[PATCH] D149137: [Assignment Tracking] Check getTypeSizeInBits result for scalable vector types

[Orlando Cazalet-Hyams via Phabricator via llvm-commits]

Orlando created this revision.
Orlando added reviewers: jmorse, dmgreen.
Herald added a subscriber: hiraditya.
Herald added a project: All.
Orlando requested review of this revision.
Herald added subscribers: llvm-commits, alextsao1999.
Herald added a project: LLVM.

Without this patch, in `getAssignmentInfo` the result of `getTypeSizeInBits` is cast to `uint64_t`, which a) is an operation that will eventually be unsupported by the API according to the comments, and b) causes an assertion failure if the type is a scalable vector. Don't cast the `TypeSize` to `uint64_t` and check `isScalable` before getting the fixed size.

This can result in incorrect variable locations, see llvm.org/PR62346 (but is better than crashing).


https://reviews.llvm.org/D149137

Files:
  llvm/lib/IR/DebugInfo.cpp
  llvm/test/DebugInfo/assignment-tracking/AArch64/lit.local.cfg
  llvm/test/DebugInfo/assignment-tracking/AArch64/scalable-vectors.ll


Index: llvm/test/DebugInfo/assignment-tracking/AArch64/scalable-vectors.ll
===================================================================
--- /dev/null
+++ llvm/test/DebugInfo/assignment-tracking/AArch64/scalable-vectors.ll
@@ -0,0 +1,51 @@
+; RUN: llc %s -stop-after=finalize-isel -o - | FileCheck %s
+
+;; Hand written. Check AssignmentTrackingAnalysis doesn't try to get the size
+;; of scalable vectors (which causes an assertion failure).
+
+; CHECK: DBG_VALUE %stack.0, $noreg, ![[#]], !DIExpression(DW_OP_deref)
+; CHECK: DBG_VALUE i256 0, $noreg, ![[#]], !DIExpression()
+;; FIXME: We should reinstate (or poison) the variable at the store. See
+;; llvm.org/PR62346.
+
+target triple = "aarch64"
+
+define dso_local void @square(ptr %0) local_unnamed_addr #0 !dbg !9 {
+entry:
+   %1 = alloca <32 x i8>, !DIAssignID !18
+   call void @llvm.dbg.assign(metadata i1 poison, metadata !19, metadata !DIExpression(), metadata !18, metadata ptr %1, metadata !DIExpression()), !dbg !21
+   %2 = load <vscale x 8 x i8>, ptr %0, align 1
+   call void @llvm.dbg.assign(metadata i256 0, metadata !19, metadata !DIExpression(), metadata !22, metadata ptr %1, metadata !DIExpression()), !dbg !21
+   store <vscale x 8 x i8> %2, ptr %1, align 1
+   ret void
+}
+
+declare void @llvm.dbg.assign(metadata, metadata, metadata, metadata, metadata, metadata)
+
+attributes #0 = { vscale_range(1,16) "target-cpu"="generic" "target-features"="+sve" }
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!2, !3, !7}
+!llvm.ident = !{!8}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C11, file: !1, producer: "clang version 17.0.0", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, splitDebugInlining: false, nameTableKind: None)
+!1 = !DIFile(filename: "/app/example.c", directory: "/app")
+!2 = !{i32 7, !"Dwarf Version", i32 4}
+!3 = !{i32 2, !"Debug Info Version", i32 3}
+!7 = !{i32 7, !"debug-info-assignment-tracking", i1 true}
+!8 = !{!"clang version 17.0.0"}
+!9 = distinct !DISubprogram(name: "square", scope: !10, file: !10, line: 1, type: !11, scopeLine: 1, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !17)
+!10 = !DIFile(filename: "example.c", directory: "/app")
+!11 = !DISubroutineType(types: !12)
+!12 = !{null, !13, !14, !16}
+!13 = !DIDerivedType(tag: DW_TAG_restrict_type, baseType: !14)
+!14 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !15, size: 64)
+!15 = !DIBasicType(name: "unsigned char", size: 8, encoding: DW_ATE_unsigned_char)
+!16 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!17 = !{}
+!18 =  distinct !DIAssignID()
+!19 = !DILocalVariable(name: "i", scope: !9, file: !10, line: 2, type: !20)
+!20 = !DIBasicType(name: "cats", size: 256, encoding: DW_ATE_signed)
+!21 = !DILocation(line: 0, scope: !9)
+!22 =  distinct !DIAssignID()
+
Index: llvm/test/DebugInfo/assignment-tracking/AArch64/lit.local.cfg
===================================================================
--- /dev/null
+++ llvm/test/DebugInfo/assignment-tracking/AArch64/lit.local.cfg
@@ -0,0 +1,2 @@
+if not 'AArch64' in config.root.targets:
+    config.unsupported = True
Index: llvm/lib/IR/DebugInfo.cpp
===================================================================
--- llvm/lib/IR/DebugInfo.cpp
+++ llvm/lib/IR/DebugInfo.cpp
@@ -1944,17 +1944,22 @@
   return getAssignmentInfoImpl(DL, StoreDest, SizeInBits);
 }
 
+static std::optional<AssignmentInfo>
+getScalarAssignmentInfo(const DataLayout &DL, const Value *Dest, Type *StoredTy) {
+  TypeSize SizeInBits = DL.getTypeSizeInBits(StoredTy);
+  if (SizeInBits.isScalable())
+    return std::nullopt;
+  return getAssignmentInfoImpl(DL, Dest, SizeInBits.getFixedValue());
+}
+
 std::optional<AssignmentInfo> at::getAssignmentInfo(const DataLayout &DL,
                                                     const StoreInst *SI) {
-  const Value *StoreDest = SI->getPointerOperand();
-  uint64_t SizeInBits = DL.getTypeSizeInBits(SI->getValueOperand()->getType());
-  return getAssignmentInfoImpl(DL, StoreDest, SizeInBits);
+  return getScalarAssignmentInfo(DL, SI->getPointerOperand(), SI->getValueOperand()->getType());
 }
 
 std::optional<AssignmentInfo> at::getAssignmentInfo(const DataLayout &DL,
                                                     const AllocaInst *AI) {
-  uint64_t SizeInBits = DL.getTypeSizeInBits(AI->getAllocatedType());
-  return getAssignmentInfoImpl(DL, AI, SizeInBits);
+  return getScalarAssignmentInfo(DL, AI, AI->getAllocatedType());
 }
 
 /// Returns nullptr if the assignment shouldn't be attributed to this variable.


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