[SelectionDAG] Handle IntToPtr constants in dbg.value

[fdeazeve]

Summary

The function handleDebugValue has custom logic to handle certain kinds
constants, namely integers, floats and null pointers. However, it does
not handle constant pointers created from IntToPtr ConstantExpressions.
This patch addresses the issue by replacing the Constant with its
integer operand.

A similar bug was addressed for GlobalISel in D130642.

[fdeazeve]

I based the test on llvm/test/CodeGen/AArch64/fastisel-debugvalue-undef.ll, as I couldn't find a more generic test that was looking for these constants in dbg.value intrinsics.

[aprantl]

llvm/test/CodeGen/AArch64/inttoptr_debug_value.ll

2

does this also work with llc -O0

[fdeazeve]

llvm/test/CodeGen/AArch64/inttoptr_debug_value.ll

2

With O0, we default to global isel, and we have fixed the bug there.
I couldn't find a way to force selection dag with O0, there doesn't seem to be any llc flags for that.

[fdeazeve]

Rebased

llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp

bool SelectionDAGBuilder::handleDebugValue(ArrayRef<const Value *> Values,
   for (const Value *V : Values) {
     // Constant value.
     if (isa<ConstantInt>(V) || isa<ConstantFP>(V) || isa<UndefValue>(V) ||
         isa<ConstantPointerNull>(V)) {
       LocationOps.emplace_back(SDDbgOperand::fromConst(V));
       continue;
     }
 
+    // Look through IntToPtr constants.
+    if (auto *CE = dyn_cast<ConstantExpr>(V))
+      if (CE->getOpcode() == Instruction::IntToPtr) {
+        LocationOps.emplace_back(SDDbgOperand::fromConst(CE->getOperand(0)));
+        continue;
+      }
+
     // If the Value is a frame index, we can create a FrameIndex debug value
     // without relying on the DAG at all.
     if (const AllocaInst *AI = dyn_cast<AllocaInst>(V)) {
       auto SI = FuncInfo.StaticAllocaMap.find(AI);
       if (SI != FuncInfo.StaticAllocaMap.end()) {
         LocationOps.emplace_back(SDDbgOperand::fromFrameIdx(SI->second));
         continue;
       }

llvm/test/CodeGen/AArch64/inttoptr_debug_value.ll

+; RUN: llc -o - --print-after-isel %s 2>&1 | FileCheck %s
+
+target triple = "arm64-apple-ios13.4.0"
+define void @foo() !dbg !6 {
+  ; CHECK: DBG_VALUE 42, $noreg, !"myvar", !DIExpression()
+  call void @llvm.dbg.value(metadata ptr inttoptr (i64 42 to ptr), metadata !9, metadata !DIExpression()), !dbg !11
+  ret void
+}
+
+declare void @llvm.dbg.value(metadata, metadata, metadata)
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!5}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C, file: !1, producer: "debugify", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2)
+!1 = !DIFile(filename: "t.ll", directory: "/")
+!2 = !{}
+!5 = !{i32 4, !"Debug Info Version", i32 3}
+!6 = distinct !DISubprogram(name: "foo", linkageName: "foo", scope: null, file: !1, line: 1, type: !7, scopeLine: 1, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !8)
+!7 = !DISubroutineType(types: !2)
+!8 = !{!9}
+!9 = !DILocalVariable(name: "myvar", scope: !6, file: !1, line: 1, type: !10)
+!10 = !DIBasicType(name: "ty64", size: 64, encoding: DW_ATE_unsigned)
+!11 = !DILocation(line: 1, column: 1, scope: !6)
+!12 = !DILocation(line: 2, column: 1, scope: !6)