[Coroutines] Add DW_OP_deref for transformed dbg.value intrinsic.

[junparser]

Summary

This patch adds DW_OP_deref for dbg.value intrinsic as @jmorse's suggestion in D90772 which allows debugger prints the value of variable instead of address.

Test Plan: check-llvm cppcoro

[bruno]

Thanks for following up with this, I did miss to incorporate this suggestion! Out of curiosity, are you using lldb or gdb to print the variable? In lldb I already get values instead of address before this patch, so I wonder if one debugger needs more specific info than the other.

[junparser]

In D92462#2428824, @bruno wrote:

Thanks for following up with this, I did miss to incorporate this suggestion! Out of curiosity, are you using lldb or gdb to print the variable? In lldb I already get values instead of address before this patch, so I wonder if one debugger needs more specific info than the other.

Hmm... I'm using trunk lldb and gdb8.2, both of them can only print address. Btw, os is centos7.2, FYI.

[bruno]

Hmm... I'm using trunk lldb and gdb8.2, both of them can only print address. Btw, os is centos7.2, FYI.

Interesting, I'm using an older version shipped with xcode+macOS, that might explain it. ToT is the way to go anyways, LGTM.

llvm/lib/Transforms/Coroutines/CoroFrame.cpp

for (Instruction *I : UsersToUpdate) {
 
       // These instructions are all dominated by the alloca, insert the
       // dbg.value in the beginning of the BB to enhance debugging
       // experience and allow values to be inspected as early as possible.
       // Prefer dbg.value over dbg.declare since it better sets expectations
       // that control flow can be later changed by other passes.
       auto *DI = cast<DbgDeclareInst>(FirstDbgDecl);
       BasicBlock *CurrentBlock = I->getParent();
-      DIB.insertDbgValueIntrinsic(G, DI->getVariable(), DI->getExpression(),
+      auto *DerefExpr =
+          DIExpression::append(DI->getExpression(), dwarf::DW_OP_deref);
+      DIB.insertDbgValueIntrinsic(G, DI->getVariable(), DerefExpr,
                                   DI->getDebugLoc(),
                                   &*CurrentBlock->getFirstInsertionPt());
       SeenDbgBBs.insert(CurrentBlock);
     }
   }
   Builder.SetInsertPoint(FramePtr->getNextNode());
   for (const auto &A : FrameData.Allocas) {
     AllocaInst *Alloca = A.Alloca;

