QmlCompiler: Avoid infinite loop in dead store elimination

We have to mark the required variables also in block 0. And we shouldn't
generate empty blocks.

Fixes: QTBUG-101011
Change-Id: I0dd19f69f45f507cb83e2ddfba3060de48a940b4
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>
(cherry picked from commit 88147eb3f621e7d972410698d6edca16493d7c66)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

1 files changed, 6 insertions, 3 deletions

diff --git a/src/qmlcompiler/qqmljscodegenerator.cpp b/src/qmlcompiler/qqmljscodegenerator.cpp
index 93b69474db..d87b2a38ad 100644
--- a/src/qmlcompiler/qqmljscodegenerator.cpp
+++ b/src/qmlcompiler/qqmljscodegenerator.cpp
@@ -184,9 +184,11 @@ QList<QQmlJSCodeGenerator::BasicBlock> QQmlJSCodeGenerator::findBasicBlocks(
         const QQmlJSCodeGenerator::Section &section = sections[i];
         const QString label = section.label();
         if (!label.isEmpty() || currentBlock.jumpMode != JumpMode::None) {
-            currentBlock.endSection = i;
-            basicBlocks.append(currentBlock);
-            currentBlock.beginSection = i;
+            if (currentBlock.beginSection != i) {
+                currentBlock.endSection = i;
+                basicBlocks.append(currentBlock);
+                currentBlock.beginSection = i;
+            }
             currentBlock.label = label;
         }
         currentBlock.jumpMode = section.jumpMode();
@@ -320,6 +322,7 @@ void QQmlJSCodeGenerator::eliminateDeadStores()
                         usedOnce = true;
                     }
                 }
+                requiredRegisters[0][variable] = inUse;
 
                 if (!usedOnce) {
                     registerTypeIt = registerTypes.erase(registerTypeIt);