Recognize nested MIN-MAX operations.
Rationale:
Prior to this CL, select optimizer and instruction
simplifier were unable to deal with more than one
select. This CLs improves MIN-MAX recognition by
allowing select diamonds to nest deeper and by
recognizing constant clipping operations. This
yields better optimizable code, as shown with
more saturation idioms.
Bug: b/74026074
Test: test-art-host,target
Change-Id: I8a616a19475f1ae87c2b5210afc76b14265bd571
diff --git a/compiler/optimizing/select_generator.cc b/compiler/optimizing/select_generator.cc
index 66e5142..3f52bdd 100644
--- a/compiler/optimizing/select_generator.cc
+++ b/compiler/optimizing/select_generator.cc
@@ -43,12 +43,16 @@
for (HInstructionIterator it(block->GetInstructions()); !it.Done(); it.Advance()) {
HInstruction* instruction = it.Current();
if (instruction->IsControlFlow()) {
- if (num_instructions > kMaxInstructionsInBranch) {
- return false;
- }
return instruction->IsGoto() || instruction->IsReturn();
} else if (instruction->CanBeMoved() && !instruction->HasSideEffects()) {
- num_instructions++;
+ if (instruction->IsSelect() &&
+ instruction->AsSelect()->GetCondition()->GetBlock() == block) {
+ // Count one HCondition and HSelect in the same block as a single instruction.
+ // This enables finding nested selects.
+ continue;
+ } else if (++num_instructions > kMaxInstructionsInBranch) {
+ return false; // bail as soon as we exceed number of allowed instructions
+ }
} else {
return false;
}
@@ -97,6 +101,7 @@
HBasicBlock* true_block = if_instruction->IfTrueSuccessor();
HBasicBlock* false_block = if_instruction->IfFalseSuccessor();
DCHECK_NE(true_block, false_block);
+
if (!IsSimpleBlock(true_block) ||
!IsSimpleBlock(false_block) ||
!BlocksMergeTogether(true_block, false_block)) {
@@ -107,10 +112,10 @@
// If the branches are not empty, move instructions in front of the If.
// TODO(dbrazdil): This puts an instruction between If and its condition.
// Implement moving of conditions to first users if possible.
- if (!true_block->IsSingleGoto() && !true_block->IsSingleReturn()) {
+ while (!true_block->IsSingleGoto() && !true_block->IsSingleReturn()) {
true_block->GetFirstInstruction()->MoveBefore(if_instruction);
}
- if (!false_block->IsSingleGoto() && !false_block->IsSingleReturn()) {
+ while (!false_block->IsSingleGoto() && !false_block->IsSingleReturn()) {
false_block->GetFirstInstruction()->MoveBefore(if_instruction);
}
DCHECK(true_block->IsSingleGoto() || true_block->IsSingleReturn());