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[gcmole] Fixes for unreachable code

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Enforce the invariant that unreachable implicates an empty live set and
fix the implementation of |= and &= operator.
This is a fix-up for http://crrev.com/2694103005.

R=vegorov@chromium.org
CC=mstarzinger@chromium.org, machenbach@chromium.org
BUG=v8:5970

Review-Url: https://codereview.chromium.org/2691103008
Cr-Commit-Position: refs/heads/master@{#43251}
This commit is contained in:
clemensh 2017-02-16 06:13:11 -08:00 committed by Commit bot
parent e2b83fbbfd
commit 4b0edcf7e0
1 changed files with 20 additions and 9 deletions
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29
tools/gcmole/gcmole.cc
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@ -348,7 +348,7 @@ class Environment {
}
bool Equal(const Environment& env) {
if (unreachable_) return env.unreachable_;
if (unreachable_ && env.unreachable_) return true;
size_t size = std::max(live_.size(), env.live_.size());
for (size_t i = 0; i < size; ++i) {
if (is_live(i) != env.is_live(i)) return false;
@ -405,7 +405,8 @@ class Environment {
}
void set_live(size_t pos) {
if (live_.size() <= pos) live_.resize(std::max(pos + 1, 2 * live_.size()));
if (unreachable_) return;
if (pos >= live_.size()) live_.resize(pos + 1);
live_[pos] = true;
}
@ -414,19 +415,27 @@ class Environment {
}
Environment& operator|=(const Environment& o) {
unreachable_ |= o.unreachable_;
for (size_t i = 0, e = o.live_.size(); i < e; ++i) {
if (o.live_[i]) set_live(i);
if (o.unreachable_) {
unreachable_ = true;
live_.clear();
} else if (!unreachable_) {
for (size_t i = 0, e = o.live_.size(); i < e; ++i) {
if (o.live_[i]) set_live(i);
}
}
return *this;
}
Environment& operator&=(const Environment& o) {
unreachable_ &= o.unreachable_;
size_t size = std::min(live_.size(), o.live_.size());
if (live_.size() > size) live_.resize(size);
if (o.unreachable_) return *this;
if (unreachable_) return *this = o;
// Carry over false bits from the tail of o.live_, and reset all bits that
// are not set in o.live_.
size_t size = std::max(live_.size(), o.live_.size());
if (size > live_.size()) live_.resize(size);
for (size_t i = 0; i < size; ++i) {
if (live_[i] && (i > o.live_.size() || !o.live_[i])) live_[i] = false;
if (live_[i] && (i >= o.live_.size() || !o.live_[i])) live_[i] = false;
}
return *this;
}
@ -435,6 +444,8 @@ class Environment {
static std::vector<Environment*> envs_;
std::vector<bool> live_;
// unreachable_ == true implies live_.empty(), but still is_live(i) returns
// true for all i.
bool unreachable_ = false;
friend class ExprEffect;