Revert of MIPS: [turbofan] Fix addition for deoptimization. (patchset #3...

Revert of MIPS: [turbofan] Fix addition for deoptimization. (patchset #3 id:40001 of https://codereview.chromium.org/2102063002/ )

Reason for revert:
This workaround is no longer needed, port of e60c4053 fixes the issue.

Original issue's description:
> MIPS: [turbofan] Fix addition for deoptimization.
>
> In turbofan, after an addition operation where the same register is the
> output and both inputs, if deoptimization is performed the input is
> overwritten with the output value and the final result is not correct.
> This is fixed by restoring the original value of the input before
> deoptimization.
>
> BUG=
> TEST=mjsunit/regress/regress-int32-truncation
>
> Committed: https://crrev.com/99385e8e4bcef1f333ede61c936528bfc0c8ecfa
> Cr-Commit-Position: refs/heads/master@{#37524}

TBR=akos.palfi@imgtec.com,balazs.kilvady@imgtec.com,ivica.bogosavljevic@imgtec.com
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=

Review-Url: https://codereview.chromium.org/2129083003
Cr-Commit-Position: refs/heads/master@{#37612}

src/compiler/mips64/code-generator-mips64.cc

@@ -1803,21 +1803,10 @@ void CodeGenerator::AssembleArchBranch(Instruction* instr, BranchInfo* branch) {
     __ Branch(tlabel, cc, at, Operand(zero_reg));
   } else if (instr->arch_opcode() == kMips64Dadd ||
              instr->arch_opcode() == kMips64Dsub) {
-    Label done;
     cc = FlagsConditionToConditionOvf(branch->condition);
     __ dsra32(kScratchReg, i.OutputRegister(), 0);
     __ sra(at, i.OutputRegister(), 31);
-    __ Branch(&done, NegateCondition(cc), at, Operand(kScratchReg));
-    // If we deoptimize, check if output register is the same as input
-    // registers, if yes input values are overwritten so fix them first.
-    if (instr->InputAt(1)->IsRegister()) {
-      if (i.InputRegister(0).is(i.OutputRegister()) &&
-          i.InputRegister(1).is(i.OutputRegister())) {
-        __ dsra(i.OutputRegister(), i.OutputRegister(), 1);
-      }
-    }
-    __ Branch(tlabel);
-    __ bind(&done);
+    __ Branch(tlabel, cc, at, Operand(kScratchReg));
   } else if (instr->arch_opcode() == kMips64DaddOvf) {
     switch (branch->condition) {
       case kOverflow:

src/mips/macro-assembler-mips.cc

@@ -5493,14 +5493,11 @@ void MacroAssembler::AddBranchOvf(Register dst, Register left, Register right,
     DCHECK(!right.is(scratch));
 
     if (left.is(right) && dst.is(left)) {
-      mov(scratch, left);                // Preserve left and right.
-      addu(dst, left, right);            // Both are overwritten.
-      xor_(overflow_dst, dst, scratch);  // Left and right are equal.
-      Label done;                        // Restore inputs if overflow.
-      Branch(&done, ge, overflow_dst, Operand(zero_reg));
-      mov(left, scratch);  // Original left and right.
-      bind(&done);
-    } else if (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.