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assuem(X) handling in GVN bugfix 

There was infinite loop because it was trying to change assume(true) into
assume(true)
Also added handling when assume(false) appear

http://reviews.llvm.org/D12516

llvm-svn: 246697
This commit is contained in:
Piotr Padlewski 2015-09-02 20:00:03 +00:00
parent 28ffcbe1cc
commit 0c7d8fc1f6
2 changed files with 60 additions and 1 deletions
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21
llvm/lib/Transforms/Scalar/GVN.cpp
View File

@ -1771,8 +1771,24 @@ bool GVN::processAssumeIntrinsic(IntrinsicInst *IntrinsicI) {
assert(IntrinsicI->getIntrinsicID() == Intrinsic::assume &&
"This function can only be called with llvm.assume intrinsic");
Value *V = IntrinsicI->getArgOperand(0);
if (ConstantInt *Cond = dyn_cast<ConstantInt>(V)) {
if (Cond->isZero()) {
Type *Int8Ty = Type::getInt8Ty(V->getContext());
// Insert a new store to null instruction before the load to indicate that
// this code is not reachable. FIXME: We could insert unreachable
// instruction directly because we can modify the CFG.
new StoreInst(UndefValue::get(Int8Ty),
Constant::getNullValue(Int8Ty->getPointerTo()),
IntrinsicI);
}
markInstructionForDeletion(IntrinsicI);
return false;
}
Constant *True = ConstantInt::getTrue(V->getContext());
bool Changed = false;
for (BasicBlock *Successor : successors(IntrinsicI->getParent())) {
BasicBlockEdge Edge(IntrinsicI->getParent(), Successor);
@ -1780,6 +1796,7 @@ bool GVN::processAssumeIntrinsic(IntrinsicInst *IntrinsicI) {
// will check dominance for us.
Changed |= propagateEquality(V, True, Edge, false);
}
// We can replace assume value with true, which covers cases like this:
// call void @llvm.assume(i1 %cmp)
// br i1 %cmp, label %bb1, label %bb2 ; will change %cmp to true
@ -2087,6 +2104,8 @@ bool GVN::replaceOperandsWithConsts(Instruction *Instr) const {
Value *Operand = Instr->getOperand(OpNum);
auto it = ReplaceWithConstMap.find(Operand);
if (it != ReplaceWithConstMap.end()) {
assert(!isa<Constant>(Operand) &&
"Replacing constants with constants is invalid");
Instr->setOperand(OpNum, it->second);
Changed = true;
}
@ -2459,8 +2478,8 @@ bool GVN::processBlock(BasicBlock *BB) {
BI != BE;) {
if (!ReplaceWithConstMap.empty())
ChangedFunction |= replaceOperandsWithConsts(BI);
ChangedFunction |= processInstruction(BI);
if (InstrsToErase.empty()) {
++BI;
continue;

40
llvm/test/Transforms/GVN/assume-equal.ll
View File

@ -122,6 +122,7 @@ entry:
; CHECK: br i1 true, label %bb2, label %bb2
br i1 %cmp, label %bb2, label %bb2
bb2:
call void @llvm.assume(i1 true)
; CHECK: br i1 true, label %bb2, label %bb2
br i1 %cmp, label %bb2, label %bb2
@ -129,6 +130,45 @@ bb2:
ret i32 %p
}
; CHECK-LABEL: define i32 @_Z1ij(i32 %p)
define i32 @_Z1ij(i32 %p) {
entry:
%cmp = icmp eq i32 %p, 42
call void @llvm.assume(i1 %cmp)
; CHECK: br i1 true, label %bb2, label %bb2
br i1 %cmp, label %bb2, label %bb2
bb2:
; CHECK-NOT: %cmp2 =
%cmp2 = icmp eq i32 %p, 42
; CHECK-NOT: call void @llvm.assume(
call void @llvm.assume(i1 %cmp2)
; CHECK: br i1 true, label %bb2, label %bb2
br i1 %cmp, label %bb2, label %bb2
; CHECK: ret i32 42
ret i32 %p
}
; CHECK-LABEL: define i32 @_Z1ik(i32 %p)
define i32 @_Z1ik(i32 %p) {
entry:
%cmp = icmp eq i32 %p, 42
call void @llvm.assume(i1 %cmp)
; CHECK: br i1 true, label %bb2, label %bb3
br i1 %cmp, label %bb2, label %bb3
bb2:
; CHECK-NOT: %cmp3 =
%cmp3 = icmp eq i32 %p, 43
; CHECK: store i8 undef, i8* null
call void @llvm.assume(i1 %cmp3)
ret i32 15
bb3:
ret i32 17
}
declare noalias i8* @_Znwm(i64)
declare void @_ZN1AC1Ev(%struct.A*)
declare void @llvm.assume(i1)