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Speed up the inner loop of free register allocation.

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Review URL: http://codereview.chromium.org/42296

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@1528 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
This commit is contained in:
whesse@chromium.org 2009-03-18 10:31:31 +00:00
parent 22f9dbf651
commit 10be4f7ffd
2 changed files with 17 additions and 8 deletions
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9
src/register-allocator.cc
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@ -83,11 +83,10 @@ void RegisterFile::CopyTo(RegisterFile* other) {
Result RegisterAllocator::AllocateWithoutSpilling() {
// Return the first free register, if any.
for (int i = 0; i < kNumRegisters; i++) {
if (!is_used(i)) {
Register free_reg = { i };
return Result(free_reg, cgen_);
}
int free_reg = registers_.ScanForFreeRegister();
if (free_reg < kNumRegisters) {
Register free_result = { free_reg };
return Result(free_result, cgen_);
}
return Result(cgen_);
}

16
src/register-allocator.h
View File

@ -149,10 +149,9 @@ class RegisterFile BASE_EMBEDDED {
// Record that a register will no longer be used by decrementing its
// reference count.
void Unuse(Register reg) {
ASSERT(!reg.is(no_reg));
ASSERT(is_used(reg.code()));
if (is_used(reg.code())) {
ref_counts_[reg.code()]--;
}
ref_counts_[reg.code()]--;
}
// Copy the reference counts from this register file to the other.
@ -161,6 +160,17 @@ class RegisterFile BASE_EMBEDDED {
private:
int ref_counts_[kNumRegisters];
// Very fast inlined loop to find a free register.
// Used in RegisterAllocator::AllocateWithoutSpilling.
// Returns kNumRegisters if no free register found.
inline int ScanForFreeRegister() {
int i = 0;
for (; i < kNumRegisters ; ++i) {
if (ref_counts_[i] == 0) break;
}
return i;
}
friend class RegisterAllocator;
};