Bug 20162 – Sign Extension for ?: optimization done wrong

The following code produces weird results: ---- import std.stdio; long f(long a) { return a % 1000000; } void main() { foreach (i; 0 .. 2) { writeln(typeid((i != 0) ? -1 : +1)); writeln(i, " ", ((i != 0) ? -1 : +1), " ", f((i != 0) ? -1 : +1)); } foreach (i; 0 .. 2) { foreach (j; 0 .. 2) { writeln(typeid((i != 0) ? -1 : +1)); writeln(i, " ", j, " ", ((i != 0) ? -1 : +1), " ", f((i != 0) ? -1 : +1)); } } } ---- (https://ideone.com/kyPT72) Its outputs are: int 0 1 1 int 1 -1 -1 int 0 0 1 1 int 0 1 1 1 int 1 0 -1 967295 int 1 1 -1 967295 printing (2^32 - 1) mod 1000000 instead of -1, only for the nested for-loop. This happens only with -m64 and -O options.

A smaller test case: --- import core.stdc.stdio; long f(long a) { return a; } void main() { foreach (i; 1 .. 2) { foreach (j; 0 .. 2) { printf("%d %d %llx\n", i, ((i != 0) ? -1 : +1), f((i != 0) ? -1 : +1)); } } } --- which prints: 1 -1 ffffffff 1 -1 ffffffff

@WalterBright created dlang/dmd pull request #11529 "fix Issue 20162 - Sign Extension for ?: optimization done wrong" fixing this issue: - fix Issue 20162 - Sign Extension for ?: optimization done wrong https://github.com/dlang/dmd/pull/11529

dlang/dmd pull request #11529 "fix Issue 20162 - Sign Extension for ?: optimization done wrong" was merged into master: - a8e77a7de838efa7132179436cce26af047f9ab4 by Walter Bright: fix Issue 20162 - Sign Extension for ?: optimization done wrong https://github.com/dlang/dmd/pull/11529