Better handling of zero in compare and branch for MIPS.

runtime/vm/assembler_mips.h

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef VM_ASSEMBLER_MIPS_H_
 #define VM_ASSEMBLER_MIPS_H_
 
 #ifndef VM_ASSEMBLER_H_
 #error Do not include assembler_mips.h directly; use assembler.h instead.
 #endif
@@ skipping 841 matching lines @@
       LoadImmediate(TMP1, value);
       addu(rd, rs, TMP1);
     }
   }
 
   void AddImmediate(Register rd, int32_t value) {
     AddImmediate(rd, rd, value);
   }
 
   void BranchEqual(Register rd, int32_t value, Label* l) {
-    ASSERT(rd != CMPRES2);
-    LoadImmediate(CMPRES2, value);
-    beq(rd, CMPRES2, l);
+    if (value == 0) {
+      beq(rd, ZR, l);
+    } else {
+      ASSERT(rd != CMPRES2);
+      LoadImmediate(CMPRES2, value);
+      beq(rd, CMPRES2, l);
+    }
   }
 
   void BranchEqual(Register rd, const Object& object, Label* l) {
     ASSERT(rd != CMPRES2);
     LoadObject(CMPRES2, object);
     beq(rd, CMPRES2, l);
   }
 
   void BranchNotEqual(Register rd, int32_t value, Label* l) {
-    ASSERT(rd != CMPRES2);
-    LoadImmediate(CMPRES2, value);
-    bne(rd, CMPRES2, l);
+    if (value == 0) {
+      bne(rd, ZR, l);
+    } else {
+      ASSERT(rd != CMPRES2);
+      LoadImmediate(CMPRES2, value);
+      bne(rd, CMPRES2, l);
+    }
   }
 
   void BranchNotEqual(Register rd, const Object& object, Label* l) {
     ASSERT(rd != CMPRES2);
     LoadObject(CMPRES2, object);
     bne(rd, CMPRES2, l);
   }
 
   void BranchSignedGreater(Register rd, Register rs, Label* l) {
     slt(CMPRES2, rs, rd);  // CMPRES2 = rd > rs ? 1 : 0.
     bne(CMPRES2, ZR, l);
   }
 
   void BranchSignedGreater(Register rd, int32_t value, Label* l) {
-    ASSERT(rd != CMPRES2);
-    LoadImmediate(CMPRES2, value);
-    BranchSignedGreater(rd, CMPRES2, l);
+    if (value == 0) {
+      bgtz(rd, l);
+    } else {
+      ASSERT(rd != CMPRES2);
+      LoadImmediate(CMPRES2, value);
+      BranchSignedGreater(rd, CMPRES2, l);
+    }
   }
 
   void BranchUnsignedGreater(Register rd, Register rs, Label* l) {
     sltu(CMPRES2, rs, rd);
     bne(CMPRES2, ZR, l);
   }
 
   void BranchUnsignedGreater(Register rd, int32_t value, Label* l) {
-    ASSERT(rd != CMPRES2);
-    LoadImmediate(CMPRES2, value);
-    BranchUnsignedGreater(rd, CMPRES2, l);
+    if (value == 0) {
+      BranchNotEqual(rd, 0, l);
+    } else {
+      ASSERT(rd != CMPRES2);
+      LoadImmediate(CMPRES2, value);
+      BranchUnsignedGreater(rd, CMPRES2, l);
+    }
   }
 
   void BranchSignedGreaterEqual(Register rd, Register rs, Label* l) {
     slt(CMPRES2, rd, rs);  // CMPRES2 = rd < rs ? 1 : 0.
     beq(CMPRES2, ZR, l);  // If CMPRES2 = 0, then rd >= rs.
   }
 
   void BranchSignedGreaterEqual(Register rd, int32_t value, Label* l) {
-    if (Utils::IsInt(kImmBits, value)) {
-      slti(CMPRES2, rd, Immediate(value));
-      beq(CMPRES2, ZR, l);
+    if (value == 0) {
+      bgez(rd, l);
     } else {
-      ASSERT(rd != CMPRES2);
-      LoadImmediate(CMPRES2, value);
-      BranchSignedGreaterEqual(rd, CMPRES2, l);
+      if (Utils::IsInt(kImmBits, value)) {
+        slti(CMPRES2, rd, Immediate(value));
+        beq(CMPRES2, ZR, l);
+      } else {
+        ASSERT(rd != CMPRES2);
+        LoadImmediate(CMPRES2, value);
+        BranchSignedGreaterEqual(rd, CMPRES2, l);
+      }
     }
   }
 
   void BranchUnsignedGreaterEqual(Register rd, Register rs, Label* l) {
     sltu(CMPRES2, rd, rs);  // CMPRES2 = rd < rs ? 1 : 0.
     beq(CMPRES2, ZR, l);
   }
 
   void BranchUnsignedGreaterEqual(Register rd, int32_t value, Label* l) {
-    if (Utils::IsUint(kImmBits, value)) {
-      sltiu(CMPRES2, rd, Immediate(value));
-      beq(CMPRES2, ZR, l);
+    if (value == 0) {
+      b(l);
     } else {
-      ASSERT(rd != CMPRES2);
-      LoadImmediate(CMPRES2, value);
-      BranchUnsignedGreaterEqual(rd, CMPRES2, l);
+      if (Utils::IsUint(kImmBits, value)) {
+        sltiu(CMPRES2, rd, Immediate(value));
+        beq(CMPRES2, ZR, l);
+      } else {
+        ASSERT(rd != CMPRES2);
+        LoadImmediate(CMPRES2, value);
+        BranchUnsignedGreaterEqual(rd, CMPRES2, l);
+      }
     }
   }
 
   void BranchSignedLess(Register rd, Register rs, Label* l) {
     BranchSignedGreater(rs, rd, l);
   }
 
   void BranchSignedLess(Register rd, int32_t value, Label* l) {
-    if (Utils::IsInt(kImmBits, value)) {
-      slti(CMPRES2, rd, Immediate(value));
-      bne(CMPRES2, ZR, l);
+    if (value == 0) {
+      bltz(rd, l);
     } else {
-      ASSERT(rd != CMPRES2);
-      LoadImmediate(CMPRES2, value);
-      BranchSignedGreater(CMPRES2, rd, l);
+      if (Utils::IsInt(kImmBits, value)) {
+        slti(CMPRES2, rd, Immediate(value));
+        bne(CMPRES2, ZR, l);
+      } else {
+        ASSERT(rd != CMPRES2);
+        LoadImmediate(CMPRES2, value);
+        BranchSignedGreater(CMPRES2, rd, l);
+      }
     }
   }
 
   void BranchUnsignedLess(Register rd, Register rs, Label* l) {
     BranchUnsignedGreater(rs, rd, l);
   }
 
   void BranchUnsignedLess(Register rd, int32_t value, Label* l) {
+    ASSERT(value != 0);
     if (Utils::IsUint(kImmBits, value)) {
       sltiu(CMPRES2, rd, Immediate(value));
       bne(CMPRES2, ZR, l);
     } else {
       ASSERT(rd != CMPRES2);
       LoadImmediate(CMPRES2, value);
       BranchUnsignedGreater(CMPRES2, rd, l);
     }
   }
 
   void BranchSignedLessEqual(Register rd, Register rs, Label* l) {
     BranchSignedGreaterEqual(rs, rd, l);
   }
 
   void BranchSignedLessEqual(Register rd, int32_t value, Label* l) {
-    ASSERT(rd != CMPRES2);
-    LoadImmediate(CMPRES2, value);
-    BranchSignedGreaterEqual(CMPRES2, rd, l);
+    if (value == 0) {
+      blez(rd, l);
+    } else {
+      ASSERT(rd != CMPRES2);
+      LoadImmediate(CMPRES2, value);
+      BranchSignedGreaterEqual(CMPRES2, rd, l);
+    }
   }
 
   void BranchUnsignedLessEqual(Register rd, Register rs, Label* l) {
     BranchUnsignedGreaterEqual(rs, rd, l);
   }
 
   void BranchUnsignedLessEqual(Register rd, int32_t value, Label* l) {
     ASSERT(rd != CMPRES2);
     LoadImmediate(CMPRES2, value);
     BranchUnsignedGreaterEqual(CMPRES2, rd, l);
@@ skipping 235 matching lines @@
                                   Register value,
                                   Label* no_update);
 
   DISALLOW_ALLOCATION();
   DISALLOW_COPY_AND_ASSIGN(Assembler);
 };
 
 }  // namespace dart
 
 #endif  // VM_ASSEMBLER_MIPS_H_