Fix conditional jump over jmp (X86/X86-64/ARM32)
Optimize the code generation for 'if' statements to jump to the
'false' block if the next block to be generated is the 'true' block.
Add an X86-64 test for this case.
Note that ARM64 & MIPS64 have not been updated.
Change-Id: Iebb1352feb9d3bd0142d8b0621a2e3069a708ea7
Signed-off-by: Mark Mendell <mark.p.mendell@intel.com>
diff --git a/compiler/optimizing/code_generator_arm.cc b/compiler/optimizing/code_generator_arm.cc
index 3dc3b7f..6d05293 100644
--- a/compiler/optimizing/code_generator_arm.cc
+++ b/compiler/optimizing/code_generator_arm.cc
@@ -1300,20 +1300,29 @@
DCHECK_EQ(cond_value, 0);
}
} else {
- if (!cond->IsCondition() || cond->AsCondition()->NeedsMaterialization()) {
- // Condition has been materialized, compare the output to 0
+ // Can we optimize the jump if we know that the next block is the true case?
+ HCondition* condition = cond->AsCondition();
+ bool can_jump_to_false = CanReverseCondition(always_true_target, false_target, condition);
+ if (condition == nullptr || condition->NeedsMaterialization()) {
+ // Condition has been materialized, compare the output to 0.
DCHECK(instruction->GetLocations()->InAt(0).IsRegister());
+ if (can_jump_to_false) {
+ __ CompareAndBranchIfZero(instruction->GetLocations()->InAt(0).AsRegister<Register>(),
+ false_target);
+ return;
+ }
__ CompareAndBranchIfNonZero(instruction->GetLocations()->InAt(0).AsRegister<Register>(),
true_target);
} else {
// Condition has not been materialized, use its inputs as the
// comparison and its condition as the branch condition.
- Primitive::Type type =
- cond->IsCondition() ? cond->InputAt(0)->GetType() : Primitive::kPrimInt;
+ Primitive::Type type = (condition != nullptr)
+ ? cond->InputAt(0)->GetType()
+ : Primitive::kPrimInt;
// Is this a long or FP comparison that has been folded into the HCondition?
if (type == Primitive::kPrimLong || Primitive::IsFloatingPointType(type)) {
// Generate the comparison directly.
- GenerateCompareTestAndBranch(instruction->AsIf(), cond->AsCondition(),
+ GenerateCompareTestAndBranch(instruction->AsIf(), condition,
true_target, false_target, always_true_target);
return;
}
@@ -1328,7 +1337,12 @@
DCHECK(right.IsConstant());
GenerateCompareWithImmediate(left, CodeGenerator::GetInt32ValueOf(right.GetConstant()));
}
- __ b(true_target, ARMCondition(cond->AsCondition()->GetCondition()));
+ if (can_jump_to_false) {
+ __ b(false_target, ARMCondition(condition->GetOppositeCondition()));
+ return;
+ }
+
+ __ b(true_target, ARMCondition(condition->GetCondition()));
}
}
if (false_target != nullptr) {