[PATCH] D66862: Make lround builtin constexpr (and others)

[Zoe Carver via Phabricator via cfe-commits]

zoecarver updated this revision to Diff 217973.
zoecarver added a comment.

- remove rint updates (rint uses runtime-defined rounding method)
- add more tests (nan, overflow, round down)
- use APFloat rounding methods
- if rounding fails, bail out to runtime


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D66862/new/

https://reviews.llvm.org/D66862

Files:
  clang/lib/AST/ExprConstant.cpp
  clang/test/SemaCXX/math-builtins.cpp


Index: clang/test/SemaCXX/math-builtins.cpp
===================================================================
--- /dev/null
+++ clang/test/SemaCXX/math-builtins.cpp
@@ -0,0 +1,32 @@
+// RUN: %clang_cc1 -std=c++11 %s
+
+int main()
+{
+  constexpr float f1 = 12345.6789;
+  constexpr float f2 = 12345.4321;
+
+  static_assert(__builtin_llround(f1) == 12346, "");
+  static_assert(__builtin_llroundf(f1) == 12346, "");
+
+  static_assert(__builtin_lround(f1) == 12346, "");
+  static_assert(__builtin_lroundf(f1) == 12346, "");
+
+  static_assert(__builtin_llround(f2) == 12345, "");
+  static_assert(__builtin_llroundf(f2) == 12345, "");
+
+  static_assert(__builtin_lround(f2) == 12345, "");
+  static_assert(__builtin_lroundf(f2) == 12345, "");
+
+  static_assert(__builtin_llround(float()) == 0, ""); // expected-error {{static_assert expression is not an integral constant expression}}
+  static_assert(__builtin_llroundf(float()) == 0, ""); // expected-error {{static_assert expression is not an integral constant expression}}
+
+  static_assert(__builtin_lround(float()) == 0, ""); // expected-error {{static_assert expression is not an integral constant expression}}
+  static_assert(__builtin_lroundf(float()) == 0, ""); // expected-error {{static_assert expression is not an integral constant expression}}
+
+  // TODO: expected-error not working
+  static_assert(__builtin_llround(__FLT_MAX__) == 0, ""); // expected-error {{static_assert expression is not an integral constant expression}}
+  static_assert(__builtin_llroundf(__FLT_MAX__) == 0, ""); // expected-error {{static_assert expression is not an integral constant expression}}
+
+  static_assert(__builtin_lround(__FLT_MAX__) == 0, ""); // expected-error {{static_assert expression is not an integral constant expression}}
+  static_assert(__builtin_lroundf(__FLT_MAX__) == 0, ""); // expected-error {{static_assert expression is not an integral constant expression}}
+}
\ No newline at end of file
Index: clang/lib/AST/ExprConstant.cpp
===================================================================
--- clang/lib/AST/ExprConstant.cpp
+++ clang/lib/AST/ExprConstant.cpp
@@ -9609,6 +9609,22 @@
     return Success(N == Val.getBitWidth() ? 0 : N + 1, E);
   }
 
+  case Builtin::BI__builtin_lround:
+  case Builtin::BI__builtin_lroundf:
+  case Builtin::BI__builtin_llround:
+  case Builtin::BI__builtin_llroundf: {
+    APFloat FPVal(0.0);
+    APSInt IVal(64, 0); // TODO: dynamically get correct size here?
+    bool isExact = true;
+
+    if(!EvaluateFloat(E->getArg(0), FPVal, Info)) return false;
+    APFloat::opStatus status =
+        FPVal.convertToInteger(IVal, APFloat::rmNearestTiesToAway, &isExact);
+    if(status != APFloat::opInexact && status != APFloat::opOK) return false;
+
+    return Success(IVal.getExtValue(), E);
+  }
+
   case Builtin::BI__builtin_fpclassify: {
     APFloat Val(0.0);
     if (!EvaluateFloat(E->getArg(5), Val, Info))


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