Clean up the processing of dbg.value in various places

Summary:
First up is instcombine, where in the dbg.declare -> dbg.value conversion,
the llvm.dbg.value needs to be called on the actual loaded value, rather
than the address (since the whole point of this transformation is to be
able to get rid of the alloca). Further, now that that's cleaned up, we
can remove a hack in the backend, that would add an implicit OP_deref if
the argument to dbg.value was an alloca. This stems from before the
existence of DIExpression and is no longer necessary since the deref can
be expressed explicitly.

Now, in order to make sure that the tests pass with this change, we need to
correct the printing of DEBUG_VALUE comments to take into account the
expression, which wasn't taken into account before.

Unfortunately, for both these changes, there were a number of incorrect
test cases (mostly the wrong number of DW_OP_derefs, but also a couple
where the test itself was broken more badly). aprantl and I have gone
through and adjusted these test case in order to make them pass with
these fixes and in some cases to make sure they're actually testing
what they are meant to test.

Reviewers: aprantl

Subscribers: dsanders

Differential Revision: http://reviews.llvm.org/D14186

llvm-svn: 256077

llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp

@@ -775,6 +775,28 @@ static bool emitDebugValueComment(const MachineInstr *MI, AsmPrinter &AP) {
   bool Deref = MI->getOperand(0).isReg() && MI->getOperand(1).isImm();
   int64_t Offset = Deref ? MI->getOperand(1).getImm() : 0;
 
+  for (unsigned i = 0; i < Expr->getNumElements(); ++i) {
+    if (Deref) {
+      // We currently don't support extra Offsets or derefs after the first
+      // one. Bail out early instead of emitting an incorrect comment
+      OS << " [complex expression]";
+      AP.OutStreamer->emitRawComment(OS.str());
+      return true;
+    }
+    uint64_t Op = Expr->getElement(i);
+    if (Op == dwarf::DW_OP_deref) {
+      Deref = true;
+      continue;
+    }
+    uint64_t ExtraOffset = Expr->getElement(i++);
+    if (Op == dwarf::DW_OP_plus)
+      Offset += ExtraOffset;
+    else {
+      assert(Op == dwarf::DW_OP_minus);
+      Offset -= ExtraOffset;
+    }
+  }
+
   // Register or immediate value. Register 0 means undef.
   if (MI->getOperand(0).isFPImm()) {
     APFloat APF = APFloat(MI->getOperand(0).getFPImm()->getValueAPF());

llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp

@@ -950,14 +950,12 @@ void SelectionDAGBuilder::resolveDanglingDebugInfo(const Value *V,
     assert(Variable->isValidLocationForIntrinsic(dl) &&
            "Expected inlined-at fields to agree");
     uint64_t Offset = DI->getOffset();
-    // A dbg.value for an alloca is always indirect.
-    bool IsIndirect = isa<AllocaInst>(V) || Offset != 0;
     SDDbgValue *SDV;
     if (Val.getNode()) {
-      if (!EmitFuncArgumentDbgValue(V, Variable, Expr, dl, Offset, IsIndirect,
+      if (!EmitFuncArgumentDbgValue(V, Variable, Expr, dl, Offset, false,
                                     Val)) {
         SDV = DAG.getDbgValue(Variable, Expr, Val.getNode(), Val.getResNo(),
-                              IsIndirect, Offset, dl, DbgSDNodeOrder);
+                              false, Offset, dl, DbgSDNodeOrder);
         DAG.AddDbgValue(SDV, Val.getNode(), false);
       }
     } else
@@ -4515,12 +4513,10 @@ SelectionDAGBuilder::visitIntrinsicCall(const CallInst &I, unsigned Intrinsic) {
         // Check unused arguments map.
         N = UnusedArgNodeMap[V];
       if (N.getNode()) {
-        // A dbg.value for an alloca is always indirect.
-        bool IsIndirect = isa<AllocaInst>(V) || Offset != 0;
         if (!EmitFuncArgumentDbgValue(V, Variable, Expression, dl, Offset,
-                                      IsIndirect, N)) {
+                                      false, N)) {
           SDV = DAG.getDbgValue(Variable, Expression, N.getNode(), N.getResNo(),
-                                IsIndirect, Offset, dl, SDNodeOrder);
+                                false, Offset, dl, SDNodeOrder);
           DAG.AddDbgValue(SDV, N.getNode(), false);
         }
       } else if (!V->use_empty() ) {

llvm/lib/Transforms/Utils/Local.cpp

@@ -1071,8 +1071,13 @@ bool llvm::ConvertDebugDeclareToDebugValue(DbgDeclareInst *DDI,
   if (LdStHasDebugValue(DIVar, LI))
     return true;
 
