Find better split positions in the register allocator.
In a standard if/else control flow graph, this avoids
doing a move in one branch if the other branch decided
to move an interval.
This also needs a new register hint kind, which is what
was the location of the interval at the predecessor block.
Change-Id: I18b78264587b4d693540fbb5e014d12df2add3e2
diff --git a/compiler/optimizing/ssa_liveness_analysis.h b/compiler/optimizing/ssa_liveness_analysis.h
index b74e655..7b98c4e 100644
--- a/compiler/optimizing/ssa_liveness_analysis.h
+++ b/compiler/optimizing/ssa_liveness_analysis.h
@@ -23,6 +23,7 @@
namespace art {
class CodeGenerator;
+class SsaLivenessAnalysis;
static constexpr int kNoRegister = -1;
@@ -690,7 +691,7 @@
// Returns the first register hint that is at least free before
// the value contained in `free_until`. If none is found, returns
// `kNoRegister`.
- int FindFirstRegisterHint(size_t* free_until) const;
+ int FindFirstRegisterHint(size_t* free_until, const SsaLivenessAnalysis& liveness) const;
// If there is enough at the definition site to find a register (for example
// it uses the same input as the first input), returns the register as a hint.
@@ -1116,14 +1117,18 @@
}
HBasicBlock* GetBlockFromPosition(size_t index) const {
- HInstruction* instruction = GetInstructionFromPosition(index / 2);
+ HInstruction* instruction = GetInstructionFromPosition(index);
if (instruction == nullptr) {
// If we are at a block boundary, get the block following.
- instruction = GetInstructionFromPosition((index / 2) + 1);
+ instruction = GetInstructionFromPosition(index + 1);
}
return instruction->GetBlock();
}
+ bool IsAtBlockBoundary(size_t index) const {
+ return GetInstructionFromPosition(index) == nullptr;
+ }
+
HInstruction* GetTempUser(LiveInterval* temp) const {
// A temporary shares the same lifetime start as the instruction that requires it.
DCHECK(temp->IsTemp());