Subzero: fix calling C functions on Windows x64

src/Reactor/SubzeroReactor.cpp

@@ -160,7 +160,7 @@ namespace rr
 {
 	const Capabilities Caps =
 	{
-		false, // CallSupported
+		true, // CallSupported
 		false, // CoroutinesSupported
 	};
 

third_party/subzero/src/IceTargetLoweringX8632Traits.h

@@ -694,6 +694,12 @@ public:
     (void)ArgNum;
     return RegNumT();
   }
+  // Given the absolute argument position and argument position by type, return
+  // the register index to assign it to.
+  static SizeT getArgIndex(SizeT argPos, SizeT argPosByType) {
+    (void)argPos;
+    return argPosByType;
+  };
 
   /// The number of bits in a byte
   static constexpr uint32_t X86_CHAR_BIT = 8;

third_party/subzero/src/IceTargetLoweringX8664Traits.h

@@ -742,6 +742,15 @@ public:
     assert(Ty == IceType_i64 || Ty == IceType_i32);
     return getGprForType(Ty, GprForArgNum[ArgNum]);
   }
+  // Given the absolute argument position and argument position by type, return
+  // the register index to assign it to.
+  static SizeT getArgIndex(SizeT argPos, SizeT argPosByType) {
+    // Microsoft x64 ABI: register is selected by arg position (e.g. 1st int as
+    // 2nd param goes into 2nd int reg)
+    (void)argPosByType;
+    return argPos;
+  };
+
 #else
   // System V x86-64 calling convention:
   //
@@ -774,6 +783,12 @@ public:
     assert(Ty == IceType_i64 || Ty == IceType_i32);
     return getGprForType(Ty, GprForArgNum[ArgNum]);
   }
+  // Given the absolute argument position and argument position by type, return
+  // the register index to assign it to.
+  static SizeT getArgIndex(SizeT argPos, SizeT argPosByType) {
+    (void)argPos;
+    return argPosByType;
+  }
 #endif
 
   /// Whether scalar floating point arguments are passed in XMM registers