[Fixed Point Arithmetic] Fixed Point and Integer Conversions

This patch includes the necessary code for converting between a fixed point type and integer.
This also includes constant expression evaluation for conversions with these types.

Differential Revision: https://reviews.llvm.org/D56900

llvm-svn: 355462

1 files changed, 37 insertions, 0 deletions

diff --git a/clang/lib/Basic/FixedPoint.cpp b/clang/lib/Basic/FixedPoint.cpp
index ca84a0cf483..f049e6f64a5 100644
--- a/clang/lib/Basic/FixedPoint.cpp
+++ b/clang/lib/Basic/FixedPoint.cpp
@@ -218,4 +218,41 @@ APFixedPoint APFixedPoint::negate(bool *Overflow) const {
     return APFixedPoint(Sema);
 }
 
+llvm::APSInt APFixedPoint::convertToInt(unsigned DstWidth, bool DstSign,
+                                        bool *Overflow) const {
+  llvm::APSInt Result = getIntPart();
+  unsigned SrcWidth = getWidth();
+
+  llvm::APSInt DstMin = llvm::APSInt::getMinValue(DstWidth, !DstSign);
+  llvm::APSInt DstMax = llvm::APSInt::getMaxValue(DstWidth, !DstSign);
+
+  if (SrcWidth < DstWidth) {
+    Result = Result.extend(DstWidth);
+  } else if (SrcWidth > DstWidth) {
+    DstMin = DstMin.extend(SrcWidth);
+    DstMax = DstMax.extend(SrcWidth);
+  }
+
+  if (Overflow) {
+    if (Result.isSigned() && !DstSign) {
+      *Overflow = Result.isNegative() || Result.ugt(DstMax);
+    } else if (Result.isUnsigned() && DstSign) {
+      *Overflow = Result.ugt(DstMax);
+    } else {
+      *Overflow = Result < DstMin || Result > DstMax;
+    }
+  }
+
+  Result.setIsSigned(DstSign);
+  return Result.extOrTrunc(DstWidth);
+}
+
+APFixedPoint APFixedPoint::getFromIntValue(const llvm::APSInt &Value,
+                                           const FixedPointSemantics &DstFXSema,
+                                           bool *Overflow) {
+  FixedPointSemantics IntFXSema = FixedPointSemantics::GetIntegerSemantics(
+      Value.getBitWidth(), Value.isSigned());
+  return APFixedPoint(Value, IntFXSema).convert(DstFXSema, Overflow);
+}
+
 }  // namespace clang