-  Builder.insertDbgValueIntrinsic(LI->getOperand(0), 0, DIVar, DIExpr,
-                                  DDI->getDebugLoc(), LI);
+  // We are now tracking the loaded value instead of the address. In the
+  // future if multi-location support is added to the IR, it might be
+  // preferable to keep tracking both the loaded value and the original
+  // address in case the alloca can not be elided.
+  Instruction *DbgValue = Builder.insertDbgValueIntrinsic(
+      LI, 0, DIVar, DIExpr, DDI->getDebugLoc(), (Instruction *)nullptr);
+  DbgValue->insertAfter(LI);
   return true;
 }
 
@@ -1114,9 +1119,13 @@ bool llvm::LowerDbgDeclare(Function &F) {
           // This is a call by-value or some other instruction that
           // takes a pointer to the variable. Insert a *value*
           // intrinsic that describes the alloca.
+          SmallVector<uint64_t, 1> NewDIExpr;
+          auto *DIExpr = DDI->getExpression();
+          NewDIExpr.push_back(dwarf::DW_OP_deref);
+          NewDIExpr.append(DIExpr->elements_begin(), DIExpr->elements_end());
           DIB.insertDbgValueIntrinsic(AI, 0, DDI->getVariable(),
-                                      DDI->getExpression(), DDI->getDebugLoc(),
-                                      CI);
+                                      DIB.createExpression(NewDIExpr),
+                                      DDI->getDebugLoc(), CI);
         }
       DDI->eraseFromParent();
     }

llvm/test/CodeGen/ARM/debug-info-blocks.ll

@@ -1,5 +1,21 @@
-; RUN: llc -O0 < %s | FileCheck %s
-; CHECK: @DEBUG_VALUE: foobar_func_block_invoke_0:mydata <- [%SP+{{[0-9]+}}]
+; RUN: %llc_dwarf -filetype=obj -O0 < %s | llvm-dwarfdump  - | FileCheck %s
+
+; debug_info content
+; CHECK: DW_AT_name {{.*}} "foobar_func_block_invoke_0"
+; CHECK-NOT: DW_TAG_subprogram
+; CHECK: DW_TAG_variable
+; CHECK-NOT: DW_TAG
+; CHECK-NEXT: DW_AT_location [DW_FORM_sec_offset]	([[MYDATA_LOC:0x[0-9a-f]*]])
+; CHECK-NEXT: DW_AT_name {{.*}} "mydata"
+
+; debug_loc content
+; CHECK: .debug_loc contents:
+; CHECK: [[MYDATA_LOC]]: Beginning address offset: {{.*}}
+; CHECK-NOT: {{0x[0-9a-f]*}}: Beginning address offset
+; CHECK: Location description: {{.*}} 23 04 06 23 18
+; CHECK-NOT: {{0x[0-9a-f]*}}: Beginning address offset
+; CHECK: Location description: {{.*}} 23 04 06 23 18
+
 ; Radar 9331779
 target datalayout = "e-p:32:32:32-i1:8:32-i8:8:32-i16:16:32-i32:32:32-i64:32:32-f32:32:32-f64:32:32-v64:32:64-v128:32:128-a0:0:32-n32"
 target triple = "thumbv7-apple-ios"

llvm/test/DebugInfo/AArch64/coalescing.ll

@@ -60,6 +60,6 @@ attributes #3 = { nounwind optsize }
 !13 = !{i32 2, !"Debug Info Version", i32 3}
 !14 = !{!"clang version 3.6.0 (trunk 223149) (llvm/trunk 223115)"}
 !15 = !DILocation(line: 5, column: 3, scope: !4)
-!16 = !DIExpression()
+!16 = !DIExpression(DW_OP_deref)
 !17 = !DILocation(line: 4, column: 12, scope: !4)
 !18 = !DILocation(line: 8, column: 1, scope: !4)

