[llvm] r296488 - Strip debug info when inlining into a nodebug function.
David Blaikie via llvm-commits
llvm-commits at lists.llvm.org
Mon Mar 6 14:42:47 PST 2017
Might need to revert and discuss this further.
When I implemented the infamous assert many years ago I hit cases like this
and specifically crafted the assert to work around/allow situations like
this because they came up in reality:
void f1();
inline __attribute__((alwaysinline)) void f2() {
f1();
}
inline __attribute__((alwaysinline)) __attribute__((nodebug)) void f3() {
f2();
}
void f4() {
f3();
}
Even in this case, there's value in keeping the deubg info in f3 after f2
is inlined into it so that when examining f4 there's inline info about f2.
It ends up appearing as though f3 were never there - but f2 and f4 were
totally there/meaningful/etc.
Another reason/way to look at this is consistency: If the nodebug function
were inlined first, then f2 was inlined - it would produce debug info for
f2 and f4. It would be weird if the order of inlining produced
substantially different debug info like this.
If I'm understanding all this correctly...
On Tue, Feb 28, 2017 at 9:09 AM Adrian Prantl via llvm-commits <
llvm-commits at lists.llvm.org> wrote:
> Author: adrian
> Date: Tue Feb 28 10:58:13 2017
> New Revision: 296488
>
> URL: http://llvm.org/viewvc/llvm-project?rev=296488&view=rev
> Log:
> Strip debug info when inlining into a nodebug function.
>
> The LLVM backend cannot produce any debug info for an llvm::Function
> without a DISubprogram attachment. When inlining a debug-info-carrying
> function into a nodebug function, there is therefore no reason to keep
> any debug info intrinsic calls or debug locations on the instructions.
>
> This fixes a problem discovered in PR32042.
>
> rdar://problem/30679307
>
> Added:
> llvm/trunk/test/Transforms/Inline/nodebug.ll
> Modified:
> llvm/trunk/lib/Transforms/Utils/InlineFunction.cpp
> llvm/trunk/test/Transforms/Inline/local-as-metadata-undominated-use.ll
>
> Modified: llvm/trunk/lib/Transforms/Utils/InlineFunction.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/InlineFunction.cpp?rev=296488&r1=296487&r2=296488&view=diff
>
> ==============================================================================
> --- llvm/trunk/lib/Transforms/Utils/InlineFunction.cpp (original)
> +++ llvm/trunk/lib/Transforms/Utils/InlineFunction.cpp Tue Feb 28 10:58:13
> 2017
> @@ -1343,22 +1343,26 @@ static bool allocaWouldBeStaticInEntry(c
> return isa<Constant>(AI->getArraySize()) && !AI->isUsedWithInAlloca();
> }
>
> -/// Update inlined instructions' line numbers to
> -/// to encode location where these instructions are inlined.
> -static void fixupLineNumbers(Function *Fn, Function::iterator FI,
> - Instruction *TheCall, bool
> CalleeHasDebugInfo) {
> +/// Update inlined instructions' line numbers to to encode location where
> these
> +/// instructions are inlined. Also strip all debug intrinsics that were
> inlined
> +/// into a nodebug function; there is no debug info the backend could
> produce
> +/// for a function without a DISubprogram attachment.
> +static void fixupDebugInfo(Function *Fn, Function::iterator FI,
> + Instruction *TheCall, bool CalleeHasDebugInfo)
> {
> + bool CallerHasDebugInfo = Fn->getSubprogram();
> + bool StripDebugInfo = !CallerHasDebugInfo && CalleeHasDebugInfo;
> + SmallVector<DbgInfoIntrinsic *, 8> IntrinsicsToErase;
> const DebugLoc &TheCallDL = TheCall->getDebugLoc();
> - if (!TheCallDL)
> - return;
>
> auto &Ctx = Fn->getContext();
> - DILocation *InlinedAtNode = TheCallDL;
> + DILocation *InlinedAtNode = nullptr;
>
> // Create a unique call site, not to be confused with any other call
> from the
> // same location.
> - InlinedAtNode = DILocation::getDistinct(
> - Ctx, InlinedAtNode->getLine(), InlinedAtNode->getColumn(),
> - InlinedAtNode->getScope(), InlinedAtNode->getInlinedAt());
> + if (TheCallDL)
> + InlinedAtNode = DILocation::getDistinct(
> + Ctx, TheCallDL->getLine(), TheCallDL->getColumn(),
> + TheCallDL->getScope(), TheCallDL->getInlinedAt());
>
> // Cache the inlined-at nodes as they're built so they are reused,
> without
> // this every instruction's inlined-at chain would become distinct from
> each
> @@ -1368,6 +1372,17 @@ static void fixupLineNumbers(Function *F
> for (; FI != Fn->end(); ++FI) {
> for (BasicBlock::iterator BI = FI->begin(), BE = FI->end();
> BI != BE; ++BI) {
> + if (StripDebugInfo) {
> + // Inlining into a nodebug function.
> + if (auto *DI = dyn_cast<DbgInfoIntrinsic>(BI))
> + // Mark dead debug intrinsics for deletion.
> + IntrinsicsToErase.push_back(DI);
> + else
> + // Remove the dangling debug location.
> + BI->setDebugLoc(DebugLoc());
> + continue;
> + }
> +
> if (DebugLoc DL = BI->getDebugLoc()) {
> BI->setDebugLoc(
> updateInlinedAtInfo(DL, InlinedAtNode, BI->getContext(),
> IANodes));
> @@ -1390,6 +1405,9 @@ static void fixupLineNumbers(Function *F
> BI->setDebugLoc(TheCallDL);
> }
> }
> +
> + for (auto *DI : IntrinsicsToErase)
> + DI->eraseFromParent();
> }
> /// Update the block frequencies of the caller after a callee has been
> inlined.
