From 81425a20b2c2aeb28a54fd95bb47569001ae70bf Mon Sep 17 00:00:00 2001
From: "olivf@chromium.org"
 <olivf@chromium.org@ce2b1a6d-e550-0410-aec6-3dcde31c8c00>
Date: Fri, 13 Sep 2013 12:01:32 +0000
Subject: [PATCH] Intel: Branch reordering and port arm EmitNumberUntagD()
 Improvement

R=bmeurer@chromium.org

Review URL: https://codereview.chromium.org/23872026

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@16714 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
---
 src/ia32/lithium-codegen-ia32.cc | 34 ++++++++++++++++++----------------
 src/x64/lithium-codegen-x64.cc   | 38 +++++++++++++++++++++-----------------
 2 files changed, 39 insertions(+), 33 deletions(-)

diff --git a/src/ia32/lithium-codegen-ia32.cc b/src/ia32/lithium-codegen-ia32.cc
index 9727b84..7d7b51d 100644
--- a/src/ia32/lithium-codegen-ia32.cc
+++ b/src/ia32/lithium-codegen-ia32.cc
@@ -5308,7 +5308,7 @@ void LCodeGen::EmitNumberUntagD(Register input_reg,
                                 bool deoptimize_on_minus_zero,
                                 LEnvironment* env,
                                 NumberUntagDMode mode) {
-  Label load_smi, done;
+  Label convert, load_smi, done;
 
   if (mode == NUMBER_CANDIDATE_IS_ANY_TAGGED) {
     // Smi check.
@@ -5317,26 +5317,15 @@ void LCodeGen::EmitNumberUntagD(Register input_reg,
     // Heap number map check.
     __ cmp(FieldOperand(input_reg, HeapObject::kMapOffset),
            factory()->heap_number_map());
-    if (!can_convert_undefined_to_nan) {
-      DeoptimizeIf(not_equal, env);
+    if (can_convert_undefined_to_nan) {
+      __ j(not_equal, &convert, Label::kNear);
     } else {
-      Label heap_number, convert;
-      __ j(equal, &heap_number, Label::kNear);
-
-      // Convert undefined (and hole) to NaN.
-      __ cmp(input_reg, factory()->undefined_value());
       DeoptimizeIf(not_equal, env);
-
-      __ bind(&convert);
-      ExternalReference nan =
-          ExternalReference::address_of_canonical_non_hole_nan();
-      __ movdbl(result_reg, Operand::StaticVariable(nan));
-      __ jmp(&done, Label::kNear);
-
-      __ bind(&heap_number);
     }
+
     // Heap number to XMM conversion.
     __ movdbl(result_reg, FieldOperand(input_reg, HeapNumber::kValueOffset));
+
     if (deoptimize_on_minus_zero) {
       XMMRegister xmm_scratch = xmm0;
       __ xorps(xmm_scratch, xmm_scratch);
@@ -5347,6 +5336,19 @@ void LCodeGen::EmitNumberUntagD(Register input_reg,
       DeoptimizeIf(not_zero, env);
     }
     __ jmp(&done, Label::kNear);
+
+    if (can_convert_undefined_to_nan) {
+      __ bind(&convert);
+
+      // Convert undefined (and hole) to NaN.
+      __ cmp(input_reg, factory()->undefined_value());
+      DeoptimizeIf(not_equal, env);
+
+      ExternalReference nan =
+          ExternalReference::address_of_canonical_non_hole_nan();
+      __ movdbl(result_reg, Operand::StaticVariable(nan));
+      __ jmp(&done, Label::kNear);
+    }
   } else {
     ASSERT(mode == NUMBER_CANDIDATE_IS_SMI);
   }
diff --git a/src/x64/lithium-codegen-x64.cc b/src/x64/lithium-codegen-x64.cc
index a02a88e..6f4d3e3 100644
--- a/src/x64/lithium-codegen-x64.cc
+++ b/src/x64/lithium-codegen-x64.cc
@@ -4623,7 +4623,7 @@ void LCodeGen::EmitNumberUntagD(Register input_reg,
                                 bool deoptimize_on_minus_zero,
                                 LEnvironment* env,
                                 NumberUntagDMode mode) {
-  Label load_smi, done;
+  Label convert, load_smi, done;
 
   if (mode == NUMBER_CANDIDATE_IS_ANY_TAGGED) {
     // Smi check.
@@ -4632,25 +4632,17 @@ void LCodeGen::EmitNumberUntagD(Register input_reg,
     // Heap number map check.
     __ CompareRoot(FieldOperand(input_reg, HeapObject::kMapOffset),
                    Heap::kHeapNumberMapRootIndex);
-    if (!can_convert_undefined_to_nan) {
-      DeoptimizeIf(not_equal, env);
-    } else {
-      Label heap_number, convert;
-      __ j(equal, &heap_number, Label::kNear);
 
-      // Convert undefined (and hole) to NaN. Compute NaN as 0/0.
-      __ CompareRoot(input_reg, Heap::kUndefinedValueRootIndex);
-      DeoptimizeIf(not_equal, env);
-
-      __ bind(&convert);
-      __ xorps(result_reg, result_reg);
-      __ divsd(result_reg, result_reg);
-      __ jmp(&done, Label::kNear);
+    // On x64 it is safe to load at heap number offset before evaluating the map
+    // check, since all heap objects are at least two words long.
+    __ movsd(result_reg, FieldOperand(input_reg, HeapNumber::kValueOffset));
 
-      __ bind(&heap_number);
+    if (can_convert_undefined_to_nan) {
+      __ j(not_equal, &convert);
+    } else {
+      DeoptimizeIf(not_equal, env);
     }
-    // Heap number to XMM conversion.
-    __ movsd(result_reg, FieldOperand(input_reg, HeapNumber::kValueOffset));
+
     if (deoptimize_on_minus_zero) {
       XMMRegister xmm_scratch = xmm0;
       __ xorps(xmm_scratch, xmm_scratch);
@@ -4661,6 +4653,18 @@ void LCodeGen::EmitNumberUntagD(Register input_reg,
       DeoptimizeIf(not_zero, env);
     }
     __ jmp(&done, Label::kNear);
+
+    if (can_convert_undefined_to_nan) {
+      __ bind(&convert);
+
+      // Convert undefined (and hole) to NaN. Compute NaN as 0/0.
+      __ CompareRoot(input_reg, Heap::kUndefinedValueRootIndex);
+      DeoptimizeIf(not_equal, env);
+
+      __ xorps(result_reg, result_reg);
+      __ divsd(result_reg, result_reg);
+      __ jmp(&done, Label::kNear);
+    }
   } else {
     ASSERT(mode == NUMBER_CANDIDATE_IS_SMI);
   }
-- 
2.7.4