[llvm] r330079 - [WebAssembly] Fix a bug in MachineBasicBlock::findDebugLoc() call

[Heejin Ahn via llvm-commits]

It's hard to provide a test case that makes sense, because the failing
condition only happens when a basic block does not have a terminator but
branches to another BB that is not a layout successor (= a BB that comes
right after the current BB), which is not possible. I accidentally found
that bug while debugging my buggy and not-well-formed IR, which cannot be
generated from a valid ll file. The fix was very trivial, almost to the
extent of a typo fix, and the reviewer of that patch (yurydelendik@) was
who wrote that line of the code a month ago, so I thought he could make
sure it was correct. I CC'ed him here.

On Mon, Apr 16, 2018 at 9:41 AM David Blaikie <dblaikie at gmail.com> wrote:

> Test case?
>
> On Fri, Apr 13, 2018 at 5:15 PM Heejin Ahn via llvm-commits <
> llvm-commits at lists.llvm.org> wrote:
>
>> Author: aheejin
>> Date: Fri Apr 13 17:12:12 2018
>> New Revision: 330079
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=330079&view=rev
>> Log:
>> [WebAssembly] Fix a bug in MachineBasicBlock::findDebugLoc() call
>>
>> Summary:
>> InsertPos is within the bacic block `Header`, so `findDebugLoc()` should
>> be called on not `MBB` but `Header` instead.
>>
>> Reviewers: yurydelendik
>>
>> Subscribers: jfb, dschuff, aprantl, sbc100, jgravelle-google, sunfish,
>> JDevlieghere, llvm-commits
>>
>> Differential Revision: https://reviews.llvm.org/D45648
>>
>> Modified:
>>     llvm/trunk/lib/Target/WebAssembly/WebAssemblyCFGStackify.cpp
>>
>> Modified: llvm/trunk/lib/Target/WebAssembly/WebAssemblyCFGStackify.cpp
>> URL:
>> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/WebAssembly/WebAssemblyCFGStackify.cpp?rev=330079&r1=330078&r2=330079&view=diff
>>
>> ==============================================================================
>> --- llvm/trunk/lib/Target/WebAssembly/WebAssemblyCFGStackify.cpp
>> (original)
>> +++ llvm/trunk/lib/Target/WebAssembly/WebAssemblyCFGStackify.cpp Fri Apr
>> 13 17:12:12 2018
>> @@ -147,9 +147,10 @@ static void PlaceBlockMarker(
>>    }
>>
>>    // Add the BLOCK.
>> -  MachineInstr *Begin = BuildMI(*Header, InsertPos,
>> MBB.findDebugLoc(InsertPos),
>> -                                TII.get(WebAssembly::BLOCK))
>> -
>> .addImm(int64_t(WebAssembly::ExprType::Void));
>> +  MachineInstr *Begin =
>> +      BuildMI(*Header, InsertPos, Header->findDebugLoc(InsertPos),
>> +              TII.get(WebAssembly::BLOCK))
>> +          .addImm(int64_t(WebAssembly::ExprType::Void));
>>
>>    // Mark the end of the block.
>>    InsertPos = MBB.begin();
>>
>>
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>>
>
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