[clang/test/CodeGen] Add test coverage for VarBypassDetector handling init statements and condition variables in switch clauses

[dwang]

Summary

VarBypassDetector.cpp lacks test coverage for handling init statements and condition variables in switch clauses, as is shown in:
https://lab.llvm.org/coverage/coverage-reports/coverage/Users/buildslave/jenkins/workspace/coverage/llvm-project/clang/lib/CodeGen/VarBypassDetector.cpp.html#L70
This patch adds test coverage for uncovered lines.

[dwang]

@vitalybuka Thanks for the quick review!

I need help landing this since I do not have commit permission.

clang/test/CodeGen/lifetime3.cpp

+// RUN: %clang_cc1 -S -emit-llvm -o - -O2 -disable-llvm-passes %s      | FileCheck %s --implicit-check-not="call void @llvm.lifetime" --check-prefixes=CHECK,O2
+// RUN: %clang_cc1 -S -emit-llvm -o - -O2 -disable-lifetime-markers %s | FileCheck %s --implicit-check-not="call void @llvm.lifetime" --check-prefixes=CHECK
+// RUN: %clang_cc1 -S -emit-llvm -o - -O0 %s                           | FileCheck %s --implicit-check-not="call void @llvm.lifetime" --check-prefixes=CHECK 
+
+extern int bar(char *A, int n);
+
+// CHECK-LABEL: @no_switch_bypass
+extern "C" void no_switch_bypass(int n) {
+  // O2: call void @llvm.lifetime.start.p0(i64 4,
+  switch (n += 1; int b=n) {
+  case 1: {
+    // O2: call void @llvm.lifetime.start.p0(i64 1,
+    // O2: call void @llvm.lifetime.end.p0(i64 1,
+    char x;
+    bar(&x, 1);
+    break;
+  }
+  case 2:
+    n = n;
+    // O2: call void @llvm.lifetime.start.p0(i64 5,
+    // O2: call void @llvm.lifetime.end.p0(i64 5,
+    char y[5];
+    bar(y, 5);
+    break;
+  }
+  // O2: call void @llvm.lifetime.end.p0(i64 4,
+}
+
+// CHECK-LABEL: @switch_bypass
+extern "C" void switch_bypass(int n) {
+  // O2: call void @llvm.lifetime.start.p0(i64 4,
+  // O2: call void @llvm.lifetime.end.p0(i64 4,
+  switch (n += 1; int b=n) {
+  case 1:
+    n = n;
+    char x;
+    bar(&x, 1);
+    break;
+  case 2:
+    bar(&x, 1);
+    break;
+  }
+}