Add salvageDebugInfo support for ptrtoint / inttoptr with trunc/ext behavior

[aprantl]

Summary

This patch enables debug info salvaging for truncating/extending ptr int conversions. The testcase uncovered a bug in adce, which is addressed separately.

[myhsu]

This patch seems reasonable to me

llvm/lib/Transforms/Utils/Local.cpp

1924

(nit) Should we bail out if FromTypeBitSize and ToTypeBitSize are the same? Usually these two values are different for sext/zext/trunc but for inttoptr/ptrtoint it's pretty common that they have the same value.

[aprantl]

llvm/lib/Transforms/Utils/Local.cpp

1924

Interestingly, no! If the size is the same CI->isNoopCast(DL) will return true, even for ptrtoint/inttoptr.

[myhsu]

llvm/lib/Transforms/Utils/Local.cpp

1924

Ahh i see, good catch!

llvm/lib/Transforms/Utils/Local.cpp

Value *llvm::salvageDebugInfoImpl(Instruction &I, uint64_t CurrentLocOps,
   if (auto *CI = dyn_cast<CastInst>(&I)) {
     Value *FromValue = CI->getOperand(0);
     // No-op casts are irrelevant for debug info.
     if (CI->isNoopCast(DL)) {
       return FromValue;
     }
 
     Type *Type = CI->getType();
+    if (Type->isPointerTy())
+      Type = DL.getIntPtrType(Type);
     // Casts other than Trunc, SExt, or ZExt to scalar types cannot be salvaged.
     if (Type->isVectorTy() ||
-        !(isa<TruncInst>(&I) || isa<SExtInst>(&I) || isa<ZExtInst>(&I)))
+        !(isa<TruncInst>(&I) || isa<SExtInst>(&I) || isa<ZExtInst>(&I) ||
+          isa<IntToPtrInst>(&I) || isa<PtrToIntInst>(&I)))
       return nullptr;
 
-    unsigned FromTypeBitSize = FromValue->getType()->getScalarSizeInBits();
+    llvm::Type *FromType = FromValue->getType();
+    if (FromType->isPointerTy())
+      FromType = DL.getIntPtrType(FromType);
+
+    unsigned FromTypeBitSize = FromType->getScalarSizeInBits();
     unsigned ToTypeBitSize = Type->getScalarSizeInBits();
 
     auto ExtOps = DIExpression::getExtOps(FromTypeBitSize, ToTypeBitSize,
                                           isa<SExtInst>(&I));
     Ops.append(ExtOps.begin(), ExtOps.end());
     return FromValue;
   }
 
   if (auto *GEP = dyn_cast<GetElementPtrInst>(&I))
     return getSalvageOpsForGEP(GEP, DL, CurrentLocOps, Ops, AdditionalValues);
-  else if (auto *BI = dyn_cast<BinaryOperator>(&I)) {
+  if (auto *BI = dyn_cast<BinaryOperator>(&I))
     return getSalvageOpsForBinOp(BI, CurrentLocOps, Ops, AdditionalValues);
-  }
+
   // *Not* to do: we should not attempt to salvage load instructions,
   // because the validity and lifetime of a dbg.value containing
   // DW_OP_deref becomes difficult to analyze. See PR40628 for examples.
   return nullptr;
 }
 
 /// A replacement for a dbg.value expression.
 using DbgValReplacement = Optional<DIExpression *>;

llvm/test/Transforms/Util/salvage-debuginfo.ll

+; RUN: opt -adce %s -S -o - | FileCheck %s
+target datalayout = "e-m:o-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-apple-macosx"
+define void @f(i32) !dbg !8 {
+entry:
+  %p_x = inttoptr i32 %0 to i8*
+  %i_x = ptrtoint i8* %p_x to i32
+  ; CHECK: call void @llvm.dbg.value(metadata i8* undef,
+  ; CHECK-SAME: !DIExpression(DW_OP_LLVM_convert, 64, DW_ATE_unsigned,
+  ; CHECK-SAME:               DW_OP_LLVM_convert, 32, DW_ATE_unsigned, DW_OP_stack_value))
+  call void @llvm.dbg.value(metadata i32 %i_x, metadata !11, metadata !DIExpression()), !dbg !13
+  ret void, !dbg !13
+}
+declare void @llvm.dbg.value(metadata, metadata, metadata)
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!3, !4}
+!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, emissionKind: FullDebug)
+!1 = !DIFile(filename: "salavage.c", directory: "/")
+!3 = !{i32 2, !"Dwarf Version", i32 4}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!8 = distinct !DISubprogram(name: "f", scope: !1, file: !1, line: 1, type: !9, isLocal: false, isDefinition: true, scopeLine: 1, isOptimized: false, unit: !0)
+!9 = !DISubroutineType(types: !10)
+!10 = !{null}
+!11 = !DILocalVariable(name: "x", scope: !8, file: !1, line: 2, type: !12)
+!12 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!13 = !DILocation(line: 1, column: 1, scope: !8)