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>

1 files changed, 16 insertions, 0 deletions

diff --git a/compiler/optimizing/code_generator_utils.cc b/compiler/optimizing/code_generator_utils.cc
index 921c1d86c2..bf354e7ee2 100644
--- a/compiler/optimizing/code_generator_utils.cc
+++ b/compiler/optimizing/code_generator_utils.cc
@@ -15,6 +15,7 @@
  */
 
 #include "code_generator_utils.h"
+#include "nodes.h"
 
 #include "base/logging.h"
 
@@ -94,4 +95,19 @@ void CalculateMagicAndShiftForDivRem(int64_t divisor, bool is_long,
   *shift = is_long ? p - 64 : p - 32;
 }
 
+// Is it valid to reverse the condition? Uses the values supplied to
+// GenerateTestAndBranch() in instruction generators.
+bool CanReverseCondition(Label* always_true_target,
+                         Label* false_target,
+                         HCondition* condition) {
+  // 'always_true_target' is null when the 'true' path is to the next
+  // block to be generated.  Check the type of the condition to ensure that
+  // FP conditions are not swapped.  This is for future fusing of HCompare and
+  // HCondition.
+  // Note:  If the condition is nullptr, then it is always okay to reverse.
+  return always_true_target == nullptr && false_target != nullptr &&
+         (condition == nullptr ||
+          !Primitive::IsFloatingPointType(condition->InputAt(0)->GetType()));
+}
+
 }  // namespace art