> ///
> @@ -1710,8 +1728,8 @@ bool llvm::InlineFunction(CallSite CS, I
> // For 'nodebug' functions, the associated DISubprogram is always
> null.
> // Conservatively avoid propagating the callsite debug location to
> // instructions inlined from a function whose DISubprogram is not
> null.
> - fixupLineNumbers(Caller, FirstNewBlock, TheCall,
> - CalledFunc->getSubprogram() != nullptr);
> + fixupDebugInfo(Caller, FirstNewBlock, TheCall,
> + CalledFunc->getSubprogram() != nullptr);
>
> // Clone existing noalias metadata if necessary.
> CloneAliasScopeMetadata(CS, VMap);
>
> Modified:
> llvm/trunk/test/Transforms/Inline/local-as-metadata-undominated-use.ll
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/Inline/local-as-metadata-undominated-use.ll?rev=296488&r1=296487&r2=296488&view=diff
>
> ==============================================================================
> --- llvm/trunk/test/Transforms/Inline/local-as-metadata-undominated-use.ll
> (original)
> +++ llvm/trunk/test/Transforms/Inline/local-as-metadata-undominated-use.ll
> Tue Feb 28 10:58:13 2017
> @@ -16,14 +16,14 @@ entry:
> }
>
> ; CHECK-LABEL: define i32 @caller(
> -define i32 @caller(i32 %i) {
> +define i32 @caller(i32 %i) !dbg !3 {
> ; CHECK-NEXT: entry:
> entry:
> ; Although the inliner shouldn't crash, it can't be expected to get the
> ; "correct" SSA value since its assumptions have been violated.
> ; CHECK-NEXT: tail call void @llvm.dbg.value(metadata ![[EMPTY:[0-9]+]],
> ; CHECK-NEXT: %{{.*}} = add nsw
> - %call = tail call i32 @foo(i32 %i)
> + %call = tail call i32 @foo(i32 %i), !dbg !14
> ret i32 %call
> }
>
> @@ -34,9 +34,9 @@ declare void @llvm.dbg.value(metadata, i
>
> !0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer:
> "clang version 3.9.0 (trunk 265634) (llvm/trunk 265637)", isOptimized:
> true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2)
> !1 = !DIFile(filename: "t.c", directory: "/path/to/tests")
> -
> ; CHECK: ![[EMPTY]] = !{}
> !2 = !{}
> +!3 = distinct !DISubprogram(name: "caller", scope: !1, file: !1, line: 3,
> type: !5, isLocal: false, isDefinition: true, scopeLine: 3, flags:
> DIFlagPrototyped, isOptimized: true, unit: !0)
> !4 = distinct !DISubprogram(name: "foo", scope: !1, file: !1, line: 2,
> type: !5, isLocal: false, isDefinition: true, scopeLine: 2, flags:
> DIFlagPrototyped, isOptimized: true, unit: !0)
> !5 = !DISubroutineType(types: !6)
> !6 = !{!7, !7}
> @@ -47,3 +47,4 @@ declare void @llvm.dbg.value(metadata, i
> !11 = !DILocation(line: 2, column: 13, scope: !4)
> !12 = !DILocation(line: 2, column: 27, scope: !4)
> !13 = !DILocation(line: 2, column: 18, scope: !4)
> +!14 = !DILocation(line: 3, scope: !3)
>
> Added: llvm/trunk/test/Transforms/Inline/nodebug.ll
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/Inline/nodebug.ll?rev=296488&view=auto
>
> ==============================================================================
> --- llvm/trunk/test/Transforms/Inline/nodebug.ll (added)
> +++ llvm/trunk/test/Transforms/Inline/nodebug.ll Tue Feb 28 10:58:13 2017
> @@ -0,0 +1,36 @@
> +; RUN: opt -inline -S -o - < %s | FileCheck %s
> +; Check that debug info is stripped when inlining into a nodebug function.
> +
> +declare void @llvm.dbg.declare(metadata, metadata, metadata)
> +declare void @llvm.dbg.value(metadata, i64, metadata, metadata)
> +
> +define void @foo() !dbg !2 {
> +entry:
> + %a = alloca i32
> + call void @llvm.dbg.value(metadata i32 0, i64 0, metadata !3, metadata
> !DIExpression()), !dbg !6
> + store i32 0, i32* %a, !dbg !6
> + ret void, !dbg !6
> +}
> +
> +; CHECK: define void @bar()
> +define void @bar() {
> +; CHECK-NEXT: entry
> +entry:
> +; CHECK-NEXT: alloca i32
> +; CHECK-NOT: dbg
> +; CHECK: ret void
> + call void @foo()
> + ret void
> +}
> +
> +!llvm.dbg.cu = !{!0}
> +!llvm.module.flags = !{!7, !8}
> +
> +!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer:
> "clang", emissionKind: FullDebug)
> +!1 = !DIFile(filename: "x.c", directory: "/")
> +!2 = distinct !DISubprogram(name: "foo", scope: !0, isDefinition: true,
> unit: !0)
> +!3 = !DILocalVariable(name: "a", arg: 1, scope: !2, file: !1, line: 1,
> type: !5)
> +!5 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
> +!6 = !DILocation(line: 1, scope: !2)
> +!7 = !{i32 2, !"Dwarf Version", i32 4}
> +!8 = !{i32 1, !"Debug Info Version", i32 3}
>
>
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