MIPS: Use BOVC/BNVC for overflow checking on r6.

src/mips/macro-assembler-mips.cc

 
 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <limits.h>  // For LONG_MIN, LONG_MAX.
 
 #if V8_TARGET_ARCH_MIPS
 
 #include "src/base/bits.h"
@@ skipping 4288 matching lines @@
 
 void MacroAssembler::SmiToDoubleFPURegister(Register smi,
                                             FPURegister value,
                                             Register scratch1) {
   sra(scratch1, smi, kSmiTagSize);
   mtc1(scratch1, value);
   cvt_d_w(value, value);
 }
 
 
-void MacroAssembler::AdduAndCheckForOverflow(Register dst, Register left,
-                                             const Operand& right,
-                                             Register overflow_dst,
-                                             Register scratch) {
+static inline void BranchOvfHelper(MacroAssembler* masm, Register overflow_dst,
+                                   Label* overflow_label,
+                                   Label* no_overflow_label) {
+  DCHECK(overflow_label || no_overflow_label);
+  if (!overflow_label) {
+    DCHECK(no_overflow_label);
+    masm->Branch(no_overflow_label, ge, overflow_dst, Operand(zero_reg));
+  } else {
+    masm->Branch(overflow_label, lt, overflow_dst, Operand(zero_reg));
+    if (no_overflow_label) masm->Branch(no_overflow_label);
+  }
+}
+
+
+void MacroAssembler::AddBranchOvf(Register dst, Register left,
+                                  const Operand& right, Label* overflow_label,
+                                  Label* no_overflow_label, Register scratch) {
   if (right.is_reg()) {
-    AdduAndCheckForOverflow(dst, left, right.rm(), overflow_dst, scratch);
+    AddBranchOvf(dst, left, right.rm(), overflow_label, no_overflow_label,
+                 scratch);
   } else {
-    if (dst.is(left)) {
-      mov(scratch, left);                   // Preserve left.
-      Addu(dst, left, right.immediate());   // Left is overwritten.
-      xor_(scratch, dst, scratch);          // Original left.
-      // Load right since xori takes uint16 as immediate.
-      Addu(t9, zero_reg, right);
-      xor_(overflow_dst, dst, t9);
-      and_(overflow_dst, overflow_dst, scratch);
+    if (IsMipsArchVariant(kMips32r6)) {
+      Register right_reg = t9;
+      DCHECK(!left.is(right_reg));
+      li(right_reg, Operand(right));
+      AddBranchOvf(dst, left, right_reg, overflow_label, no_overflow_label);
     } else {
-      Addu(dst, left, right.immediate());
-      xor_(overflow_dst, dst, left);
-      // Load right since xori takes uint16 as immediate.
-      Addu(t9, zero_reg, right);
-      xor_(scratch, dst, t9);
-      and_(overflow_dst, scratch, overflow_dst);
+      Register overflow_dst = t9;
+      DCHECK(!dst.is(scratch));
+      DCHECK(!dst.is(overflow_dst));
+      DCHECK(!scratch.is(overflow_dst));
+      DCHECK(!left.is(overflow_dst));
+      if (dst.is(left)) {
+        mov(scratch, left);                  // Preserve left.
+        Addu(dst, left, right.immediate());  // Left is overwritten.
+        xor_(scratch, dst, scratch);         // Original left.
+        // Load right since xori takes uint16 as immediate.
+        Addu(overflow_dst, zero_reg, right);
+        xor_(overflow_dst, dst, overflow_dst);
+        and_(overflow_dst, overflow_dst, scratch);
+      } else {
+        Addu(dst, left, right.immediate());
+        xor_(overflow_dst, dst, left);
+        // Load right since xori takes uint16 as immediate.
+        Addu(scratch, zero_reg, right);
+        xor_(scratch, dst, scratch);
+        and_(overflow_dst, scratch, overflow_dst);
+      }
+      BranchOvfHelper(this, overflow_dst, overflow_label, no_overflow_label);
     }
   }
 }
 
