7dc9d73731
When working out which instruction defines a value, the instruction-referencing variable location code has a few special cases for physical registers: * Arguments are never defined by instructions, * Constant physical registers always read the same value, are never def'd This patch adds a third case for the llvm.frameaddress intrinsics: you can read the framepointer in any block if you so choose, and use it as a variable location, as shown in the added test. This rather violates one of the assumptions behind instruction referencing, that LLVM-ir shouldn't be able to read from an arbitrary register at some arbitrary point in the program. The solution for now is to just emit a DBG_PHI that reads the register value: this works, but if we wanted to do something clever with DBG_PHIs in the future then this would probably get in the way. As it stands, this patch avoids a crash. Differential Revision: https://reviews.llvm.org/D106659
43 lines
1.8 KiB
LLVM
43 lines
1.8 KiB
LLVM
; RUN: llc %s -o - -start-after=codegenprepare -stop-before=finalize-isel \
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; RUN: -mtriple=x86_64-unknown-unknown -experimental-debug-variable-locations \
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; RUN: | FileCheck %s
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; Test for a crash / weird behaviour when llvm.frameaddress.* is called.
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; Today, as a concession, we emit a DBG_PHI allowing the frame register value
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; to be read, but it could be expressed in other ways. Check that this works
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; outside of the entry block, to avoid the frame register being recognised
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; as def'd by frame-setup code or as a function argument.
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; CHECK-LABEL: bb.1.notentry:
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; CHECK: DBG_PHI $rbp
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declare void @llvm.dbg.value(metadata, metadata, metadata)
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declare i8 *@llvm.frameaddress.p0i8(i32)
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; Function Attrs: mustprogress nofree nosync nounwind sspstrong uwtable
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define hidden i8 * @foo() !dbg !7 {
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entry:
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br label %notentry
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notentry:
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%0 = tail call i8* @llvm.frameaddress.p0i8(i32 0), !dbg !12
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call void @llvm.dbg.value(metadata i8* %0, metadata !11, metadata !DIExpression()), !dbg !12
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ret i8 *%0
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}
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!llvm.dbg.cu = !{!0}
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!llvm.module.flags = !{!3, !4, !5, !6}
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!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !1, producer: "", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug)
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!1 = !DIFile(filename: "foo.cpp", directory: ".")
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!2 = !DIBasicType(name: "int", size: 8, encoding: DW_ATE_signed)
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!3 = !{i32 2, !"Dwarf Version", i32 4}
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!4 = !{i32 2, !"Debug Info Version", i32 3}
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!5 = !{i32 1, !"wchar_size", i32 2}
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!6 = !{i32 7, !"PIC Level", i32 2}
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!7 = distinct !DISubprogram(name: "foo", linkageName: "foo", scope: !1, file: !1, line: 6, type: !8, scopeLine: 6, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !10)
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!8 = !DISubroutineType(types: !9)
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!9 = !{!2, !2}
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!10 = !{!11}
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!11 = !DILocalVariable(name: "baz", scope: !7, file: !1, line: 7, type: !2)
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!12 = !DILocation(line: 10, scope: !7)
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