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Make GVN's propagateEquality non-recursive. No intended functionality change. 

The modifications are a lot more trivial than they appear to be in the diff!

llvm-svn: 154174
This commit is contained in:
Duncan Sands 2012-04-06 15:31:09 +00:00
parent 6f86004cbc
commit d12b18f820
1 changed files with 104 additions and 97 deletions
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31
llvm/lib/Transforms/Scalar/GVN.cpp
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@ -1974,12 +1974,19 @@ unsigned GVN::replaceAllDominatedUsesWith(Value *From, Value *To,
/// dominated by 'Root'. Exploit this, for example by replacing 'LHS' with
/// 'RHS' everywhere in the scope. Returns whether a change was made.
bool GVN::propagateEquality(Value *LHS, Value *RHS, BasicBlock *Root) {
if (LHS == RHS) return false;
assert(LHS->getType() == RHS->getType() && "Equal but types differ!");
SmallVector<std::pair<Value*, Value*>, 4> Worklist;
Worklist.push_back(std::make_pair(LHS, RHS));
bool Changed = false;
while (!Worklist.empty()) {
std::pair<Value*, Value*> Item = Worklist.pop_back_val();
LHS = Item.first; RHS = Item.second;
if (LHS == RHS) continue;
assert(LHS->getType() == RHS->getType() && "Equality but unequal types!");
// Don't try to propagate equalities between constants.
if (isa<Constant>(LHS) && isa<Constant>(RHS))
return false;
if (isa<Constant>(LHS) && isa<Constant>(RHS)) continue;
// Prefer a constant on the right-hand side, or an Argument if no constants.
if (isa<Constant>(LHS) || (isa<Argument>(LHS) && !isa<Constant>(RHS)))
@ -2012,7 +2019,6 @@ bool GVN::propagateEquality(Value *LHS, Value *RHS, BasicBlock *Root) {
// Replace all occurrences of 'LHS' with 'RHS' everywhere in the scope. As
// LHS always has at least one use that is not dominated by Root, this will
// never do anything if LHS has only one use.
bool Changed = false;
if (!LHS->hasOneUse()) {
unsigned NumReplacements = replaceAllDominatedUsesWith(LHS, RHS, Root);
Changed |= NumReplacements > 0;
@ -2025,11 +2031,11 @@ bool GVN::propagateEquality(Value *LHS, Value *RHS, BasicBlock *Root) {
// RHS are currently supported.
if (!RHS->getType()->isIntegerTy(1))
// Not a boolean equality - bail out.
return Changed;
continue;
ConstantInt *CI = dyn_cast<ConstantInt>(RHS);
if (!CI)
// RHS neither 'true' nor 'false' - bail out.
return Changed;
continue;
// Whether RHS equals 'true'. Otherwise it equals 'false'.
bool isKnownTrue = CI->isAllOnesValue();
bool isKnownFalse = !isKnownTrue;
@ -2039,9 +2045,9 @@ bool GVN::propagateEquality(Value *LHS, Value *RHS, BasicBlock *Root) {
Value *A, *B;
if ((isKnownTrue && match(LHS, m_And(m_Value(A), m_Value(B)))) ||
(isKnownFalse && match(LHS, m_Or(m_Value(A), m_Value(B))))) {
Changed |= propagateEquality(A, RHS, Root);
Changed |= propagateEquality(B, RHS, Root);
return Changed;
Worklist.push_back(std::make_pair(A, RHS));
Worklist.push_back(std::make_pair(B, RHS));
continue;
}
// If we are propagating an equality like "(A == B)" == "true" then also
@ -2054,7 +2060,7 @@ bool GVN::propagateEquality(Value *LHS, Value *RHS, BasicBlock *Root) {
// A with B everywhere in the scope.
if ((isKnownTrue && Cmp->getPredicate() == CmpInst::ICMP_EQ) ||
(isKnownFalse && Cmp->getPredicate() == CmpInst::ICMP_NE))
Changed |= propagateEquality(Op0, Op1, Root);
Worklist.push_back(std::make_pair(Op0, Op1));
// If "A >= B" is known true, replace "A < B" with false everywhere.
CmpInst::Predicate NotPred = Cmp->getInversePredicate();
@ -2079,7 +2085,8 @@ bool GVN::propagateEquality(Value *LHS, Value *RHS, BasicBlock *Root) {
// is replaced with false.
addToLeaderTable(Num, NotVal, Root);
return Changed;
continue;
}
}
return Changed;