 
-void MacroAssembler::AdduAndCheckForOverflow(Register dst, Register left,
-                                             Register right,
-                                             Register overflow_dst,
-                                             Register scratch) {
-  DCHECK(!dst.is(overflow_dst));
-  DCHECK(!dst.is(scratch));
-  DCHECK(!overflow_dst.is(scratch));
-  DCHECK(!overflow_dst.is(left));
-  DCHECK(!overflow_dst.is(right));
+void MacroAssembler::AddBranchOvf(Register dst, Register left, Register right,
+                                  Label* overflow_label,
+                                  Label* no_overflow_label, Register scratch) {
+  if (IsMipsArchVariant(kMips32r6)) {
+    if (!overflow_label) {
+      DCHECK(no_overflow_label);
+      DCHECK(!dst.is(scratch));
+      Register left_reg = left.is(dst) ? scratch : left;
+      Register right_reg = right.is(dst) ? t9 : right;
+      DCHECK(!dst.is(left_reg));
+      DCHECK(!dst.is(right_reg));
+      Move(left_reg, left);
+      Move(right_reg, right);
+      addu(dst, left, right);
+      bnvc(left_reg, right_reg, no_overflow_label);
+    } else {
+      bovc(left, right, overflow_label);
+      addu(dst, left, right);
+      if (no_overflow_label) bc(no_overflow_label);
+    }
+  } else {
+    Register overflow_dst = t9;
+    DCHECK(!dst.is(scratch));
+    DCHECK(!dst.is(overflow_dst));
+    DCHECK(!scratch.is(overflow_dst));
+    DCHECK(!left.is(overflow_dst));
+    DCHECK(!right.is(overflow_dst));
+    DCHECK(!left.is(scratch));
+    DCHECK(!right.is(scratch));
 
-  if (left.is(right) && dst.is(left)) {
-    DCHECK(!dst.is(t9));
-    DCHECK(!scratch.is(t9));
-    DCHECK(!left.is(t9));
-    DCHECK(!right.is(t9));
-    DCHECK(!overflow_dst.is(t9));
-    mov(t9, right);
-    right = t9;
-  }
+    if (left.is(right) && dst.is(left)) {
+      mov(overflow_dst, right);
+      right = overflow_dst;
+    }
 
-  if (dst.is(left)) {
-    mov(scratch, left);  // Preserve left.
-    addu(dst, left, right);  // Left is overwritten.
-    xor_(scratch, dst, scratch);  // Original left.
-    xor_(overflow_dst, dst, right);
-    and_(overflow_dst, overflow_dst, scratch);
-  } else if (dst.is(right)) {
-    mov(scratch, right);  // Preserve right.
-    addu(dst, left, right);  // Right is overwritten.
-    xor_(scratch, dst, scratch);  // Original right.
-    xor_(overflow_dst, dst, left);
-    and_(overflow_dst, overflow_dst, scratch);
-  } else {
-    addu(dst, left, right);
-    xor_(overflow_dst, dst, left);
-    xor_(scratch, dst, right);
-    and_(overflow_dst, scratch, overflow_dst);
+    if (dst.is(left)) {
+      mov(scratch, left);           // Preserve left.
+      addu(dst, left, right);       // Left is overwritten.
+      xor_(scratch, dst, scratch);  // Original left.
+      xor_(overflow_dst, dst, right);
+      and_(overflow_dst, overflow_dst, scratch);
+    } else if (dst.is(right)) {
+      mov(scratch, right);          // Preserve right.
+      addu(dst, left, right);       // Right is overwritten.
+      xor_(scratch, dst, scratch);  // Original right.
+      xor_(overflow_dst, dst, left);
+      and_(overflow_dst, overflow_dst, scratch);
+    } else {
+      addu(dst, left, right);
+      xor_(overflow_dst, dst, left);
+      xor_(scratch, dst, right);
+      and_(overflow_dst, scratch, overflow_dst);
+    }
+    BranchOvfHelper(this, overflow_dst, overflow_label, no_overflow_label);
   }
 }
 
