not reachable, even
+/// if they are in a dead cycle. Return true if a change was made, false
+/// otherwise.
+bool llvm::removeUnreachableBlocks(Function &F) {
+ SmallPtrSet<BasicBlock*, 128> Reachable;
+ bool Changed = markAliveBlocks(F.begin(), Reachable);
+ // If there are unreachable blocks in the CFG...
if (Reachable.size() == F.size())
- return false;
+ return Changed;
assert(Reachable.size() < F.size());
- for (Function::iterator I = llvm::next(F.begin()), E = F.end(); I != E; ++I) {
- if (Reachable.count(I))
+ NumRemoved += F.size()-Reachable.size();
+
+ // Loop over all of the basic blocks that are not reachable, dropping all of
+ // their internal references...
+ for (Function::iterator BB = ++F.begin(), E = F.end(); BB != E; ++BB) {
+ if (Reachable.count(BB))
continue;
- for (succ_iterator SI = succ_begin(I), SE = succ_end(I); SI != SE; ++SI)
+ for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB); SI != SE; ++SI)
if (Reachable.count(*SI))
- (*SI)->removePredecessor(I);
- I->dropAllReferences();
+ (*SI)->removePredecessor(BB);
+ BB->dropAllReferences();
}
- for (Function::iterator I = llvm::next(F.begin()), E=F.end(); I != E;)
+ for (Function::iterator I = ++F.begin(); I != F.end();)
if (!Reachable.count(I))
I = F.getBasicBlockList().erase(I);
else
diff --git a/test/Instrumentation/DataFlowSanitizer/args-unreachable-bb.ll b/test/Instrumentation/DataFlowSanitizer/args-unreachable-bb.ll
index db3dd83..b91f321 100644
--- a/test/Instrumentation/DataFlowSanitizer/args-unreachable-bb.ll
+++ b/test/Instrumentation/DataFlowSanitizer/args-unreachable-bb.ll
@@ -1,8 +1,8 @@
; RUN: opt < %s -dfsan -verify -dfsan-args-abi -S | FileCheck %s
target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
-define i8 @unreachable_bb() {
- ; CHECK: @unreachable_bb
+; CHECK-LABEL: @unreachable_bb1
+define i8 @unreachable_bb1() {
; CHECK: ret { i8, i16 } { i8 1, i16 0 }
; CHECK-NOT: bb2:
; CHECK-NOT: bb3:
@@ -18,3 +18,13 @@ bb3:
bb4:
br label %bb3
}
+
+declare void @abort() noreturn
+
+; CHECK-LABEL: @unreachable_bb2
+define i8 @unreachable_bb2() {
+ call void @abort() noreturn
+ ; CHECK-NOT: i8 12
+ ; CHECK: unreachable
+ ret i8 12
+}
generated by cgit v1.1 at 2024-12-22 22:17:01 +0000