RFC: Generate select instruction for conditional returns.
The select generator currently only inserts select instructions
if there is a diamond shape with a phi.
This change extends the select generator to also deal with the
pattern:
if (condition) {
movable instruction 0
return value0
} else {
movable instruction 1
return value1
}
which it turns into:
moveable instruction 0
moveable instruction 1
return select (value0, value1, condition)
Test: 592-checker-regression-bool-input
Change-Id: Iac50fb181dc2c9b7619f28977298662bc09fc0e1
diff --git a/compiler/optimizing/select_generator.h b/compiler/optimizing/select_generator.h
index c6dca58..c060146 100644
--- a/compiler/optimizing/select_generator.h
+++ b/compiler/optimizing/select_generator.h
@@ -18,7 +18,7 @@
* This optimization recognizes the common diamond selection pattern and
* replaces it with an instance of the HSelect instruction.
*
- * Recognized pattern:
+ * Recognized patterns:
*
* If [ Condition ]
* / \
@@ -26,14 +26,30 @@
* \ /
* Phi [FalseValue, TrueValue]
*
+ * and
+ *
+ * If [ Condition ]
+ * / \
+ * false branch true branch
+ * return FalseValue return TrueValue
+ *
* The pattern will be simplified if `true_branch` and `false_branch` each
* contain at most one instruction without any side effects.
*
- * Blocks are merged into one and Select replaces the If and the Phi:
+ * Blocks are merged into one and Select replaces the If and the Phi.
+ *
+ * For the first pattern it simplifies to:
+ *
* true branch
* false branch
* Select [FalseValue, TrueValue, Condition]
*
+ * For the second pattern it simplifies to:
+ *
+ * true branch
+ * false branch
+ * return Select [FalseValue, TrueValue, Condition]
+ *
* Note: In order to recognize no side-effect blocks, this optimization must be
* run after the instruction simplifier has removed redundant suspend checks.
*/
@@ -42,19 +58,22 @@
#define ART_COMPILER_OPTIMIZING_SELECT_GENERATOR_H_
#include "optimization.h"
+#include "reference_type_propagation.h"
namespace art {
class HSelectGenerator : public HOptimization {
public:
- HSelectGenerator(HGraph* graph, OptimizingCompilerStats* stats)
- : HOptimization(graph, kSelectGeneratorPassName, stats) {}
+ HSelectGenerator(HGraph* graph,
+ VariableSizedHandleScope* handles,
+ OptimizingCompilerStats* stats);
void Run() OVERRIDE;
static constexpr const char* kSelectGeneratorPassName = "select_generator";
private:
+ VariableSizedHandleScope* handle_scope_;
DISALLOW_COPY_AND_ASSIGN(HSelectGenerator);
};