[clang] [Coverage][NFC] Avoid visiting non-unique `OpaqueValueExpr` (PR #88910)

[Andrey Ali Khan Bolshakov via cfe-commits]

https://github.com/bolshakov-a created https://github.com/llvm/llvm-project/pull/88910

Only unique `OpaqueValueExpr`s should be handled in the mapping builder, as [discussed](https://github.com/llvm/llvm-project/pull/85837#discussion_r1542056451) in #85837. However, `getCond()` returns non-unique `OpaqueValueExpr` for `BinaryConditionalOperator` (because it is also used as the "true" branch expression). Use `getCommon()` instead so as to bypass the `OpaqueValueExpr`.

@efriedma-quic 

>From da7a72d3a9918f83e112a55f7ce60da5f015c56c Mon Sep 17 00:00:00 2001
From: Bolshakov <bolsh.andrey at yandex.ru>
Date: Tue, 16 Apr 2024 18:13:49 +0300
Subject: [PATCH] [Coverage][NFC] Avoid visiting non-unique `OpaqueValueExpr`

Only unique `OpaqueValueExpr`s should be handled in the mapping
builder, as discussed in #85837. However, `getCond()` returns
non-unique `OpaqueValueExpr` for `BinaryConditionalOperator` (because
it is also used as the "true" branch expression). Use `getCommon()`
instead so as to bypass the `OpaqueValueExpr`.
---
 clang/lib/CodeGen/CoverageMappingGen.cpp | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/clang/lib/CodeGen/CoverageMappingGen.cpp b/clang/lib/CodeGen/CoverageMappingGen.cpp
index 71215da362d3d0..64c39c5de351c7 100644
--- a/clang/lib/CodeGen/CoverageMappingGen.cpp
+++ b/clang/lib/CodeGen/CoverageMappingGen.cpp
@@ -2011,11 +2011,13 @@ struct CounterCoverageMappingBuilder
     Counter TrueCount = llvm::EnableSingleByteCoverage
                             ? getRegionCounter(E->getTrueExpr())
                             : getRegionCounter(E);
-
-    propagateCounts(ParentCount, E->getCond());
     Counter OutCount;
 
-    if (!isa<BinaryConditionalOperator>(E)) {
+    if (const auto *BCO = dyn_cast<BinaryConditionalOperator>(E)) {
+      propagateCounts(ParentCount, BCO->getCommon());
+      OutCount = TrueCount;
+    } else {
+      propagateCounts(ParentCount, E->getCond());
       // The 'then' count applies to the area immediately after the condition.
       auto Gap =
           findGapAreaBetween(E->getQuestionLoc(), getStart(E->getTrueExpr()));
@@ -2024,8 +2026,6 @@ struct CounterCoverageMappingBuilder
 
       extendRegion(E->getTrueExpr());
       OutCount = propagateCounts(TrueCount, E->getTrueExpr());
-    } else {
-      OutCount = TrueCount;
     }
 
     extendRegion(E->getFalseExpr());