MIPS: [turbofan] Improve test and equality compare with zero and constants.

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

Index: src/compiler/mips/code-generator-mips.cc
diff --git a/src/compiler/mips/code-generator-mips.cc b/src/compiler/mips/code-generator-mips.cc
index 7769b9e739ec5873e47b32a0e9060082e7350e5e..d6d5ac5b2097b9142c9196bc578402bb85c9c75a 100644
--- a/src/compiler/mips/code-generator-mips.cc
+++ b/src/compiler/mips/code-generator-mips.cc
@@ -968,19 +968,10 @@ void CodeGenerator::AssembleArchBoolean(Instruction* instr,
   if (instr->arch_opcode() == kMipsTst) {
     cc = FlagsConditionToConditionTst(condition);
     __ And(kScratchReg, i.InputRegister(0), i.InputOperand(1));
-    __ xori(result, zero_reg, 1);  // Create 1 for true.
-    if (IsMipsArchVariant(kMips32r6)) {
-      if (cc == eq) {
-        __ seleqz(result, result, kScratchReg);
-      } else {
-        __ selnez(result, result, kScratchReg);
-      }
-    } else {
-      if (cc == eq) {
-        __ Movn(result, zero_reg, kScratchReg);
-      } else {
-        __ Movz(result, zero_reg, kScratchReg);
-      }
+    __ Sltu(result, zero_reg, kScratchReg);
+    if (cc == eq) {
+      // Sltu produces 0 for equality, invert the result.
+      __ xori(result, result, 1);
     }
     return;
   } else if (instr->arch_opcode() == kMipsAddOvf ||
@@ -999,20 +990,18 @@ void CodeGenerator::AssembleArchBoolean(Instruction* instr,
       case ne: {
         Register left = i.InputRegister(0);
         Operand right = i.InputOperand(1);
-        __ Subu(kScratchReg, left, right);
-        __ xori(result, zero_reg, 1);
-        if (IsMipsArchVariant(kMips32r6)) {
-          if (cc == eq) {
-            __ seleqz(result, result, kScratchReg);
-          } else {
-            __ selnez(result, result, kScratchReg);
-          }
+        Register select;
+        if (instr->InputAt(1)->IsImmediate() && right.immediate() == 0) {
+          // Pass left operand if right is zero.
+          select = left;
         } else {
-          if (cc == eq) {
-            __ Movn(result, zero_reg, kScratchReg);
-          } else {
-            __ Movz(result, zero_reg, kScratchReg);
-          }
+          __ Subu(kScratchReg, left, right);
+          select = kScratchReg;
+        }
+        __ Sltu(result, zero_reg, select);
+        if (cc == eq) {
+          // Sltu produces 0 for equality, invert the result.
+          __ xori(result, result, 1);
         }
       } break;
       case lt: