[clang] [clang][bytecode] Fix ignoring comparisons in C (PR #156180)

[Timm Baeder via cfe-commits]

https://github.com/tbaederr created https://github.com/llvm/llvm-project/pull/156180

Our comparison ops always return bool, and we do the pop before the conversion to in in C.

Fixes #156178

>From a8c9f87454c4ecb382e465b4cfc6ccd6a7787130 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Timm=20B=C3=A4der?= <tbaeder at redhat.com>
Date: Sat, 30 Aug 2025 15:28:38 +0200
Subject: [PATCH] [clang][bytecode] Fix ignoring comparisons in C

Our comparison ops always return bool, and we do the pop before the
conversion to in in C.

Fixes #156178
---
 clang/lib/AST/ByteCode/Compiler.cpp | 2 +-
 clang/test/AST/ByteCode/c.c         | 6 ++++++
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/clang/lib/AST/ByteCode/Compiler.cpp b/clang/lib/AST/ByteCode/Compiler.cpp
index c314f0a132196..56552f3969216 100644
--- a/clang/lib/AST/ByteCode/Compiler.cpp
+++ b/clang/lib/AST/ByteCode/Compiler.cpp
@@ -942,7 +942,7 @@ bool Compiler<Emitter>::VisitBinaryOperator(const BinaryOperator *BO) {
     if (!Result)
       return false;
     if (DiscardResult)
-      return this->emitPop(*T, BO);
+      return this->emitPopBool(BO);
     if (T != PT_Bool)
       return this->emitCast(PT_Bool, *T, BO);
     return true;
diff --git a/clang/test/AST/ByteCode/c.c b/clang/test/AST/ByteCode/c.c
index 05af00c040f45..b6d2a69271afb 100644
--- a/clang/test/AST/ByteCode/c.c
+++ b/clang/test/AST/ByteCode/c.c
@@ -362,3 +362,9 @@ void bar() { // pedantic-warning {{a function declaration without a prototype}}
   int x;
   x = foo(); // all-warning {{too few arguments}}
 }
+
+int *_b = &a;
+void discardedCmp(void)
+{
+    (*_b) = ((&a == &a) , a); // all-warning {{left operand of comma operator has no effect}}
+}