[DebugInfo] Prevent salvaged debug vars from being marked artificial #38942
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@swift-ci please test |
| @@ -2542,6 +2542,17 @@ void IRGenDebugInfoImpl::emitDbgIntrinsic( | |||
| !llvm::FindDbgDeclareUses(Storage).empty()) | |||
| return; | |||
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| // Fragment DIExpression cannot cover the whole variable | |||
| // or going out-of-bound. | |||
| if (auto Fragment = Expr->getFragmentInfo()) | |||
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Do we understand why we generate a fragment that covers the entire variable? Does this happen because we SROA a struct with a single member? Could we catch that case in IRGenDebugInfoImpl::emitVariableDeclaration() and not emit a DW_OP_LLVM_fragment?
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Yes this only happens when the struct only has one member. Originally I was going to solve this by preserving the bail out logic here and avoid emitting DW_OP_LLVM_fragment some place earlier as suggested. But then I found that it will be easier to just drop the fragment part here.
We were using compiler-generated source location (i.e. line number 0) on `debug_value` instructions were emitted by salvage debug info. But it turned out that IRGen will attach DW_AT_artificial on the associated debug variables, which are hidden in debugger by default. This patch prevent this issue by using the source location from the just-deleted instruction for these `debug_value` instructions. This indirectly triggered another bug where some of the LLVM !DIExpression-s we generated are actually invalid -- more specifically, the fragment inside is covering the whole debug variable. The reason it was not previously caught is because LLVM verifier skips any debug variable that is marked artificial, and all debug variables that have illegal fragment are falling under this category. Thus, this patch also fixes this issue by not generating the DW_OP_LLVM_fragment part if it's illegal.
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@swift-ci please test |
adrian-prantl
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Aug 19, 2021
| @@ -2542,6 +2542,17 @@ void IRGenDebugInfoImpl::emitDbgIntrinsic( | |||
| !llvm::FindDbgDeclareUses(Storage).empty()) | |||
| return; | |||
|
|
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| // Fragment DIExpression cannot cover the whole variable | |||
| // or going out-of-bound. | |||
| if (auto Fragment = Expr->getFragmentInfo()) | |||
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@swift-ci please test |
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@swift-ci test windows |
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We were using compiler-generated source location (i.e. line number
0) on
debug_valueinstructions that were emitted by salvage debug info.But it turned out that IRGen will attach DW_AT_artificial on the
associated debug variables, which are hidden in debugger by default.
This patch prevent this issue by using the source location from the
just-deleted instruction for these
debug_valueinstructions.This indirectly triggered another bug where some of the LLVM
!DIExpression-s we generated were actually invalid -- more specifically,
the enclosed fragment is covering the whole debug variable. The reason it was
not previously caught is because LLVM verifier skips any debug variable
that is marked artificial, and all debug variables that have illegal fragment
are falling under this category. This patch fixes this issue
by not generating any
llvm.dbg.valuewith illegal fragment.