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[Assignment Tracking][7/*] Add assignment tracking functionality to clang
The Assignment Tracking debug-info feature is outlined in this RFC: https://discourse.llvm.org/t/ rfc-assignment-tracking-a-better-way-of-specifying-variable-locations-in-ir This patch plumbs the AssignmentTrackingPass (AKA declare-to-assign), added in the previous patch in this set, into the optimisation pipeline from clang. clang/test/CodeGen/assignment-tracking/assignment-tracking.cpp is the main test for this patch. Note: while clang (with the help of the declare-to-assign pass) can now emit Assignment Tracking metadata, the llvm middle and back ends don't yet understand it. Reviewed By: jmorse Differential Revision: https://reviews.llvm.org/D132226
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‎clang/lib/CodeGen/BackendUtil.cpp

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#include "llvm/CodeGen/SchedulerRegistry.h"
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#include "llvm/CodeGen/TargetSubtargetInfo.h"
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#include "llvm/IR/DataLayout.h"
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#include "llvm/IR/DebugInfo.h"
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#include "llvm/IR/IRPrintingPasses.h"
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#include "llvm/IR/LegacyPassManager.h"
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#include "llvm/IR/Module.h"
@@ -830,6 +831,13 @@ void EmitAssemblyHelper::RunOptimizationPipeline(
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SI.registerCallbacks(PIC, &FAM);
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PassBuilder PB(TM.get(), PTO, PGOOpt, &PIC);
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if (CodeGenOpts.EnableAssignmentTracking) {
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PB.registerPipelineStartEPCallback(
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[&](ModulePassManager &MPM, OptimizationLevel Level) {
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MPM.addPass(AssignmentTrackingPass());
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});
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}
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// Enable verify-debuginfo-preserve-each for new PM.
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DebugifyEachInstrumentation Debugify;
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DebugInfoPerPass DebugInfoBeforePass;

