[turbofan] Avoid some redundant checks of unordered comparison on arm/arm64.

R=bmeurer@chromium.org

Review URL: https://codereview.chromium.org/793303002

Cr-Commit-Position: refs/heads/master@{#25775}

src/compiler/arm/code-generator-arm.cc

@@ -693,8 +693,8 @@ void CodeGenerator::AssembleArchBranch(Instruction* instr, BranchInfo* branch) {
       __ b(eq, tlabel);
       break;
     case kUnorderedNotEqual:
-      __ b(vs, tlabel);
-    // Fall through.
+      // Unordered or not equal can be tested with "ne" condtion.
+      // See ARMv7 manual A8.3 - Conditional execution.
     case kNotEqual:
       __ b(ne, tlabel);
       break;
@@ -717,8 +717,8 @@ void CodeGenerator::AssembleArchBranch(Instruction* instr, BranchInfo* branch) {
       __ b(lo, tlabel);
       break;
     case kUnorderedGreaterThanOrEqual:
-      __ b(vs, tlabel);
-    // Fall through.
+      // Unordered, greater than or equal can be tested with "hs" condtion.
+      // See ARMv7 manual A8.3 - Conditional execution.
     case kUnsignedGreaterThanOrEqual:
       __ b(hs, tlabel);
       break;
@@ -729,8 +729,8 @@ void CodeGenerator::AssembleArchBranch(Instruction* instr, BranchInfo* branch) {
       __ b(ls, tlabel);
       break;
     case kUnorderedGreaterThan:
-      __ b(vs, tlabel);
-    // Fall through.
+      // Unordered or greater than can be tested with "hi" condtion.
+      // See ARMv7 manual A8.3 - Conditional execution.
     case kUnsignedGreaterThan:
       __ b(hi, tlabel);
       break;

src/compiler/arm64/code-generator-arm64.cc

@@ -787,8 +787,8 @@ void CodeGenerator::AssembleArchBranch(Instruction* instr, BranchInfo* branch) {
         __ B(eq, tlabel);
         break;
       case kUnorderedNotEqual:
-        __ B(vs, tlabel);
-      // Fall through.
+        // Unordered or not equal can be tested with "ne" condtion.
+        // See ARMv8 manual C1.2.3 - Condition Code.
       case kNotEqual:
         __ B(ne, tlabel);
         break;
@@ -811,8 +811,8 @@ void CodeGenerator::AssembleArchBranch(Instruction* instr, BranchInfo* branch) {
         __ B(lo, tlabel);
         break;
       case kUnorderedGreaterThanOrEqual:
-        __ B(vs, tlabel);
-      // Fall through.
+        // Unordered, greater than or equal can be tested with "hs" condtion.
+        // See ARMv8 manual C1.2.3 - Condition Code.
       case kUnsignedGreaterThanOrEqual:
         __ B(hs, tlabel);
         break;
@@ -823,8 +823,8 @@ void CodeGenerator::AssembleArchBranch(Instruction* instr, BranchInfo* branch) {
         __ B(ls, tlabel);
         break;
       case kUnorderedGreaterThan:
-        __ B(vs, tlabel);
-      // Fall through.
+        // Unordered or greater than can be tested with "hi" condtion.
+        // See ARMv8 manual C1.2.3 - Condition Code.
       case kUnsignedGreaterThan:
         __ B(hi, tlabel);
         break;