[clang] [clang][bytecode] Fix discarded Mulc/DivC opcodes (PR #180537)

[via cfe-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: Timm Baeder (tbaederr)

<details>
<summary>Changes</summary>

We need to pop the pointer in that case.

---
Full diff: https://github.com/llvm/llvm-project/pull/180537.diff


2 Files Affected:

- (modified) clang/lib/AST/ByteCode/Compiler.cpp (+10-2) 
- (modified) clang/test/AST/ByteCode/complex.cpp (+7) 


``````````diff
diff --git a/clang/lib/AST/ByteCode/Compiler.cpp b/clang/lib/AST/ByteCode/Compiler.cpp
index a0138c402e143..121ff00e462fc 100644
--- a/clang/lib/AST/ByteCode/Compiler.cpp
+++ b/clang/lib/AST/ByteCode/Compiler.cpp
@@ -1217,7 +1217,11 @@ bool Compiler<Emitter>::VisitComplexBinOp(const BinaryOperator *E) {
       return false;
     if (!this->visit(RHS))
       return false;
-    return this->emitMulc(ElemT, E);
+    if (!this->emitMulc(ElemT, E))
+      return false;
+    if (DiscardResult)
+      return this->emitPopPtr(E);
+    return true;
   }
 
   if (Op == BO_Div && RHSIsComplex) {
@@ -1254,7 +1258,11 @@ bool Compiler<Emitter>::VisitComplexBinOp(const BinaryOperator *E) {
 
     if (!this->visit(RHS))
       return false;
-    return this->emitDivc(ElemT, E);
+    if (!this->emitDivc(ElemT, E))
+      return false;
+    if (DiscardResult)
+      return this->emitPopPtr(E);
+    return true;
   }
 
   // Evaluate LHS and save value to LHSOffset.
diff --git a/clang/test/AST/ByteCode/complex.cpp b/clang/test/AST/ByteCode/complex.cpp
index 68a8e78d5b25b..9212c4fc47209 100644
--- a/clang/test/AST/ByteCode/complex.cpp
+++ b/clang/test/AST/ByteCode/complex.cpp
@@ -457,4 +457,11 @@ namespace Discard {
     return k;
   }
   static_assert(test_side_effect() == 1);
+
+  constexpr int discardedMulDiv() {
+    (void)(3 * 2i);
+    (void)(3 / 2i);
+    return 0;
+  }
+  static_assert(discardedMulDiv() == 0, "");
 }

``````````

</details>


https://github.com/llvm/llvm-project/pull/180537