lebedev.ri added inline comments.
================
Comment at: lib/CodeGen/CGExprScalar.cpp:1694
// handle things like function to ptr-to-function decay etc.
Value *ScalarExprEmitter::VisitCastExpr(CastExpr *CE) {
Expr *E = CE->getSubExpr();
----------------
vsk wrote:
> lebedev.ri wrote:
> > vsk wrote:
> > > I think maintaining a stack of visited cast exprs in the emitter be
> > > cheaper/simpler than using ASTContext::getParents. You could push CE here
> > > and use a RAII helper to pop it. The 'isCastPartOfExplicitCast' check
> > > then simplifies to a quick stack traversal.
> > Hmm, two things come to mind:
> > 1. This pessimizes the (most popular) case when the sanitizer is disabled.
> > 2. `ASTContext::getParents()` may return more than one parent. I'm not sure
> > if that matters here?
> > I'll take a look..
> As for (1), it's not necessary to push/pop the stack when this sanitizer is
> disabled. And for (2), IIUC the only interesting case is "explicit-cast
> <implicit-cast>+", and none of the implicit casts here have more than one
> parent.
> I think maintaining a stack of visited cast exprs in the emitter be
> cheaper/simpler than using ASTContext::getParents.
{F6660377}
So yeah, this could work.
Except sadly it breaks in subtle cases like https://godbolt.org/g/5V2czU
I have added those tests beforehand.
Is `ASTContext::getParents()` really horribly slow so we want to
duplicate/maintain/track
the current AST stack ourselves?
If so, we will need to maintain the *entire* stack, not just `CastExpr''s...
Repository:
rC Clang
https://reviews.llvm.org/D48958
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