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[AArch64] Make AArch64A57FPLoadBalancing output stable. 

Add tie breaker to colorChainSet() sort so that processing order doesn't
depend on std::set order, which depends on pointer order, which is
unstable from run to run.

No test case as this is nearly impossible to reproduce.

Phabricator Review: http://reviews.llvm.org/D7265
Patch by Geoff Berry <gberry@codeaurora.org>!

llvm-svn: 227606
This commit is contained in:
Chad Rosier 2015-01-30 19:55:40 +00:00
parent 133e102b8f
commit b23c4dd3a4
1 changed files with 9 additions and 2 deletions
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9
llvm/lib/Target/AArch64/AArch64A57FPLoadBalancing.cpp
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@ -272,7 +272,7 @@ public:
}
/// Return true if this chain starts before Other.
bool startsBefore(Chain *Other) {
bool startsBefore(const Chain *Other) const {
return StartInstIdx < Other->StartInstIdx;
}
@ -442,10 +442,17 @@ bool AArch64A57FPLoadBalancing::colorChainSet(std::vector<Chain*> GV,
// chains that we cannot change before we look at those we can,
// so the parity counter is updated and we know what color we should
// change them to!
// Final tie-break with instruction order so pass output is stable (i.e. not
// dependent on malloc'd pointer values).
std::sort(GV.begin(), GV.end(), [](const Chain *G1, const Chain *G2) {
if (G1->size() != G2->size())
return G1->size() > G2->size();
if (G1->requiresFixup() != G2->requiresFixup())
return G1->requiresFixup() > G2->requiresFixup();
// Make sure startsBefore() produces a stable final order.
assert((G1 == G2 || (G1->startsBefore(G2) ^ G2->startsBefore(G1))) &&
"Starts before not total order!");
return G1->startsBefore(G2);
});
Color PreferredColor = Parity < 0 ? Color::Even : Color::Odd;