6502/llvm-6502
1
0
Fork 0
mirror of https://github.com/c64scene-ar/llvm-6502.git synced 2025-06-13 22:24:07 +00:00
Code Issues Projects Releases Wiki Activity

Implement PR1796 and Transforms/SimplifyCFG/noreturn-call.ll

Browse Source 
by inserting unreachable after no-return calls.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@44099 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner
2007-11-14 06:19:25 +00:00
parent 019b92a70c
commit 1b12d8855d
2 changed files with 72 additions and 17 deletions
Download Patch File Download Diff File Expand all files Collapse all files

78
lib/Transforms/Scalar/SimplifyCFG.cpp
View File

@ -24,6 +24,7 @@
#include "llvm/Constants.h" #include "llvm/Constants.h"
#include "llvm/Instructions.h" #include "llvm/Instructions.h"
#include "llvm/Module.h" #include "llvm/Module.h"
#include "llvm/ParameterAttributes.h"
#include "llvm/Support/CFG.h" #include "llvm/Support/CFG.h"
#include "llvm/Support/Compiler.h" #include "llvm/Support/Compiler.h"
#include "llvm/Pass.h" #include "llvm/Pass.h"
@ -50,6 +51,46 @@ FunctionPass *llvm::createCFGSimplificationPass() {
return new CFGSimplifyPass(); 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) {
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);
new UnreachableInst(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++);
}
}
/// IsNoReturn - Return true if the specified call is to a no-return function.
static bool IsNoReturn(const CallInst *CI) {
if (const ParamAttrsList *Attrs = CI->getParamAttrs())
if (Attrs->paramHasAttr(0, ParamAttr::NoReturn))
return true;
if (const Function *Callee = CI->getCalledFunction()) {
if (const ParamAttrsList *Attrs = Callee->getParamAttrs())
if (Attrs->paramHasAttr(0, ParamAttr::NoReturn))
return true;
const FunctionType *FT = Callee->getFunctionType();
if (const ParamAttrsList *Attrs = FT->getParamAttrs())
if (Attrs->paramHasAttr(0, ParamAttr::NoReturn))
return true;
}
return false;
}
static bool MarkAliveBlocks(BasicBlock *BB, static bool MarkAliveBlocks(BasicBlock *BB,
SmallPtrSet<BasicBlock*, 128> &Reachable) { SmallPtrSet<BasicBlock*, 128> &Reachable) {
@ -66,26 +107,29 @@ static bool MarkAliveBlocks(BasicBlock *BB,
// Do a quick scan of the basic block, turning any obviously unreachable // Do a quick scan of the basic block, turning any obviously unreachable
// instructions into LLVM unreachable insts. The instruction combining pass // instructions into LLVM unreachable insts. The instruction combining pass
// canonnicalizes unreachable insts into stores to null or undef. // canonnicalizes unreachable insts into stores to null or undef.
for (BasicBlock::iterator BBI = BB->begin(), E = BB->end(); BBI != E; ++BBI) for (BasicBlock::iterator BBI = BB->begin(), E = BB->end(); BBI != E;++BBI){
if (StoreInst *SI = dyn_cast<StoreInst>(BBI)) if (CallInst *CI = dyn_cast<CallInst>(BBI)) {
if (isa<ConstantPointerNull>(SI->getOperand(1)) || if (IsNoReturn(CI)) {
isa<UndefValue>(SI->getOperand(1))) { // If we found a call to a no-return function, insert an unreachable
// Loop over all of the successors, removing BB's entry from any PHI // instruction after it. Make sure there isn't *already* one there
// nodes. // though.
for (succ_iterator I = succ_begin(BB), SE = succ_end(BB); I != SE;++I) ++BBI;
(*I)->removePredecessor(BB); if (!isa<UnreachableInst>(BBI)) {
ChangeToUnreachable(BBI);
new UnreachableInst(SI); Changed = true;
// All instructions after this are dead.
while (BBI != E) {
if (!BBI->use_empty())
BBI->replaceAllUsesWith(UndefValue::get(BBI->getType()));
BB->getInstList().erase(BBI++);
} }
break; break;
} }
}
if (StoreInst *SI = dyn_cast<StoreInst>(BBI))
if (isa<ConstantPointerNull>(SI->getOperand(1)) ||
isa<UndefValue>(SI->getOperand(1))) {
ChangeToUnreachable(SI);
Changed = true;
break;
}
}
Changed |= ConstantFoldTerminator(BB); Changed |= ConstantFoldTerminator(BB);
for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB); SI != SE; ++SI) for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB); SI != SE; ++SI)

11
test/Transforms/SimplifyCFG/noreturn-call.ll Normal file
View File

@ -0,0 +1,11 @@
; RUN: llvm-as < %s | opt -simplifycfg | llvm-dis | grep unreachable
; PR1796
declare void @Finisher(i32) noreturn
define void @YYY(i32) {
tail call void @Finisher(i32 %0) noreturn
tail call void @Finisher(i32 %0) noreturn
ret void
}