Merge "On x86 modified the generated instructions for case "divide by 2". As we can use fewer instructions to represent HDiv when divide by2."

2 files changed, 33 insertions, 8 deletions

diff --git a/compiler/optimizing/code_generator_x86_64.cc b/compiler/optimizing/code_generator_x86_64.cc
index 14cff05f58..e7212cd479 100644
--- a/compiler/optimizing/code_generator_x86_64.cc
+++ b/compiler/optimizing/code_generator_x86_64.cc
@@ -3608,9 +3608,17 @@ void InstructionCodeGeneratorX86_64::DivByPowerOfTwo(HDiv* instruction) {
   CpuRegister tmp = locations->GetTemp(0).AsRegister<CpuRegister>();
 
   if (instruction->GetResultType() == DataType::Type::kInt32) {
-    __ leal(tmp, Address(numerator, abs_imm - 1));
-    __ testl(numerator, numerator);
-    __ cmov(kGreaterEqual, tmp, numerator);
+    // When denominator is equal to 2, we can add signed bit and numerator to tmp.
+    // Below we are using addl instruction instead of cmov which give us 1 cycle benefit.
+    if (abs_imm == 2) {
+      __ leal(tmp, Address(numerator, 0));
+      __ shrl(tmp, Immediate(31));
+      __ addl(tmp, numerator);
+    } else {
+      __ leal(tmp, Address(numerator, abs_imm - 1));
+      __ testl(numerator, numerator);
+      __ cmov(kGreaterEqual, tmp, numerator);
+    }
     int shift = CTZ(imm);
     __ sarl(tmp, Immediate(shift));
 
@@ -3622,11 +3630,16 @@ void InstructionCodeGeneratorX86_64::DivByPowerOfTwo(HDiv* instruction) {
   } else {
     DCHECK_EQ(instruction->GetResultType(), DataType::Type::kInt64);
     CpuRegister rdx = locations->GetTemp(0).AsRegister<CpuRegister>();
-
-    codegen_->Load64BitValue(rdx, abs_imm - 1);
-    __ addq(rdx, numerator);
-    __ testq(numerator, numerator);
-    __ cmov(kGreaterEqual, rdx, numerator);
+    if (abs_imm == 2) {
+      __ movq(rdx, numerator);
+      __ shrq(rdx, Immediate(63));
+      __ addq(rdx, numerator);
+    } else {
+      codegen_->Load64BitValue(rdx, abs_imm - 1);
+      __ addq(rdx, numerator);
+      __ testq(numerator, numerator);
+      __ cmov(kGreaterEqual, rdx, numerator);
+    }
     int shift = CTZ(imm);
     __ sarq(rdx, Immediate(shift));
 
diff --git a/test/411-checker-hdiv-hrem-pow2/src/DivTest.java b/test/411-checker-hdiv-hrem-pow2/src/DivTest.java
index a3882e7c15..1a086ef04d 100644
--- a/test/411-checker-hdiv-hrem-pow2/src/DivTest.java
+++ b/test/411-checker-hdiv-hrem-pow2/src/DivTest.java
@@ -94,6 +94,9 @@ public class DivTest {
   /// CHECK-START-ARM64: java.lang.Integer DivTest.$noinline$IntDivBy2(int) disassembly (after)
   /// CHECK:                 add w{{\d+}}, w{{\d+}}, w{{\d+}}, lsr #31
   /// CHECK:                 asr w{{\d+}}, w{{\d+}}, #1
+  /// CHECK-START-X86_64: java.lang.Integer DivTest.$noinline$IntDivBy2(int) disassembly (after)
+  /// CHECK-NOT:             cmovnl/geq
+  /// CHECK:                 add
   private static Integer $noinline$IntDivBy2(int v) {
     int r = v / 2;
     return r;
@@ -102,6 +105,9 @@ public class DivTest {
   /// CHECK-START-ARM64: java.lang.Integer DivTest.$noinline$IntDivByMinus2(int) disassembly (after)
   /// CHECK:                 add w{{\d+}}, w{{\d+}}, w{{\d+}}, lsr #31
   /// CHECK:                 neg w{{\d+}}, w{{\d+}}, asr #1
+  /// CHECK-START-X86_64: java.lang.Integer DivTest.$noinline$IntDivByMinus2(int) disassembly (after)
+  /// CHECK-NOT:             cmovnl/geq
+  /// CHECK:                 add
   private static Integer $noinline$IntDivByMinus2(int v) {
     int r = v / -2;
     return r;
@@ -205,6 +211,9 @@ public class DivTest {
   /// CHECK-START-ARM64: java.lang.Long DivTest.$noinline$LongDivBy2(long) disassembly (after)
   /// CHECK:                 add x{{\d+}}, x{{\d+}}, x{{\d+}}, lsr #63
   /// CHECK:                 asr x{{\d+}}, x{{\d+}}, #1
+  /// CHECK-START-X86_64: java.lang.Long DivTest.$noinline$LongDivBy2(long) disassembly (after)
+  /// CHECK-NOT:             cmovnl/geq
+  /// CHECK:                 addq
   private static Long $noinline$LongDivBy2(long v) {
     long r = v / 2;
     return r;
@@ -213,6 +222,9 @@ public class DivTest {
   /// CHECK-START-ARM64: java.lang.Long DivTest.$noinline$LongDivByMinus2(long) disassembly (after)
   /// CHECK:                 add x{{\d+}}, x{{\d+}}, x{{\d+}}, lsr #63
   /// CHECK:                 neg x{{\d+}}, x{{\d+}}, asr #1
+  /// CHECK-START-X86_64: java.lang.Long DivTest.$noinline$LongDivByMinus2(long) disassembly (after)
+  /// CHECK-NOT:             cmovnl/geq
+  /// CHECK:                 addq
   private static Long $noinline$LongDivByMinus2(long v) {
     long r = v / -2;
     return r;