llvm/test/Transforms/Coroutines/coro-debug-frame-variable.ll

 ; CHECK:       entry:
 ; CHECK:         %j = alloca i32, align 4
 ; CHECK:         [[IGEP:%.+]] = getelementptr inbounds %f.Frame, %f.Frame* %FramePtr, i32 0, i32 4
 ; CHECK:         [[XGEP:%.+]] = getelementptr inbounds %f.Frame, %f.Frame* %FramePtr, i32 0, i32 6
 ; CHECK:       init.ready:
 ; CHECK:         call void @llvm.dbg.declare(metadata i32* [[IGEP]], metadata ![[IVAR:[0-9]+]], metadata !DIExpression()), !dbg ![[IDBGLOC:[0-9]+]]
 ; CHECK:         call void @llvm.dbg.declare(metadata [10 x i32]* [[XGEP]], metadata ![[XVAR:[0-9]+]], metadata !DIExpression()), !dbg ![[IDBGLOC]]
 ; CHECK:       await.ready:
-; CHECK:         call void @llvm.dbg.value(metadata [10 x i32]* [[XGEP]], metadata ![[XVAR]], metadata !DIExpression()), !dbg ![[IDBGLOC]]
-; CHECK:         call void @llvm.dbg.value(metadata i32* [[IGEP]], metadata ![[IVAR]], metadata !DIExpression()), !dbg ![[IDBGLOC]]
+; CHECK:         call void @llvm.dbg.value(metadata [10 x i32]* [[XGEP]], metadata ![[XVAR]], metadata !DIExpression(DW_OP_deref)), !dbg ![[IDBGLOC]]
+; CHECK:         call void @llvm.dbg.value(metadata i32* [[IGEP]], metadata ![[IVAR]], metadata !DIExpression(DW_OP_deref)), !dbg ![[IDBGLOC]]
 ; CHECK:         call void @llvm.dbg.declare(metadata i32* %j, metadata ![[JVAR:[0-9]+]], metadata !DIExpression()), !dbg ![[JDBGLOC:[0-9]+]]
 ;
 ; CHECK-LABEL: define internal fastcc void @f.resume({{.*}}) {
 ; CHECK:       entry.resume:
 ; CHECK:         %j = alloca i32, align 4
 ; CHECK:         [[IGEP_RESUME:%.+]] = getelementptr inbounds %f.Frame, %f.Frame* %FramePtr, i32 0, i32 4
 ; CHECK:         [[XGEP_RESUME:%.+]] = getelementptr inbounds %f.Frame, %f.Frame* %FramePtr, i32 0, i32 6
 ; CHECK:       init.ready:
 ; CHECK:         call void @llvm.dbg.declare(metadata i32* [[IGEP_RESUME]], metadata ![[IVAR_RESUME:[0-9]+]], metadata !DIExpression()), !dbg ![[IDBGLOC_RESUME:[0-9]+]]
 ; CHECK:         call void @llvm.dbg.declare(metadata [10 x i32]* [[XGEP_RESUME]], metadata ![[XVAR_RESUME:[0-9]+]], metadata !DIExpression()), !dbg ![[IDBGLOC_RESUME]]
 ; CHECK:       await.ready:
-; CHECK:         call void @llvm.dbg.value(metadata [10 x i32]* [[XGEP_RESUME]], metadata ![[XVAR_RESUME]], metadata !DIExpression()), !dbg ![[IDBGLOC_RESUME]]
-; CHECK:         call void @llvm.dbg.value(metadata i32* [[IGEP_RESUME]], metadata ![[IVAR_RESUME]], metadata !DIExpression()), !dbg ![[IDBGLOC_RESUME]]
+; CHECK:         call void @llvm.dbg.value(metadata [10 x i32]* [[XGEP_RESUME]], metadata ![[XVAR_RESUME]], metadata !DIExpression(DW_OP_deref)), !dbg ![[IDBGLOC_RESUME]]
+; CHECK:         call void @llvm.dbg.value(metadata i32* [[IGEP_RESUME]], metadata ![[IVAR_RESUME]], metadata !DIExpression(DW_OP_deref)), !dbg ![[IDBGLOC_RESUME]]
 ; CHECK:         call void @llvm.dbg.declare(metadata i32* %j, metadata ![[JVAR_RESUME:[0-9]+]], metadata !DIExpression()), !dbg ![[JDBGLOC_RESUME:[0-9]+]]
 ;
 ; CHECK: ![[IVAR]] = !DILocalVariable(name: "i"
 ; CHECK: ![[SCOPE:[0-9]+]] = distinct !DILexicalBlock(scope: !8, file: !1, line: 23, column: 12)
 ; CHECK: ![[IDBGLOC]] = !DILocation(line: 24, column: 7, scope: ![[SCOPE]])
 ; CHECK: ![[XVAR]] = !DILocalVariable(name: "x"
 ; CHECK: ![[JVAR]] = !DILocalVariable(name: "j"
 ; CHECK: ![[JDBGLOC]] = !DILocation(line: 32, column: 7, scope: ![[SCOPE]])

 !14 = !DILocalVariable(name: "x", scope: !22, file: !1, line: 34, type: !15)
 !15 = !DICompositeType(tag: DW_TAG_array_type, baseType: !10, size: 320, elements: !16)
 !16 = !{!17}
 !17 = !DISubrange(count: 10)
 !18 = !DILocation(line: 42, column: 3, scope: !7)
 !19 = !DILocation(line: 42, column: 8, scope: !7)
 !20 = !DILocation(line: 43, column: 3, scope: !7)
 !21 = !DILocation(line: 43, column: 8, scope: !7)
-!22 = distinct !DILexicalBlock(scope: !8, file: !1, line: 23, column: 12)
+!22 = distinct !DILexicalBlock(scope: !8, file: !1, line: 23, column: 12)