MIPS: [wasm] Detect unrepresentability in the float32-to-int32 conversion correctly on arm

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

 // Copyright 2014 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 "src/ast/scopes.h"
 #include "src/compiler/code-generator.h"
 #include "src/compiler/code-generator-impl.h"
 #include "src/compiler/gap-resolver.h"
 #include "src/compiler/node-matchers.h"
 #include "src/compiler/osr.h"
@@ skipping 1310 matching lines @@
     case kMipsRoundWS: {
       FPURegister scratch = kScratchDoubleReg;
       __ round_w_s(scratch, i.InputDoubleRegister(0));
       __ mfc1(i.OutputRegister(), scratch);
       break;
     }
     case kMipsTruncWS: {
       FPURegister scratch = kScratchDoubleReg;
       __ trunc_w_s(scratch, i.InputDoubleRegister(0));
       __ mfc1(i.OutputRegister(), scratch);
+      // Avoid INT32_MAX as an overflow indicator and use INT32_MIN instead,
+      // because INT32_MIN allows easier out-of-bounds detection.
+      __ addiu(kScratchReg, i.OutputRegister(), 1);
+      __ slt(kScratchReg2, kScratchReg, i.OutputRegister());
+      __ Movn(i.OutputRegister(), kScratchReg, kScratchReg2);
       break;
     }
     case kMipsTruncUwD: {
       FPURegister scratch = kScratchDoubleReg;
       // TODO(plind): Fix wrong param order of Trunc_uw_d() macro-asm function.
       __ Trunc_uw_d(i.InputDoubleRegister(0), i.OutputRegister(), scratch);
       break;
     }
     case kMipsTruncUwS: {
       FPURegister scratch = kScratchDoubleReg;
       // TODO(plind): Fix wrong param order of Trunc_uw_s() macro-asm function.
       __ Trunc_uw_s(i.InputDoubleRegister(0), i.OutputRegister(), scratch);
+      // Avoid UINT32_MAX as an overflow indicator and use 0 instead,
+      // because 0 allows easier out-of-bounds detection.
+      __ addiu(kScratchReg, i.OutputRegister(), 1);
+      __ Movz(i.OutputRegister(), zero_reg, kScratchReg);
       break;
     }
     case kMipsFloat64ExtractLowWord32:
       __ FmoveLow(i.OutputRegister(), i.InputDoubleRegister(0));
       break;
     case kMipsFloat64ExtractHighWord32:
       __ FmoveHigh(i.OutputRegister(), i.InputDoubleRegister(0));
       break;
     case kMipsFloat64InsertLowWord32:
       __ FmoveLow(i.OutputDoubleRegister(), i.InputRegister(1));
@@ skipping 772 matching lines @@
       padding_size -= v8::internal::Assembler::kInstrSize;
     }
   }
 }
 
 #undef __
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8