 
-void MacroAssembler::SubuAndCheckForOverflow(Register dst, Register left,
-                                             const Operand& right,
-                                             Register overflow_dst,
-                                             Register scratch) {
+void MacroAssembler::SubBranchOvf(Register dst, Register left,
+                                  const Operand& right, Label* overflow_label,
+                                  Label* no_overflow_label, Register scratch) {
+  DCHECK(overflow_label || no_overflow_label);
   if (right.is_reg()) {
-    SubuAndCheckForOverflow(dst, left, right.rm(), overflow_dst, scratch);
+    SubBranchOvf(dst, left, right.rm(), overflow_label, no_overflow_label,
+                 scratch);
   } else {
+    Register overflow_dst = t9;
+    DCHECK(!dst.is(scratch));
+    DCHECK(!dst.is(overflow_dst));
+    DCHECK(!scratch.is(overflow_dst));
+    DCHECK(!left.is(overflow_dst));
+    DCHECK(!left.is(scratch));
     if (dst.is(left)) {
       mov(scratch, left);                      // Preserve left.
-      Subu(dst, left, right);                  // Left is overwritten.
-      xor_(overflow_dst, dst, scratch);        // scratch is original left.
+      Subu(dst, left, right.immediate());      // Left is overwritten.
       // Load right since xori takes uint16 as immediate.
-      Addu(t9, zero_reg, right);
-      xor_(scratch, scratch, t9);  // scratch is original left.
+      Addu(overflow_dst, zero_reg, right);
+      xor_(overflow_dst, scratch, overflow_dst);  // scratch is original left.
+      xor_(scratch, dst, scratch);                // scratch is original left.
       and_(overflow_dst, scratch, overflow_dst);
     } else {
       Subu(dst, left, right);
       xor_(overflow_dst, dst, left);
       // Load right since xori takes uint16 as immediate.
-      Addu(t9, zero_reg, right);
-      xor_(scratch, left, t9);
+      Addu(scratch, zero_reg, right);
+      xor_(scratch, left, scratch);
       and_(overflow_dst, scratch, overflow_dst);
     }
+    BranchOvfHelper(this, overflow_dst, overflow_label, no_overflow_label);
   }
 }
 
 
-void MacroAssembler::SubuAndCheckForOverflow(Register dst, Register left,
-                                             Register right,
-                                             Register overflow_dst,
-                                             Register scratch) {
+void MacroAssembler::SubBranchOvf(Register dst, Register left, Register right,
+                                  Label* overflow_label,
+                                  Label* no_overflow_label, Register scratch) {
+  DCHECK(overflow_label || no_overflow_label);
+  Register overflow_dst = t9;
+  DCHECK(!dst.is(scratch));
   DCHECK(!dst.is(overflow_dst));
-  DCHECK(!dst.is(scratch));
-  DCHECK(!overflow_dst.is(scratch));
+  DCHECK(!scratch.is(overflow_dst));
   DCHECK(!overflow_dst.is(left));
   DCHECK(!overflow_dst.is(right));
   DCHECK(!scratch.is(left));
   DCHECK(!scratch.is(right));
 
   // This happens with some crankshaft code. Since Subu works fine if
   // left == right, let's not make that restriction here.
   if (left.is(right)) {
     mov(dst, zero_reg);
-    mov(overflow_dst, zero_reg);
-    return;
+    if (no_overflow_label) {
+      Branch(no_overflow_label);
+    }
   }
 
   if (dst.is(left)) {
     mov(scratch, left);  // Preserve left.
     subu(dst, left, right);  // Left is overwritten.
     xor_(overflow_dst, dst, scratch);  // scratch is original left.
     xor_(scratch, scratch, right);  // scratch is original left.
     and_(overflow_dst, scratch, overflow_dst);
   } else if (dst.is(right)) {
     mov(scratch, right);  // Preserve right.
     subu(dst, left, right);  // Right is overwritten.
     xor_(overflow_dst, dst, left);
     xor_(scratch, left, scratch);  // Original right.
     and_(overflow_dst, scratch, overflow_dst);
   } else {
     subu(dst, left, right);
     xor_(overflow_dst, dst, left);
     xor_(scratch, left, right);
     and_(overflow_dst, scratch, overflow_dst);
   }
+  BranchOvfHelper(this, overflow_dst, overflow_label, no_overflow_label);
 }
 
 
 void MacroAssembler::CallRuntime(const Runtime::Function* f, int num_arguments,
                                  SaveFPRegsMode save_doubles,
                                  BranchDelaySlot bd) {
   // All parameters are on the stack. v0 has the return value after call.
 
   // If the expected number of arguments of the runtime function is
   // constant, we check that the actual number of arguments match the
@@ skipping 1373 matching lines @@
   if (mag.shift > 0) sra(result, result, mag.shift);
   srl(at, dividend, 31);
   Addu(result, result, Operand(at));
 }
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_MIPS