r207480 - Debug info: Improve line table for functions with cleanups an early exit

[Richard Smith]

On Mon, Apr 28, 2014 at 6:08 PM, Adrian Prantl <aprantl at apple.com> wrote:

> Author: adrian
> Date: Mon Apr 28 20:07:59 2014
> New Revision: 207480
>
> URL: http://llvm.org/viewvc/llvm-project?rev=207480&view=rev
> Log:
> Debug info: Improve line table for functions with cleanups an early exit
> and no return expr at the end of the function.
> The "function has only simple returns" check in FinishFunction tests
> whether the number of simple return exprs equals the number of return
> exprs, but so far a fallthrough at the end of a function was not counted
> as a return, which would result in cleanup code being associated with the
> wrong source line.
>
> rdar://problem/16733984.
>
> Modified:
>     cfe/trunk/lib/CodeGen/CodeGenFunction.cpp
>     cfe/trunk/test/CodeGenObjC/arc-linetable.m
>
> Modified: cfe/trunk/lib/CodeGen/CodeGenFunction.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CodeGenFunction.cpp?rev=207480&r1=207479&r2=207480&view=diff
>
> ==============================================================================
> --- cfe/trunk/lib/CodeGen/CodeGenFunction.cpp (original)
> +++ cfe/trunk/lib/CodeGen/CodeGenFunction.cpp Mon Apr 28 20:07:59 2014
> @@ -498,6 +498,22 @@ void CodeGenFunction::EmitOpenCLKernelMe
>    OpenCLKernelMetadata->addOperand(kernelMDNode);
>  }
>
> +/// Determine whether the function F ends with a return stmt.
> +static bool endsWithReturn(const Decl* F) {
> +  const Stmt *Body = nullptr;
> +  if (auto *FD = dyn_cast_or_null<FunctionDecl>(F))
> +    Body = FD->getBody();
> +  else if (auto *OMD = dyn_cast_or_null<ObjCMethodDecl>(F))
> +    Body = OMD->getBody();
> +
> +  if (auto *CS = dyn_cast_or_null<CompoundStmt>(Body)) {
> +    auto LastStmt = CS->body_rbegin();
> +    if (LastStmt != CS->body_rend())
> +      return isa<ReturnStmt>(*LastStmt);
> +  }
> +  return false;
> +}
> +
>  void CodeGenFunction::StartFunction(GlobalDecl GD,
>                                      QualType RetTy,
>                                      llvm::Function *Fn,
> @@ -593,6 +609,10 @@ void CodeGenFunction::StartFunction(Glob
>    if (RetTy->isVoidType()) {
>      // Void type; nothing to return.
>      ReturnValue = 0;
> +
> +    // Count the implicit return.
> +    if (!endsWithReturn(D))
> +      ++NumReturnExprs;
>    } else if (CurFnInfo->getReturnInfo().getKind() == ABIArgInfo::Indirect
> &&
>               !hasScalarEvaluationKind(CurFnInfo->getReturnType())) {
>      // Indirect aggregate return; emit returned value directly into sret
> slot.
>
> Modified: cfe/trunk/test/CodeGenObjC/arc-linetable.m
> URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGenObjC/arc-linetable.m?rev=207480&r1=207479&r2=207480&view=diff
>
> ==============================================================================
> --- cfe/trunk/test/CodeGenObjC/arc-linetable.m (original)
> +++ cfe/trunk/test/CodeGenObjC/arc-linetable.m Mon Apr 28 20:07:59 2014
> @@ -32,6 +32,15 @@
>  // CHECK: @objc_msgSend{{.*}} !dbg ![[MSG7:[0-9]+]]
>  // CHECK: ret {{.*}} !dbg ![[RET7:[0-9]+]]
>
> +// CHECK: define {{.*}}testCleanupVoid
> +// CHECK: icmp ne {{.*}}!dbg ![[SKIP1:[0-9]+]]
> +// CHECK-NEXT: br {{.*}}, label %[[CLEANUP:.*]], label
> +// CHECK: [[CLEANUP]]:
>

This will fail on any non-Asserts clang (where we don't emit label names in
the IR). Please fix or revert!


> +// CHECK-NEXT: !dbg ![[RET8:[0-9]+]]
> +// CHECK: @objc_storeStrong{{.*}}, !dbg ![[ARC8:[0-9]+]]
> +// CHECK: ret {{.*}} !dbg ![[RET8]]
> +
> +typedef signed char BOOL;
>
>  @interface NSObject
>  + (id)alloc;
> @@ -93,6 +102,22 @@
>    return 1;
>  }
>
> +- (void)testCleanupVoid:(BOOL)skip withDelegate: (AppDelegate *) delegate
> {
> +  static BOOL skip_all;
> +  // CHECK: ![[SKIP1]] = metadata !{i32 [[@LINE+1]], i32 0,
> +  if (!skip_all) {
> +    if (!skip) {
> +      return;
> +    }
> +    NSString *s = @"bar";
> +    if (!skip) {
> +      [delegate testVoid :s];
> +    }
> +  }
> +  // CHECK: ![[RET8]] = metadata !{i32 [[@LINE+2]], i32 0,
> +  // CHECK: ![[ARC8]] = metadata !{i32 [[@LINE+1]], i32 0,
> +}
> +
>
>  @end
>
>
>
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