llvm/test/DebugInfo/Mips/dsr-fixed-objects.ll

@@ -33,18 +33,18 @@ declare void @foo(i32*)
 define i32 @f0(i32 signext %a, i32 signext %b, i32 signext %c, i32 signext %d, i32 signext %e) !dbg !4 {
 entry:
   %x = alloca i32, align 4
-  tail call void @llvm.dbg.value(metadata i32 %a, i64 0, metadata !9, metadata !26), !dbg !27
-  tail call void @llvm.dbg.value(metadata i32 %b, i64 0, metadata !10, metadata !26), !dbg !28
-  tail call void @llvm.dbg.value(metadata i32 %c, i64 0, metadata !11, metadata !26), !dbg !29
-  tail call void @llvm.dbg.value(metadata i32 %d, i64 0, metadata !12, metadata !26), !dbg !30
-  tail call void @llvm.dbg.value(metadata i32 %e, i64 0, metadata !13, metadata !26), !dbg !31
+  tail call void @llvm.dbg.value(metadata i32 %a, i64 0, metadata !9,  metadata !DIExpression()), !dbg !27
+  tail call void @llvm.dbg.value(metadata i32 %b, i64 0, metadata !10, metadata !DIExpression()), !dbg !28
+  tail call void @llvm.dbg.value(metadata i32 %c, i64 0, metadata !11, metadata !DIExpression()), !dbg !29
+  tail call void @llvm.dbg.value(metadata i32 %d, i64 0, metadata !12, metadata !DIExpression()), !dbg !30
+  tail call void @llvm.dbg.value(metadata i32 %e, i64 0, metadata !13, metadata !DIExpression()), !dbg !31
   %0 = bitcast i32* %x to i8*, !dbg !32
   call void @llvm.lifetime.start(i64 4, i8* %0) #4, !dbg !32
   %add = add nsw i32 %b, %a, !dbg !33
   %add1 = add nsw i32 %add, %c, !dbg !34
   %add2 = add nsw i32 %add1, %d, !dbg !35
   %add3 = add nsw i32 %add2, %e, !dbg !36
-  tail call void @llvm.dbg.value(metadata i32 %add3, i64 0, metadata !14, metadata !26), !dbg !37
+  tail call void @llvm.dbg.value(metadata i32 %add3, i64 0, metadata !14, metadata !DIExpression()), !dbg !37
   store i32 %add3, i32* %x, align 4, !dbg !37, !tbaa !38
   tail call void @llvm.dbg.value(metadata i32* %x, i64 0, metadata !14, metadata !26), !dbg !37
   call void @foo(i32* nonnull %x) #4, !dbg !42
@@ -66,18 +66,18 @@ entry:
 define i32 @f1(i32 signext %a, i32 signext %b, i32 signext %c, i32 signext %d, i32 signext %e) !dbg !15 {
 entry:
   %x = alloca i32, align 16
-  tail call void @llvm.dbg.value(metadata i32 %a, i64 0, metadata !17, metadata !26), !dbg !46
-  tail call void @llvm.dbg.value(metadata i32 %b, i64 0, metadata !18, metadata !26), !dbg !47
-  tail call void @llvm.dbg.value(metadata i32 %c, i64 0, metadata !19, metadata !26), !dbg !48
-  tail call void @llvm.dbg.value(metadata i32 %d, i64 0, metadata !20, metadata !26), !dbg !49
-  tail call void @llvm.dbg.value(metadata i32 %e, i64 0, metadata !21, metadata !26), !dbg !50
+  tail call void @llvm.dbg.value(metadata i32 %a, i64 0, metadata !17, metadata !DIExpression()), !dbg !46
+  tail call void @llvm.dbg.value(metadata i32 %b, i64 0, metadata !18, metadata !DIExpression()), !dbg !47
+  tail call void @llvm.dbg.value(metadata i32 %c, i64 0, metadata !19, metadata !DIExpression()), !dbg !48
+  tail call void @llvm.dbg.value(metadata i32 %d, i64 0, metadata !20, metadata !DIExpression()), !dbg !49
+  tail call void @llvm.dbg.value(metadata i32 %e, i64 0, metadata !21, metadata !DIExpression()), !dbg !50
   %0 = bitcast i32* %x to i8*, !dbg !51
   call void @llvm.lifetime.start(i64 4, i8* %0) #4, !dbg !51
   %add = add nsw i32 %b, %a, !dbg !52
   %add1 = add nsw i32 %add, %c, !dbg !53
   %add2 = add nsw i32 %add1, %d, !dbg !54
   %add3 = add nsw i32 %add2, %e, !dbg !55
-  tail call void @llvm.dbg.value(metadata i32 %add3, i64 0, metadata !22, metadata !26), !dbg !56
+  tail call void @llvm.dbg.value(metadata i32 %add3, i64 0, metadata !22, metadata !DIExpression()), !dbg !56
   store i32 %add3, i32* %x, align 16, !dbg !56, !tbaa !38
   tail call void @llvm.dbg.value(metadata i32* %x, i64 0, metadata !22, metadata !26), !dbg !56
   call void @foo(i32* nonnull %x) #4, !dbg !57
@@ -119,7 +119,7 @@ declare void @llvm.dbg.value(metadata, i64, metadata, metadata)
 !23 = !{i32 2, !"Dwarf Version", i32 4}
 !24 = !{i32 2, !"Debug Info Version", i32 3}
 !25 = !{!"clang version 3.8.0 (trunk 251783) (llvm/trunk 251781)"}
-!26 = !DIExpression()
+!26 = !DIExpression(DW_OP_deref)
 !27 = !DILocation(line: 4, column: 12, scope: !4)
 !28 = !DILocation(line: 4, column: 19, scope: !4)
 !29 = !DILocation(line: 4, column: 26, scope: !4)

