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Fix EmitCaseStmtRange to ignore empty ranges 

- Also cleaned up emission slightly 
 - Inspection of the code revealed several other bugs, however. Case
   ranges are not properly wired and can result in switch cases being
   dropped or even infinite loops. See: <rdar://problem/6098585>

Completes: <rdar://problem/6094119>
llvm-svn: 53975
This commit is contained in:
Daniel Dunbar 2008-07-24 01:18:41 +00:00
parent 908fccc6ea
commit 2e0f1cd00c
1 changed files with 14 additions and 16 deletions
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30
clang/lib/CodeGen/CGStmt.cpp
View File

@ -420,27 +420,25 @@ void CodeGenFunction::EmitContinueStmt() {
/// add multiple cases to switch instruction, one for each value within
/// the range. If range is too big then emit "if" condition check.
void CodeGenFunction::EmitCaseStmtRange(const CaseStmt &S) {
assert (S.getRHS() && "Unexpected RHS value in CaseStmt");
assert(S.getRHS() && "Expected RHS value in CaseStmt");
const Expr *L = S.getLHS();
const Expr *R = S.getRHS();
llvm::ConstantInt *LV = cast<llvm::ConstantInt>(EmitScalarExpr(L));
llvm::ConstantInt *RV = cast<llvm::ConstantInt>(EmitScalarExpr(R));
llvm::APInt LHS = LV->getValue();
const llvm::APInt &RHS = RV->getValue();
llvm::APSInt LHS = S.getLHS()->getIntegerConstantExprValue(getContext());
llvm::APSInt RHS = S.getRHS()->getIntegerConstantExprValue(getContext());
// If range is empty, do nothing.
if (LHS.isSigned() ? RHS.slt(LHS) : RHS.ult(LHS))
return;
llvm::APInt Range = RHS - LHS;
// FIXME: parameters such as this should not be hardcoded
if (Range.ult(llvm::APInt(Range.getBitWidth(), 64))) {
// Range is small enough to add multiple switch instruction cases.
StartBlock("sw.bb");
llvm::BasicBlock *CaseDest = Builder.GetInsertBlock();
SwitchInsn->addCase(LV, CaseDest);
LHS++;
while (LHS != RHS) {
for (unsigned i = 0, e = Range.getZExtValue() + 1; i != e; ++i) {
SwitchInsn->addCase(llvm::ConstantInt::get(LHS), CaseDest);
LHS++;
}
SwitchInsn->addCase(RV, CaseDest);
EmitStmt(S.getSubStmt());
return;
}
@ -463,7 +461,8 @@ void CodeGenFunction::EmitCaseStmtRange(const CaseStmt &S) {
// Emit range check.
llvm::Value *Diff =
Builder.CreateSub(SwitchInsn->getCondition(), LV, "tmp");
Builder.CreateSub(SwitchInsn->getCondition(), llvm::ConstantInt::get(LHS),
"tmp");
llvm::Value *Cond =
Builder.CreateICmpULE(Diff, llvm::ConstantInt::get(Range), "tmp");
Builder.CreateCondBr(Cond, CaseDest, FalseDest);
@ -481,10 +480,9 @@ void CodeGenFunction::EmitCaseStmt(const CaseStmt &S) {
StartBlock("sw.bb");
llvm::BasicBlock *CaseDest = Builder.GetInsertBlock();
llvm::APSInt CaseVal(32);
S.getLHS()->isIntegerConstantExpr(CaseVal, getContext());
llvm::ConstantInt *LV = llvm::ConstantInt::get(CaseVal);
SwitchInsn->addCase(LV, CaseDest);
llvm::APSInt CaseVal = S.getLHS()->getIntegerConstantExprValue(getContext());
SwitchInsn->addCase(llvm::ConstantInt::get(CaseVal),
CaseDest);
EmitStmt(S.getSubStmt());
}