sgatev added inline comments.
================
Comment at: clang/lib/Analysis/FlowSensitive/Transfer.cpp:516
+ // assigned to it.
+ Visit(&SubExpr);
+ if (auto *Val = dyn_cast_or_null<BoolValue>(
----------------
xazax.hun wrote:
> Could you elaborate on when would this happen? I'd expect the traversal to
> always visit the predecessor basic blocks first and within a basic block
> always visit subexpressions first. So I'd be quite surprised if there is a
> subexpression we did not visit.
From what I've seen, logic operators influence the structure of the CFG through
additional basic blocks and terminators, but their sub-expression operators are
not added directly in the basic blocks.
For example:
```
void test(bool a, bool b, bool c) {
bool d = a && (b || c);
}
```
results in:
```
void test(bool a, bool b, bool c)
[B5 (ENTRY)]
Succs (1): B4
[B1]
1: [B4.2] && ([B3.2] || [B2.2])
2: bool d = a && (b || c);
Preds (3): B2 B3 B4
Succs (1): B0
[B2]
1: c
2: [B2.1] (ImplicitCastExpr, LValueToRValue, _Bool)
Preds (1): B3
Succs (1): B1
[B3]
1: b
2: [B3.1] (ImplicitCastExpr, LValueToRValue, _Bool)
T: [B3.2] || ...
Preds (1): B4
Succs (2): B1 B2
[B4]
1: a
2: [B4.1] (ImplicitCastExpr, LValueToRValue, _Bool)
T: [B4.2] && ...
Preds (1): B5
Succs (2): B3 B1
[B0 (EXIT)]
Preds (1): B1
```
So, when we evaluate `a && (b || c)` in `B1`, the sub-expression `b || c` has
not been evaluated yet. I updated the comment in the code to make that more
clear.
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D121455/new/
https://reviews.llvm.org/D121455
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