[PATCH] D71049: Remove implicit conversion that promotes half to other larger precision types for fp classification builtins

[Jim Lin via Phabricator via cfe-commits]

Jim created this revision.
Jim added a reviewer: aaron.ballman.
Herald added a project: clang.
Herald added a subscriber: cfe-commits.

It shouldn't promote half to double or any larger precision types for fp classification builtins.
Because fp classification builtins would get incorrect result with promoted argument.
For example, __builtin_isnormal with a subnormal half value should return false, but it is not.
That the subnormal half value is promoted to a normal double value.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D71049

Files:
  clang/lib/Sema/SemaChecking.cpp


Index: clang/lib/Sema/SemaChecking.cpp
===================================================================
--- clang/lib/Sema/SemaChecking.cpp
+++ clang/lib/Sema/SemaChecking.cpp
@@ -5808,7 +5808,7 @@
            << OrigArg->getType() << OrigArg->getSourceRange();
 
   // If this is an implicit conversion from float -> float, double, or
-  // long double, remove it.
+  // long double, or half -> half, float, double, or long double, remove it.
   if (ImplicitCastExpr *Cast = dyn_cast<ImplicitCastExpr>(OrigArg)) {
     // Only remove standard FloatCasts, leaving other casts inplace
     if (Cast->getCastKind() == CK_FloatingCast) {
@@ -5823,6 +5823,18 @@
         Cast->setSubExpr(nullptr);
         TheCall->setArg(NumArgs-1, CastArg);
       }
+
+      if (CastArg->getType()->isSpecificBuiltinType(BuiltinType::Half)) {
+        assert(
+            (Cast->getType()->isSpecificBuiltinType(BuiltinType::Double) ||
+             Cast->getType()->isSpecificBuiltinType(BuiltinType::Float) ||
+             Cast->getType()->isSpecificBuiltinType(BuiltinType::Half) ||
+             Cast->getType()->isSpecificBuiltinType(BuiltinType::LongDouble)) &&
+            "promotion from half to either half, float, double, or long double "
+            "is the only expected cast here");
+        Cast->setSubExpr(nullptr);
+        TheCall->setArg(NumArgs-1, CastArg);
+      }
     }
   }
 


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