llvm/test/DebugInfo/X86/array.ll

@@ -37,13 +37,13 @@ define i32 @main(i32 %argc, i8** nocapture readnone %argv) #0 !dbg !12 {
   %array = alloca [4 x i32], align 16
   tail call void @llvm.dbg.value(metadata i32 %argc, i64 0, metadata !19, metadata !DIExpression()), !dbg !35
   tail call void @llvm.dbg.value(metadata i8** %argv, i64 0, metadata !20, metadata !DIExpression()), !dbg !35
-  tail call void @llvm.dbg.value(metadata [4 x i32]* %array, i64 0, metadata !21, metadata !DIExpression()), !dbg !36
+  tail call void @llvm.dbg.value(metadata [4 x i32]* %array, i64 0, metadata !21, metadata !DIExpression(DW_OP_deref)), !dbg !36
   %1 = bitcast [4 x i32]* %array to i8*, !dbg !36
   call void @llvm.memcpy.p0i8.p0i8.i64(i8* %1, i8* bitcast ([4 x i32]* @main.array to i8*), i64 16, i32 16, i1 false), !dbg !36
-  tail call void @llvm.dbg.value(metadata [4 x i32]* %array, i64 0, metadata !21, metadata !DIExpression()), !dbg !36
+  tail call void @llvm.dbg.value(metadata [4 x i32]* %array, i64 0, metadata !21, metadata !DIExpression(DW_OP_deref)), !dbg !36
   %2 = getelementptr inbounds [4 x i32], [4 x i32]* %array, i64 0, i64 0, !dbg !37
   call void @f(i32* %2), !dbg !37
-  tail call void @llvm.dbg.value(metadata [4 x i32]* %array, i64 0, metadata !21, metadata !DIExpression()), !dbg !36
+  tail call void @llvm.dbg.value(metadata [4 x i32]* %array, i64 0, metadata !21, metadata !DIExpression(DW_OP_deref)), !dbg !36
   %3 = load i32, i32* %2, align 16, !dbg !38, !tbaa !30
   ret i32 %3, !dbg !38
 }

