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

src/mips/macro-assembler-mips.cc

Index: src/mips/macro-assembler-mips.cc
diff --git a/src/mips/macro-assembler-mips.cc b/src/mips/macro-assembler-mips.cc
index 14d8ed8e1e024289391ec97f4d0ad98ab8e96072..9b64fd8facbe6c588bb913c51abb46fdcca4e9bc 100644
--- a/src/mips/macro-assembler-mips.cc
+++ b/src/mips/macro-assembler-mips.cc
@@ -4297,70 +4297,104 @@ void MacroAssembler::SmiToDoubleFPURegister(Register smi,
 }
 
 
-void MacroAssembler::AdduAndCheckForOverflow(Register dst, Register left,
-                                             const Operand& right,
-                                             Register overflow_dst,
-                                             Register scratch) {
+void MacroAssembler::AdduAndCheckForOverflow(
+    Register dst, Register left, const Operand& right, Label* overflow_label,
+    Label* no_overflow_label, Register scratch, BranchDelaySlot bd) {
+  DCHECK(overflow_label || no_overflow_label);
   if (right.is_reg()) {
-    AdduAndCheckForOverflow(dst, left, right.rm(), overflow_dst, scratch);
+    AdduAndCheckForOverflow(dst, left, right.rm(), overflow_label,
+                            no_overflow_label, scratch, bd);
   } 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)) {
+      DCHECK(!left.is(t9));
+      Register right_reg = t9;
+      li(right_reg, Operand(right));
+      AdduAndCheckForOverflow(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;
+      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);
+      }
+      Branch(overflow_label, lt, overflow_dst, Operand(zero_reg));
+      if (no_overflow_label) bc(no_overflow_label);

[paul.l..., 2015/11/13 02:16:20]

This is not r6, you cannot use 'bc' here can you?

I think you have to use Branch(), (which I believe would emit bc() on r6 if no
delay-slot usage, you;ve already tested for r6 above, and we are not there).

     }
   }
 }
 
 
-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));
-
-  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 (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);
+void MacroAssembler::AdduAndCheckForOverflow(
+    Register dst, Register left, Register right, Label* overflow_label,
+    Label* no_overflow_label, Register scratch, BranchDelaySlot bd) {
+  if (IsMipsArchVariant(kMips32r6)) {
+    if (!overflow_label) {
+      DCHECK(no_overflow_label);
+      DCHECK(!dst.is(scratch));
+      DCHECK(!dst.is(t9));
+      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 {
-    addu(dst, left, right);
-    xor_(overflow_dst, dst, left);
-    xor_(scratch, dst, right);
-    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));
+    DCHECK(!right.is(overflow_dst));
+
+    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 (!overflow_label) {
+      DCHECK(no_overflow_label);
+      Branch(no_overflow_label, ge, overflow_dst, Operand(zero_reg));
+    } else {
+      Branch(overflow_label, lt, overflow_dst, Operand(zero_reg));
+      if (no_overflow_label) bc(no_overflow_label);
+    }
   }
 }