Clean up the AST for while loops and fix several problems with
cleanups for while loops:
1) Make sure that we destroy the condition variable of a while statement each time through the loop for, e.g.,
while (shared_ptr<WorkInt> p = getWorkItem()) {
// ...
}
2) Make sure that we always enter a new cleanup scope for the body of the while loop, even when there is no compound expression, e.g.,
while (blah)
RAIIObject raii(blah+1);
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@89800 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/CGStmt.cpp b/lib/CodeGen/CGStmt.cpp
index 34e3649..6fddcf6 100644
--- a/lib/CodeGen/CGStmt.cpp
+++ b/lib/CodeGen/CGStmt.cpp
@@ -353,15 +353,37 @@
// body of the loop.
llvm::BasicBlock *ExitBlock = createBasicBlock("while.end");
llvm::BasicBlock *LoopBody = createBasicBlock("while.body");
+ llvm::BasicBlock *CleanupBlock = 0;
+ llvm::BasicBlock *EffectiveExitBlock = ExitBlock;
// Store the blocks to use for break and continue.
BreakContinueStack.push_back(BreakContinue(ExitBlock, LoopHeader));
+ // C++ [stmt.while]p2:
+ // When the condition of a while statement is a declaration, the
+ // scope of the variable that is declared extends from its point
+ // of declaration (3.3.2) to the end of the while statement.
+ // [...]
+ // The object created in a condition is destroyed and created
+ // with each iteration of the loop.
+ CleanupScope ConditionScope(*this);
+
+ if (S.getConditionVariable()) {
+ EmitLocalBlockVarDecl(*S.getConditionVariable());
+
+ // If this condition variable requires cleanups, create a basic
+ // block to handle those cleanups.
+ if (ConditionScope.requiresCleanups()) {
+ CleanupBlock = createBasicBlock("while.cleanup");
+ EffectiveExitBlock = CleanupBlock;
+ }
+ }
+
// Evaluate the conditional in the while header. C99 6.8.5.1: The
// evaluation of the controlling expression takes place before each
// execution of the loop body.
llvm::Value *BoolCondVal = EvaluateExprAsBool(S.getCond());
-
+
// while(1) is common, avoid extra exit blocks. Be sure
// to correctly handle break/continue though.
bool EmitBoolCondBranch = true;
@@ -371,23 +393,39 @@
// As long as the condition is true, go to the loop body.
if (EmitBoolCondBranch)
- Builder.CreateCondBr(BoolCondVal, LoopBody, ExitBlock);
-
+ Builder.CreateCondBr(BoolCondVal, LoopBody, EffectiveExitBlock);
+
// Emit the loop body.
- EmitBlock(LoopBody);
- EmitStmt(S.getBody());
+ {
+ CleanupScope BodyScope(*this);
+ EmitBlock(LoopBody);
+ EmitStmt(S.getBody());
+ }
BreakContinueStack.pop_back();
- // Cycle to the condition.
- EmitBranch(LoopHeader);
+ if (CleanupBlock) {
+ // If we have a cleanup block, jump there to perform cleanups
+ // before looping.
+ EmitBranch(CleanupBlock);
+
+ // Emit the cleanup block, performing cleanups for the condition
+ // and then jumping to either the loop header or the exit block.
+ EmitBlock(CleanupBlock);
+ ConditionScope.ForceCleanup();
+ Builder.CreateCondBr(BoolCondVal, LoopHeader, ExitBlock);
+ } else {
+ // Cycle to the condition.
+ EmitBranch(LoopHeader);
+ }
// Emit the exit block.
EmitBlock(ExitBlock, true);
+
// The LoopHeader typically is just a branch if we skipped emitting
// a branch, try to erase it.
- if (!EmitBoolCondBranch)
+ if (!EmitBoolCondBranch && !CleanupBlock)
SimplifyForwardingBlocks(LoopHeader);
}