llvm/test/DebugInfo/X86/dbg-value-const-byref.ll

@@ -56,7 +56,7 @@ entry:
   %call1 = call i32 (...) @f1() #3, !dbg !19
   call void @llvm.dbg.value(metadata i32 %call1, i64 0, metadata !10, metadata !DIExpression()), !dbg !19
   store i32 %call1, i32* %i, align 4, !dbg !19, !tbaa !20
-  call void @llvm.dbg.value(metadata i32* %i, i64 0, metadata !10, metadata !DIExpression()), !dbg !24
+  call void @llvm.dbg.value(metadata i32* %i, i64 0, metadata !10, metadata !DIExpression(DW_OP_deref)), !dbg !24
   call void @f2(i32* %i) #3, !dbg !24
   ret i32 0, !dbg !25
 }

llvm/test/DebugInfo/X86/debug-loc-asan.ll

@@ -7,15 +7,14 @@
 ; int bar(int y) {
 ;   return y + 2;
 ; }
-; with "clang++ -S -emit-llvm -fsanitize=address -O0 -g test.cc"
+; with "clang++ -S -emit-llvm -mllvm -asan-skip-promotable-allocas=0 -fsanitize=address -O0 -g test.cc"
 
-; First, argument variable "y" resides in %rdi:
-; CHECK: DEBUG_VALUE: bar:y <- %RDI
-
-; Then its address is stored in a location on a stack:
+; The address of the (potentially now malloc'ed) alloca ends up
+; in RDI, after which it is spilled to the stack. We record the
+; spill OFFSET on the stack for checking the debug info below.
+; CHECK: #DEBUG_VALUE: bar:y <- [%RDI+0]
 ; CHECK: movq %rdi, [[OFFSET:[0-9]+]](%rsp)
 ; CHECK-NEXT: [[START_LABEL:.Ltmp[0-9]+]]
-; CHECK-NEXT: DEBUG_VALUE: bar:y <- [%RSP+[[OFFSET]]]
 ; This location should be valid until the end of the function.
 
 ; CHECK: .Ldebug_loc{{[0-9]+}}:

llvm/test/DebugInfo/X86/op_deref.ll

@@ -20,11 +20,11 @@
 ; right now, so we check the asm output:
 ; RUN: llc -O0 -mtriple=x86_64-apple-darwin %s -o - -filetype=asm | FileCheck %s -check-prefix=ASM-CHECK
 ; vla should have a register-indirect address at one point.
-; ASM-CHECK: DEBUG_VALUE: vla <- %RCX
+; ASM-CHECK: DEBUG_VALUE: vla <- [%RCX+0]
 ; ASM-CHECK: DW_OP_breg2
 
 ; RUN: llvm-as %s -o - | llvm-dis - | FileCheck %s --check-prefix=PRETTY-PRINT
-; PRETTY-PRINT: DIExpression(DW_OP_deref, DW_OP_deref)
+; PRETTY-PRINT: DIExpression(DW_OP_deref)
 
 define void @testVLAwithSize(i32 %s) nounwind uwtable ssp !dbg !5 {
 entry:
@@ -108,4 +108,4 @@ declare void @llvm.stackrestore(i8*) nounwind
 !27 = !DILocation(line: 8, column: 1, scope: !13)
 !28 = !DIFile(filename: "bar.c", directory: "/Users/echristo/tmp")
 !29 = !{i32 1, !"Debug Info Version", i32 3}
-!30 = !DIExpression(DW_OP_deref, DW_OP_deref)
+!30 = !DIExpression(DW_OP_deref)

llvm/test/DebugInfo/X86/reference-argument.ll

@@ -22,14 +22,15 @@ target triple = "x86_64-apple-macosx10.9.0"
 
 declare void @_Z3barR4SVal(%class.SVal* %v)
 declare void @llvm.dbg.declare(metadata, metadata, metadata) #1
+declare void @llvm.dbg.value(metadata, i64, metadata, metadata) #1
 declare i32 @main()
 ; Function Attrs: nounwind ssp uwtable
 define linkonce_odr void @_ZN1A3fooE4SVal(%class.A* %this, %class.SVal* %v) nounwind ssp uwtable align 2 !dbg !35 {
 entry:
   %this.addr = alloca %class.A*, align 8
   store %class.A* %this, %class.A** %this.addr, align 8
   call void @llvm.dbg.declare(metadata %class.A** %this.addr, metadata !59, metadata !DIExpression()), !dbg !61
-  call void @llvm.dbg.declare(metadata %class.SVal* %v, metadata !62, metadata !DIExpression(DW_OP_deref)), !dbg !61
+  call void @llvm.dbg.value(metadata %class.SVal* %v, i64 0, metadata !62, metadata !DIExpression(DW_OP_deref)), !dbg !61
   %this1 = load %class.A*, %class.A** %this.addr
   call void @_Z3barR4SVal(%class.SVal* %v), !dbg !61
   ret void, !dbg !61

