make switch constant folding a bit stronger, handling a missed case.

llvm-svn: 126638

2 files changed, 25 insertions, 4 deletions

diff --git a/clang/lib/CodeGen/CGStmt.cpp b/clang/lib/CodeGen/CGStmt.cpp
index c67d1d1b0da..21fb36a72d6 100644
--- a/clang/lib/CodeGen/CGStmt.cpp
+++ b/clang/lib/CodeGen/CGStmt.cpp
@@ -895,9 +895,14 @@ static CSFC_Result CollectStatementsForCase(const Stmt *S,
         case CSFC_Success:
           // A successful result means that either 1) that the statement doesn't
           // have the case and is skippable, or 2) does contain the case value
-          // and also contains the break to exit the switch.  In either case,
-          // we continue scanning the body of the compound statement to see if
-          // the rest are skippable or have the case.
+          // and also contains the break to exit the switch.  In the later case,
+          // we just verify the rest of the statements are elidable.
+          if (FoundCase) {
+            for (++I; I != E; ++I)
+              if (CodeGenFunction::ContainsLabel(*I, true))
+                return CSFC_Failure;
+            return CSFC_Success;
+          }
           break;
         case CSFC_FallThrough:
           // If we have a fallthrough condition, then we must have found the
diff --git a/clang/test/CodeGen/switch-dce.c b/clang/test/CodeGen/switch-dce.c
index 95c5e03633a..82b206149b9 100644
--- a/clang/test/CodeGen/switch-dce.c
+++ b/clang/test/CodeGen/switch-dce.c
@@ -167,7 +167,9 @@ void test9(int i) {
   } 
 }
 
-
+// CHECK: @test10
+// CHECK-NOT: switch
+// CHECK: ret i32
 int test10(void) {
 	switch(8) {
 		case 8:
@@ -180,3 +182,17 @@ int test10(void) {
 	
 	return 0;
 }
+
+// CHECK: @test11
+// CHECK-NOT: switch
+// CHECK: ret void
+void test11() {
+  switch (1) {
+    case 1:
+      break;
+    case 42: ;
+      int x;  // eliding var decl?
+      x = 4;
+      break;
+  }
+}