X87: [turbofan] Add support for reinterpreting integers as floating point and vice versa.

src/compiler/x87/code-generator-x87.cc

Index: src/compiler/x87/code-generator-x87.cc
diff --git a/src/compiler/x87/code-generator-x87.cc b/src/compiler/x87/code-generator-x87.cc
index 596b7ab775343b251f55e1014dfce84ddcbe78e0..c0a6303dd8bb9d9fe2a072d10b6dc26d7fa842de 100644
--- a/src/compiler/x87/code-generator-x87.cc
+++ b/src/compiler/x87/code-generator-x87.cc
@@ -1069,6 +1069,28 @@ void CodeGenerator::AssembleArchInstruction(Instruction* instr) {
       }
       break;
     }
+    case kX87BitcastFI: {
+      __ fstp(0);
+      __ mov(i.OutputRegister(), MemOperand(esp, 0));
+      __ lea(esp, Operand(esp, kFloatSize));
+      break;
+    }
+    case kX87BitcastIF: {
+      if (instr->InputAt(0)->IsRegister()) {
+        __ lea(esp, Operand(esp, -kFloatSize));
+        __ mov(MemOperand(esp, 0), i.InputRegister(0));
+        __ fstp(0);
+        __ fld_s(MemOperand(esp, 0));
+        __ lea(esp, Operand(esp, kFloatSize));
+      } else {
+        __ lea(esp, Operand(esp, -kDoubleSize));
+        __ mov(MemOperand(esp, 0), i.InputRegister(0));
+        __ fstp(0);
+        __ fld_d(MemOperand(esp, 0));
+        __ lea(esp, Operand(esp, kDoubleSize));
+      }
+      break;
+    }
     case kX87Lea: {
       AddressingMode mode = AddressingModeField::decode(instr->opcode());
       // Shorten "leal" to "addl", "subl" or "shll" if the register allocation