[clang] [clang] Implement constexpr bit_cast for vectors (PR #66894)

[Richard Smith via cfe-commits]

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@@ -7095,6 +7096,21 @@ class APValueToBufferConverter {
     return true;
   }
 
+  bool visitVector(const APValue &Val, QualType Ty, CharUnits Offset) {
+    const auto *VT = Ty->castAs<VectorType>();
+
+    CharUnits ElemWidth = Info.Ctx.getTypeSizeInChars(VT->getElementType());
+    unsigned VectorLength = Val.getVectorLength();
+    // Visit each of the vector elements
+    for (unsigned I = 0; I != VectorLength; ++I) {
+      const APValue &SubObj = Val.getVectorElt(I);
+      if (!visit(SubObj, VT->getElementType(), Offset + I * ElemWidth))
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zygoloid wrote:

This isn't correct for a vector with element type `bool`, which Clang bit-packs.

https://github.com/llvm/llvm-project/pull/66894