[clang] [clang][bytecode] Fix DiscardResult handling in fixed-point operations (PR #195013)

[Timm Baeder via cfe-commits]

https://github.com/tbaederr created https://github.com/llvm/llvm-project/pull/195013

None

>From 751656f0a10de6d0d892f53a5bd83e9377c34cc2 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Timm=20B=C3=A4der?= <tbaeder at redhat.com>
Date: Thu, 30 Apr 2026 08:24:37 +0200
Subject: [PATCH] [clang][bytecode] Fix DiscardResult handling in fixed-point
 operations

---
 clang/lib/AST/ByteCode/Compiler.cpp     | 39 ++++++++++++++++++++-----
 clang/test/AST/ByteCode/fixed-point.cpp |  1 +
 2 files changed, 33 insertions(+), 7 deletions(-)

diff --git a/clang/lib/AST/ByteCode/Compiler.cpp b/clang/lib/AST/ByteCode/Compiler.cpp
index 349bbed6830ba..626068ce9eee5 100644
--- a/clang/lib/AST/ByteCode/Compiler.cpp
+++ b/clang/lib/AST/ByteCode/Compiler.cpp
@@ -773,8 +773,12 @@ bool Compiler<Emitter>::VisitCastExpr(const CastExpr *E) {
 
     auto Sem =
         Ctx.getASTContext().getFixedPointSemantics(E->getType()).toOpaqueInt();
-    return this->emitCastIntegralFixedPoint(classifyPrim(SubExpr->getType()),
-                                            Sem, E);
+    if (!this->emitCastIntegralFixedPoint(classifyPrim(SubExpr->getType()), Sem,
+                                          E))
+      return false;
+    if (DiscardResult)
+      return this->emitPopFixedPoint(E);
+    return true;
   }
   case CK_FloatingToFixedPoint: {
     if (!this->visit(SubExpr))
@@ -782,25 +786,42 @@ bool Compiler<Emitter>::VisitCastExpr(const CastExpr *E) {
 
     auto Sem =
         Ctx.getASTContext().getFixedPointSemantics(E->getType()).toOpaqueInt();
-    return this->emitCastFloatingFixedPoint(Sem, E);
+    if (!this->emitCastFloatingFixedPoint(Sem, E))
+      return false;
+    if (DiscardResult)
+      return this->emitPopFixedPoint(E);
+    return true;
   }
   case CK_FixedPointToFloating: {
     if (!this->visit(SubExpr))
       return false;
     const auto *TargetSemantics = &Ctx.getFloatSemantics(E->getType());
-    return this->emitCastFixedPointFloating(TargetSemantics, E);
+    if (!this->emitCastFixedPointFloating(TargetSemantics, E))
+      return false;
+    if (DiscardResult)
+      return this->emitPopFloat(E);
+    return true;
   }
   case CK_FixedPointToIntegral: {
     if (!this->visit(SubExpr))
       return false;
-    return this->emitCastFixedPointIntegral(classifyPrim(E->getType()), E);
+    PrimType IntegralT = classifyPrim(E->getType());
+    if (!this->emitCastFixedPointIntegral(IntegralT, E))
+      return false;
+    if (DiscardResult)
+      return this->emitPop(IntegralT, E);
+    return true;
   }
   case CK_FixedPointCast: {
     if (!this->visit(SubExpr))
       return false;
     auto Sem =
         Ctx.getASTContext().getFixedPointSemantics(E->getType()).toOpaqueInt();
-    return this->emitCastFixedPoint(Sem, E);
+    if (!this->emitCastFixedPoint(Sem, E))
+      return false;
+    if (DiscardResult)
+      return this->emitPopFixedPoint(E);
+    return true;
   }
 
   case CK_ToVoid:
@@ -1902,7 +1923,11 @@ bool Compiler<Emitter>::VisitFixedPointUnaryOperator(const UnaryOperator *E) {
   case UO_Minus:
     if (!this->visit(SubExpr))
       return false;
-    return this->emitNegFixedPoint(E);
+    if (!this->emitNegFixedPoint(E))
+      return false;
+    if (DiscardResult)
+      return this->emitPopFixedPoint(E);
+    return true;
   default:
     return false;
   }
diff --git a/clang/test/AST/ByteCode/fixed-point.cpp b/clang/test/AST/ByteCode/fixed-point.cpp
index 5237d758fa257..c8baa1972536a 100644
--- a/clang/test/AST/ByteCode/fixed-point.cpp
+++ b/clang/test/AST/ByteCode/fixed-point.cpp
@@ -12,6 +12,7 @@ static_assert(1.0k != 1); // both-error {{failed due to requirement '1.0k != 1'}
 static_assert(-12.0k == -(-(-12.0k)));
 
 constexpr _Accum acc = (0.5r, 6.9k);
+constexpr _Accum acc2 = (-1e+00r, 2.3);
 
 /// Zero-init.
 constexpr _Accum A{};