r211722 - PR20038: DebugInfo: Call sites without DebugLocs for temporary dtors after a conditional

[Reid Kleckner]

This test needs a triple, it's failing locally for me due to the
Itanium-style names (@_ZN1CD1Ev). -triple %itanium_abi_triple is the usual
fix.


On Wed, Jun 25, 2014 at 10:57 AM, David Blaikie <dblaikie at gmail.com> wrote:

> Author: dblaikie
> Date: Wed Jun 25 12:57:34 2014
> New Revision: 211722
>
> URL: http://llvm.org/viewvc/llvm-project?rev=211722&view=rev
> Log:
> PR20038: DebugInfo: Call sites without DebugLocs for temporary dtors after
> a conditional
>
> With && at the top level of an expression, the last thing done when
> emitting the expression was an unconditional jump to the cleanup block.
> To reduce the amount of stepping, the DebugLoc is omitted from the
> unconditional jump. This is done by clearing the IRBuilder's
> "CurrentDebugLocation"*. If this is not set to some non-empty value
> before the cleanup block is emitted, the cleanups don't get a location
> either. If a call without a location is emitted in a function with debug
> info, and that call is then inlined - bad things happen. (without a
> location for the call site, the inliner would just leave the inlined
> DebugLocs as they were - pointing to roots in the original function, not
> inlined into the current function)
>
> Follow up commit to LLVM will ensure that breaking the invariants of the
> DebugLoc chains by having chains that don't lead to the current function
> will fail assertions, so we shouldn't accidentally slip any of these
> cases in anymore. Those assertions may reveal further cases that need to
> be fixed in clang, though I've tried to test heavily to avoid that.
>
> * See r128471, r128513 for the code that clears the
>   CurrentDebugLocation. Simply removing this code or moving the code
>   into IRBuilder to apply to all unconditional branches would regress
>   desired behavior, unfortunately.
>
> Added:
>     cfe/trunk/test/CodeGenCXX/PR20038.cpp
> Modified:
>     cfe/trunk/lib/CodeGen/CGExprScalar.cpp
>
> Modified: cfe/trunk/lib/CodeGen/CGExprScalar.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CGExprScalar.cpp?rev=211722&r1=211721&r2=211722&view=diff
>
> ==============================================================================
> --- cfe/trunk/lib/CodeGen/CGExprScalar.cpp (original)
> +++ cfe/trunk/lib/CodeGen/CGExprScalar.cpp Wed Jun 25 12:57:34 2014
> @@ -358,7 +358,10 @@ public:
>    Value *VisitExprWithCleanups(ExprWithCleanups *E) {
>      CGF.enterFullExpression(E);
>      CodeGenFunction::RunCleanupsScope Scope(CGF);
> -    return Visit(E->getSubExpr());
> +    auto *V = Visit(E->getSubExpr());
> +    if (CGDebugInfo *DI = CGF.getDebugInfo())
> +      DI->EmitLocation(Builder, E->getLocEnd(), false);
> +    return V;
>    }
>    Value *VisitCXXNewExpr(const CXXNewExpr *E) {
>      return CGF.EmitCXXNewExpr(E);
>
> Added: cfe/trunk/test/CodeGenCXX/PR20038.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGenCXX/PR20038.cpp?rev=211722&view=auto
>
> ==============================================================================
> --- cfe/trunk/test/CodeGenCXX/PR20038.cpp (added)
> +++ cfe/trunk/test/CodeGenCXX/PR20038.cpp Wed Jun 25 12:57:34 2014
> @@ -0,0 +1,11 @@
> +// RUN: %clang_cc1 -g -emit-llvm %s -o - | FileCheck %s
> +
> +struct C {
> +  ~C();
> +};
> +extern bool b;
> +// CHECK: call void @_ZN1CD1Ev({{.*}}), !dbg [[DTOR_CALL_LOC:![0-9]*]]
> +// CHECK: [[FUN4:.*]] = {{.*}}; [ DW_TAG_subprogram ] {{.*}} [def] [fun4]
> +// CHECK: [[DTOR_CALL_LOC]] = metadata !{i32 [[@LINE+2]], i32 0, metadata
> [[FUN4_BLOCK:.*]], null}
> +// CHECK: [[FUN4_BLOCK]] = metadata !{{{[^,]*}}, {{[^,]*}}, metadata
> [[FUN4]],
> +void fun4() { b && (C(), 1); }
>
>
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