r276350 - [CodeGen] Fix a crash when constant folding switch statement

[Hans Wennborg via cfe-commits]

Richard: should we merge this to 3.9?

On Thu, Jul 21, 2016 at 6:31 PM, Erik Pilkington via cfe-commits
<cfe-commits at lists.llvm.org> wrote:
> Author: epilk
> Date: Thu Jul 21 17:31:40 2016
> New Revision: 276350
>
> URL: http://llvm.org/viewvc/llvm-project?rev=276350&view=rev
> Log:
> [CodeGen] Fix a crash when constant folding switch statement
>
> Differential revision: https://reviews.llvm.org/D22542
>
> Modified:
>     cfe/trunk/lib/CodeGen/CGStmt.cpp
>     cfe/trunk/test/CodeGenCXX/switch-case-folding-2.cpp
>
> Modified: cfe/trunk/lib/CodeGen/CGStmt.cpp
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CGStmt.cpp?rev=276350&r1=276349&r2=276350&view=diff
> ==============================================================================
> --- cfe/trunk/lib/CodeGen/CGStmt.cpp (original)
> +++ cfe/trunk/lib/CodeGen/CGStmt.cpp Thu Jul 21 17:31:40 2016
> @@ -1264,6 +1264,14 @@ void CodeGenFunction::EmitCaseStmt(const
>  }
>
>  void CodeGenFunction::EmitDefaultStmt(const DefaultStmt &S) {
> +  // If there is no enclosing switch instance that we're aware of, then this
> +  // default statement can be elided. This situation only happens when we've
> +  // constant-folded the switch.
> +  if (!SwitchInsn) {
> +    EmitStmt(S.getSubStmt());
> +    return;
> +  }
> +
>    llvm::BasicBlock *DefaultBlock = SwitchInsn->getDefaultDest();
>    assert(DefaultBlock->empty() &&
>           "EmitDefaultStmt: Default block already defined?");
>
> Modified: cfe/trunk/test/CodeGenCXX/switch-case-folding-2.cpp
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGenCXX/switch-case-folding-2.cpp?rev=276350&r1=276349&r2=276350&view=diff
> ==============================================================================
> --- cfe/trunk/test/CodeGenCXX/switch-case-folding-2.cpp (original)
> +++ cfe/trunk/test/CodeGenCXX/switch-case-folding-2.cpp Thu Jul 21 17:31:40 2016
> @@ -18,4 +18,13 @@ int main(void) {
>   return test(5);
>  }
>
> +void other_test() {
> +  switch(0) {
> +  case 0:
> +    do {
> +    default:;
> +    } while(0);
> +  }
> +}
> +
>  // CHECK: call i32 (i8*, ...) @_Z6printfPKcz
>
>
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