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[AArch64] Move the branch relaxation pass after BTI insertion
Summary:
Inserting BTI instructions can push branch destinations out of range.
The branch relaxation pass itself cannot insert indirect branches since `TargetInstrInfo::insertIndirecrtBranch` is not implemented for AArch64 (guess +/-128 MB direct branch range is more than enough in practice).
Testing this is a bit tricky.
The original test case we have is 155kloc/6.1M. I've generated a test case using this program:
```
int main() {
std::cout << R"src(int test();
void g0(), g1(), g2(), g3(), g4(), e();
void f(int v) {
if ((test() & 2) == 0) {
switch (v) {
case 0:
g0();
case 1:
g1();
case 2:
g2();
case 3:
g3();
}
)src";
const int N = 8176;
for (int i = 0; i < N; ++i)
std::cout << " void h" << i << "();\n";
for (int i = 0; i < N; ++i)
std::cout << " h" << i << "();\n";
std::cout << R"src(
} else {
e();
}
}
)src";
}
```
which is still a bit too much to commit as a regression test, IMHO.
Reviewers: t.p.northover, ostannard
Reviewed By: ostannard
Subscribers: kristof.beyls, hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D69118
Change-Id: Ide5c922bcde08ff4cf635da5e52365525a997a0a