On Thursday, 9 May 2024 at 18:24:12 UTC, Iain Buclaw wrote:
On Wednesday, 8 May 2024 at 14:26:25 UTC, Paul Backus wrote:
When the following program is compiled with GDC 14.1, the
assertion fails:
void main() {
int d = 42;
bool o = d > d++;
assert(o == false);
}
(Godbolt: https://d.godbolt.org/z/e63xbb9Td)
The assertion passes when the program is compiled with DMD
2.108.0.
The same bug was recently reported for LDC:
https://github.com/ldc-developers/ldc/issues/4651
I want to say that rewriting `d > d++` to `d++ < d` is a valid
optimization.
See also `opCmp` rewriting `a < b` into `b.opCmp(a)`
https://dlang.org/spec/operatoroverloading.html#compare
Even when it doesn't swap order, DMD doesn't store the left hand
of the expression to a target/temporary when operator overloading
is involved.
https://d.godbolt.org/z/jYYr1WMhn
```
o = d.opCmp(d.opUnary!"++"())
```
Effectively
```
arg = d.opUnary!"++"(); // d mutates
o = d.opCmp(arg) > 0; // true
```
