[clang] [clang][bytecode] Implement fixed-point-to-float casts (PR #110369)

[Timm Baeder via cfe-commits]

https://github.com/tbaederr created https://github.com/llvm/llvm-project/pull/110369

None

>From af2fe551a5324cd1274e1da8d6a14303646ae5b6 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Timm=20B=C3=A4der?= <tbaeder at redhat.com>
Date: Sat, 28 Sep 2024 16:02:56 +0200
Subject: [PATCH] [clang][bytecode] Implement fixed-point-to-float casts

---
 clang/lib/AST/ByteCode/Compiler.cpp     | 6 ++++++
 clang/lib/AST/ByteCode/FixedPoint.h     | 4 ++++
 clang/lib/AST/ByteCode/Interp.h         | 8 ++++++++
 clang/lib/AST/ByteCode/Opcodes.td       | 3 +++
 clang/test/AST/ByteCode/fixed-point.cpp | 3 +++
 5 files changed, 24 insertions(+)

diff --git a/clang/lib/AST/ByteCode/Compiler.cpp b/clang/lib/AST/ByteCode/Compiler.cpp
index 40cb1b2dd80f96..77bfb3d8cd7f1a 100644
--- a/clang/lib/AST/ByteCode/Compiler.cpp
+++ b/clang/lib/AST/ByteCode/Compiler.cpp
@@ -691,6 +691,12 @@ bool Compiler<Emitter>::VisitCastExpr(const CastExpr *CE) {
     std::memcpy(&I, &Sem, sizeof(Sem));
     return this->emitCastFloatingFixedPoint(I, CE);
   }
+  case CK_FixedPointToFloating: {
+    if (!this->visit(SubExpr))
+      return false;
+    const auto *TargetSemantics = &Ctx.getFloatSemantics(CE->getType());
+    return this->emitCastFixedPointFloating(TargetSemantics, CE);
+  }
 
   case CK_ToVoid:
     return discard(SubExpr);
diff --git a/clang/lib/AST/ByteCode/FixedPoint.h b/clang/lib/AST/ByteCode/FixedPoint.h
index daa62945346aeb..fb8457a08e93cc 100644
--- a/clang/lib/AST/ByteCode/FixedPoint.h
+++ b/clang/lib/AST/ByteCode/FixedPoint.h
@@ -52,6 +52,10 @@ class FixedPoint final {
   unsigned bitWidth() const { return V.getWidth(); }
   bool isSigned() const { return V.isSigned(); }
 
+  llvm::APFloat toFloat(const llvm::fltSemantics *Sem) const {
+    return V.convertToFloat(*Sem);
+  }
+
   ComparisonCategoryResult compare(const FixedPoint &Other) const {
     if (Other.V == V)
       return ComparisonCategoryResult::Equal;
diff --git a/clang/lib/AST/ByteCode/Interp.h b/clang/lib/AST/ByteCode/Interp.h
index 23405765d8de82..0a99d9440ff844 100644
--- a/clang/lib/AST/ByteCode/Interp.h
+++ b/clang/lib/AST/ByteCode/Interp.h
@@ -2367,6 +2367,14 @@ static inline bool CastFloatingFixedPoint(InterpState &S, CodePtr OpPC,
   return true;
 }
 
+static inline bool CastFixedPointFloating(InterpState &S, CodePtr OpPC,
+                                          const llvm::fltSemantics *Sem) {
+  const auto &Fixed = S.Stk.pop<FixedPoint>();
+
+  S.Stk.push<Floating>(Fixed.toFloat(Sem));
+  return true;
+}
+
 static inline bool PtrPtrCast(InterpState &S, CodePtr OpPC, bool SrcIsVoidPtr) {
   const auto &Ptr = S.Stk.peek<Pointer>();
 
diff --git a/clang/lib/AST/ByteCode/Opcodes.td b/clang/lib/AST/ByteCode/Opcodes.td
index 240e00e59d97ec..4f11b927989004 100644
--- a/clang/lib/AST/ByteCode/Opcodes.td
+++ b/clang/lib/AST/ByteCode/Opcodes.td
@@ -682,6 +682,9 @@ def CastIntegralFixedPoint : Opcode {
 def CastFloatingFixedPoint : Opcode {
   let Args = [ArgUint32];
 }
+def CastFixedPointFloating : Opcode {
+  let Args = [ArgFltSemantics];
+}
 
 def PtrPtrCast : Opcode {
   let Args = [ArgBool];
diff --git a/clang/test/AST/ByteCode/fixed-point.cpp b/clang/test/AST/ByteCode/fixed-point.cpp
index 76da06a02e150c..68137618b5db60 100644
--- a/clang/test/AST/ByteCode/fixed-point.cpp
+++ b/clang/test/AST/ByteCode/fixed-point.cpp
@@ -31,4 +31,7 @@ namespace FloatToFixedPointCast {
                              // both-note {{outside the range of representable values of type 'const _Fract'}}
 
   constexpr _Fract sf2 = 0.5;
+  static_assert(sf2 == 0.5);
+  constexpr float sf2f = sf2;
+  static_assert(sf2f == 0.5);
 }