[PATCH] D24311: Implement MS _rot intrinsics

[David Majnemer via cfe-commits]

majnemer added inline comments.

================
Comment at: lib/AST/ExprConstant.cpp:7024-7050
@@ -7023,1 +7023,29 @@
 
+  case Builtin::BI_rotl8:
+  case Builtin::BI_rotl16:
+  case Builtin::BI_rotl:
+  case Builtin::BI_lrotl:
+  case Builtin::BI_rotl64: {
+    APSInt Val, Shift;
+    if (!EvaluateInteger(E->getArg(0), Val, Info) ||
+        !EvaluateInteger(E->getArg(1), Shift, Info))
+      return false;
+
+    APSInt BitWidth(llvm::APInt(32, Val.getBitWidth()));
+    return Success(Val.rotl(Shift % BitWidth), E);
+  }
+
+  case Builtin::BI_rotr8:
+  case Builtin::BI_rotr16:
+  case Builtin::BI_rotr:
+  case Builtin::BI_lrotr:
+  case Builtin::BI_rotr64: {
+    APSInt Val, Shift;
+    if (!EvaluateInteger(E->getArg(0), Val, Info) ||
+        !EvaluateInteger(E->getArg(1), Shift, Info))
+      return false;
+
+    APSInt BitWidth(llvm::APInt(32, Val.getBitWidth()));
+    return Success(Val.rotr(Shift % BitWidth), E);
+  }
+
----------------
Any reason why we need this?

Given:
  #include <intrin.h>

  constexpr int x = _rotl8(1, 2);

MSVC 2015 reports:
  error C2131: expression did not evaluate to a constant


https://reviews.llvm.org/D24311