[PATCH] D107784: Fix SEH and IP2State table addresses for Windows

[Reid Kleckner via Phabricator via llvm-commits]

rnk requested changes to this revision.
rnk added inline comments.
This revision now requires changes to proceed.


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Comment at: llvm/lib/CodeGen/AsmPrinter/WinException.cpp:336
-                                   Asm->OutContext);
-  return MCBinaryExpr::createAdd(create32bitRef(Label),
-                                 MCConstantExpr::create(1, Asm->OutContext),
----------------
It seems that after several rounds of refactoring, there are no comments here explaining why this happens. :(


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Comment at: llvm/lib/CodeGen/AsmPrinter/WinException.cpp:661
     AddComment("LabelStart");
     OS.emitValue(getLabel(BeginLabel), 4);
     AddComment("LabelEnd");
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Arguably, this is the special case that opens a range but does not end one, so the modification would be here.


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Comment at: llvm/lib/CodeGen/AsmPrinter/WinException.cpp:955
       IPToStateTable.push_back(
           std::make_pair(getLabel(ChangeLabel), StateChange.NewState));
       // FIXME: assert that NewState is between CatchLow and CatchHigh.
----------------
This is the other call site of getLabel for C++.


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Comment at: llvm/test/CodeGen/WinEH/wineh-noret-cleanup.ll:49
 ; CXX-NEXT:   .long   -1
-; CXX-NEXT:   .long   .Ltmp0 at IMGREL+1
+; CXX-NEXT:   .long   .Ltmp0 at IMGREL
 ; CXX-NEXT:   .long   1
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These changes are incorrect. The C++ ip2state table doesn't have a begin/end pair, it has a series of labels. When an exception is thrown from the last instruction in a range, these labels must be strictly greater than the return address.

Fortunately, there are no single-byte instructions that can throw a C++ exception, so the entire table can be biased forwards by one byte.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D107784/new/

https://reviews.llvm.org/D107784