https://gcc.gnu.org/bugzilla/show_bug.cgi?id=119491
Bug ID: 119491
Summary: missed tail call due to exceptions which is empty
Product: gcc
Version: 15.0
Status: UNCONFIRMED
Keywords: missed-optimization, tail-call
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: pinskia at gcc dot gnu.org
Blocks: 119376
Target Milestone: ---
Take this C++ code:
```
struct TcFieldData {
struct DefaultInit {};
TcFieldData() {}
};
struct TcParseTableBase;
void target_atomic(TcFieldData data);
template <typename VarintType>
static inline __attribute__((always_inline)) void ShiftMixParseVarint( int
&res1) { }
static inline __attribute__((always_inline)) void ParseVarint(int *value) {
int res = 0;
ShiftMixParseVarint<int>(res);
}
void f();
unsigned char fast_idx_mask;
TcFieldData bits;
inline __attribute__((always_inline)) void TagDispatch(TcFieldData) {
if (fast_idx_mask)
f();
[[clang::musttail]] return target_atomic(bits);
}
void MpUnknownEnumFallback(TcFieldData data) {
int tmp;
ParseVarint(&tmp);
[[clang::musttail]]
return TagDispatch(TcFieldData{});
}
```
The musttail should not fail but currently does since we end up with:
```
<bb 5> [count: 0]:
<L5>:
goto <bb 8>; [100.00%]
...
<bb 7> [count: 0]:
<L4>:
<bb 8> [count: 0]:
<L2>:
resx 1
```
Which should be optimized away. We do optimize it away but after tailc is run.
Note this is reduced from PR 119376 .
Referenced Bugs:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=119376
[Bug 119376] [15 Regression] musttail does not get dropped after inlining?