llvm/test/DebugInfo/X86/vla.ll

@@ -1,6 +1,6 @@
 ; RUN: llc -O0 -mtriple=x86_64-apple-darwin -filetype=asm %s -o - | FileCheck %s
 ; Ensure that we generate an indirect location for the variable length array a.
-; CHECK: ##DEBUG_VALUE: vla:a <- %RDX
+; CHECK: ##DEBUG_VALUE: vla:a <- [%RDX+0]
 ; CHECK: DW_OP_breg1
 ; rdar://problem/13658587
 ;

llvm/test/Transforms/Util/simplify-dbg-declare-load.ll

@@ -0,0 +1,52 @@
+; RUN: opt -instcombine -S < %s | FileCheck %s
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-pc-linux-gnu"
+
+%foo = type { i64, i32, i32 }
+
+; Function Attrs: nounwind readnone
+declare void @llvm.dbg.declare(metadata, metadata, metadata) #0
+declare void @llvm.dbg.value(metadata, i64, metadata, metadata) #0
+
+; Function Attrs: sspreq
+define void @julia_fastshortest_6256() #1 {
+top:
+  %cp = alloca %foo, align 8
+  call void @llvm.dbg.declare(metadata %foo* %cp, metadata !1, metadata !16), !dbg !17
+  br i1 undef, label %idxend, label %fail
+
+fail:                                             ; preds = %top
+  unreachable
+
+idxend:                                           ; preds = %top
+; CHECK-NOT call void @llvm.dbg.value(metadata %foo* %cp, i64 0, metadata !1, metadata !16), !dbg !17
+  %0 = load volatile %foo, %foo* %cp, align 8
+; CHECK: call void @llvm.dbg.value(metadata %foo %0, i64 0, metadata !1, metadata !16), !dbg !17
+  store volatile %foo %0, %foo* undef, align 8
+  ret void
+}
+
+attributes #0 = { nounwind readnone }
+attributes #1 = { sspreq }
+
+!llvm.module.flags = !{!0}
+!llvm.dbg.cu = !{}
+
+!0 = !{i32 1, !"Debug Info Version", i32 3}
+!1 = !DILocalVariable(name: "cp", scope: !2, file: !3, line: 106, type: !12)
+!2 = distinct !DISubprogram(name: "fastshortest", linkageName: "julia_fastshortest_6256", scope: null, file: !3, type: !4, isLocal: false, isDefinition: true, isOptimized: true, variables: !11)
+!3 = !DIFile(filename: "grisu/fastshortest.jl", directory: ".")
+!4 = !DISubroutineType(types: !5)
+!5 = !{!6, !7}
+!6 = !DIBasicType(name: "Float64", size: 64, align: 64, encoding: DW_ATE_unsigned)
+!7 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !8, size: 64, align: 64)
+!8 = !DICompositeType(tag: DW_TAG_structure_type, name: "jl_value_t", file: !9, line: 71, align: 64, elements: !10)
+!9 = !DIFile(filename: "julia.h", directory: "")
+!10 = !{!7}
+!11 = !{}
+!12 = !DICompositeType(tag: DW_TAG_structure_type, name: "Float", size: 128, align: 64, elements: !13, runtimeLang: DW_LANG_Julia)
+!13 = !{!14, !15, !15}
+!14 = !DIBasicType(name: "UInt64", size: 64, align: 64, encoding: DW_ATE_unsigned)
+!15 = !DIBasicType(name: "Int32", size: 32, align: 32, encoding: DW_ATE_unsigned)
+!16 = !DIExpression()
+!17 = !DILocation(line: 106, scope: !2)