‎clang/test/CodeGen/assignment-tracking/assignment-tracking.cpp

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// RUN: %clang_cc1 -triple x86_64-none-linux-gnu -debug-info-kind=standalone -O0 \
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// RUN: -emit-llvm -fexperimental-assignment-tracking %s -o - \
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// RUN: | FileCheck %s --implicit-check-not="call void @llvm.dbg"
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// Based on llvm/test/DebugInfo/Generic/track-assignments.ll - check that using
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// -Xclang -fexperimental-assignment-tracking results in emitting (or, as it is
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// set up currently, telling llvm to create) assignment tracking metadata.
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//
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// See the original test for more info.
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struct Inner { int A, B; };
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struct Outer { Inner A, B; };
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struct Large { int A[10]; };
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struct LCopyCtor { int A[4]; LCopyCtor(); LCopyCtor(LCopyCtor const &); };
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int Value, Index, Cond;
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Inner InnerA, InnerB;
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Large L;
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void zeroInit() { int Z[3] = {0, 0, 0}; }
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// CHECK-LABEL: define dso_local void @_Z8zeroInitv
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// CHECK: %Z = alloca [3 x i32], align 4, !DIAssignID ![[ID_0:[0-9]+]]
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// CHECK-NEXT: call void @llvm.dbg.assign(metadata i1 undef, metadata ![[VAR_0:[0-9]+]], metadata !DIExpression(), metadata ![[ID_0]], metadata [3 x i32]* %Z, metadata !DIExpression())
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// CHECK: @llvm.memset.p0i8.i64{{.*}}, !DIAssignID ![[ID_1:[0-9]+]]
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// CHECK-NEXT: call void @llvm.dbg.assign(metadata i8 0, metadata ![[VAR_0]], metadata !DIExpression(), metadata ![[ID_1]], metadata i8* %0, metadata !DIExpression())
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void memcpyInit() { int A[4] = {0, 1, 2, 3}; }
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// CHECK-LABEL: define dso_local void @_Z10memcpyInitv
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// CHECK: %A = alloca [4 x i32], align 16, !DIAssignID ![[ID_2:[0-9]+]]
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// CHECK-NEXT: call void @llvm.dbg.assign(metadata i1 undef, metadata ![[VAR_1:[0-9]+]], metadata !DIExpression(), metadata ![[ID_2]], metadata [4 x i32]* %A, metadata !DIExpression())
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// CHECK: @llvm.memcpy.p0i8.p0i8.i64{{.*}}, !DIAssignID ![[ID_3:[0-9]+]]
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// CHECK-NEXT: call void @llvm.dbg.assign(metadata i1 undef, metadata ![[VAR_1]], metadata !DIExpression(), metadata ![[ID_3]], metadata i8* %0, metadata !DIExpression())
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void setField() {
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Outer O;
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O.A.B = Value;
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}
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// CHECK-LABEL: define dso_local void @_Z8setFieldv
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// CHECK: %O = alloca %struct.Outer, align 4, !DIAssignID ![[ID_4:[0-9]+]]
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// CHECK-NEXT: call void @llvm.dbg.assign(metadata i1 undef, metadata ![[VAR_2:[0-9]+]], metadata !DIExpression(), metadata ![[ID_4]], metadata %struct.Outer* %O, metadata !DIExpression())
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// CHECK: store i32 %0, i32* %B, align 4,{{.*}}!DIAssignID ![[ID_5:[0-9]+]]
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// CHECK-NEXT: call void @llvm.dbg.assign(metadata i32 %0, metadata ![[VAR_2]], metadata !DIExpression(DW_OP_LLVM_fragment, 32, 32), metadata ![[ID_5]], metadata i32* %B, metadata !DIExpression())
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void unknownOffset() {
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int A[2];
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A[Index] = Value;
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}
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// CHECK-LABEL: define dso_local void @_Z13unknownOffsetv
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// CHECK: %A = alloca [2 x i32], align 4, !DIAssignID ![[ID_6:[0-9]+]]
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// CHECK-NEXT: call void @llvm.dbg.assign(metadata i1 undef, metadata ![[VAR_3:[0-9]+]], metadata !DIExpression(), metadata ![[ID_6]], metadata [2 x i32]* %A, metadata !DIExpression())
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Inner sharedAlloca() {
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if (Cond) {
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Inner A = InnerA;
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return A;
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} else {
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Inner B = InnerB;
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return B;
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}
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}
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// CHECK-LABEL: define dso_local i64 @_Z12sharedAllocav
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// CHECK: %retval = alloca %struct.Inner, align 4, !DIAssignID ![[ID_7:[0-9]+]]
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// CHECK-NEXT: call void @llvm.dbg.assign(metadata i1 undef, metadata ![[VAR_4:[0-9]+]], metadata !DIExpression(), metadata ![[ID_7]], metadata %struct.Inner* %retval, metadata !DIExpression())
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// CHECK-NEXT: call void @llvm.dbg.assign(metadata i1 undef, metadata ![[VAR_5:[0-9]+]], metadata !DIExpression(), metadata ![[ID_7]], metadata %struct.Inner* %retval, metadata !DIExpression())
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// CHECK: if.then:
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// CHECK: call void @llvm.memcpy{{.*}}, !DIAssignID ![[ID_8:[0-9]+]]
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// CHECK-NEXT: call void @llvm.dbg.assign(metadata i1 undef, metadata ![[VAR_4]], metadata !DIExpression(), metadata ![[ID_8]], metadata i8* %1, metadata !DIExpression())
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// CHECK-NEXT: call void @llvm.dbg.assign(metadata i1 undef, metadata ![[VAR_5]], metadata !DIExpression(), metadata ![[ID_8]], metadata i8* %1, metadata !DIExpression())
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// CHECK: if.else:
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// CHECK: call void @llvm.memcpy{{.*}}, !DIAssignID ![[ID_9:[0-9]+]]
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// CHECK-NEXT: call void @llvm.dbg.assign(metadata i1 undef, metadata ![[VAR_4]], metadata !DIExpression(), metadata ![[ID_9]], metadata i8* %2, metadata !DIExpression())
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// CHECK-NEXT: call void @llvm.dbg.assign(metadata i1 undef, metadata ![[VAR_5]], metadata !DIExpression(), metadata ![[ID_9]], metadata i8* %2, metadata !DIExpression())
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Large sret() {
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Large X = L;
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return X;
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}
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// CHECK-LABEL: define dso_local void @_Z4sretv
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// CHECK: llvm.dbg.declare
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void byval(Large X) {}
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// CHECK-LABEL: define dso_local void @_Z5byval5Large
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// CHECK: llvm.dbg.declare
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LCopyCtor indirectReturn() {
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LCopyCtor R;
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return R;
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}
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// CHECK-LABEL: define dso_local void @_Z14indirectReturnv
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// CHECK: call void @llvm.dbg.declare
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// CHECK-DAG: ![[VAR_0]] = !DILocalVariable(name: "Z",
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// CHECK-DAG: ![[VAR_1]] = !DILocalVariable(name: "A",
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// CHECK-DAG: ![[VAR_2]] = !DILocalVariable(name: "O",
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// CHECK-DAG: ![[VAR_3]] = !DILocalVariable(name: "A",
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// CHECK-DAG: ![[VAR_4]] = !DILocalVariable(name: "B",
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// CHECK-DAG: ![[VAR_5]] = !DILocalVariable(name: "A",

‎clang/test/CodeGen/assignment-tracking/flag.cpp

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// RUN: %clang_cc1 -triple x86_64-none-linux-gnu -debug-info-kind=standalone -O0 \
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// RUN: -emit-llvm -fexperimental-assignment-tracking %s -o - \
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// RUN: | FileCheck %s --check-prefixes=FLAG
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// RUN: %clang_cc1 -triple x86_64-none-linux-gnu -debug-info-kind=standalone -O0 \
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// RUN: -emit-llvm %s -o - \
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// RUN: | FileCheck %s --check-prefixes=NO-FLAG
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// Check some assignment-tracking stuff appears in the output when the flag
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// -fexperimental-assignment-tracking is used, and that it doesn't when
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// the flag is not used (default behaviour: no assignment tracking).
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// FLAG: DIAssignID
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// FLAG: dbg.assign
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// NO-FLAG-NOT: DIAssignID
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// NO-FLAG-NOT: dbg.assign
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void fun(int a) {}

‎clang/test/CodeGen/assignment-tracking/memcpy-fragment.cpp

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// RUN: %clang_cc1 -triple x86_64-none-linux-gnu -debug-info-kind=standalone -O0 \
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// RUN: -emit-llvm -fexperimental-assignment-tracking %s -o - \
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// RUN: | FileCheck %s
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// Check that the (debug) codegen looks right with assignment tracking
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// enabled. Each fragment that is written to should have a dbg.assign that has
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// the DIAssignID of the write as an argument. The fragment offset and size
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// should match the offset into the base storage and size of the store. Each of
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// the scenarios below results in slightly different arguments generated for
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// the memcpy.
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// Test write a complete struct field only.
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void fragmentWhole()
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{
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struct Record {
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int num;
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char ch;
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};
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Record dest;
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char src = '\0';
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__builtin_memcpy(&dest.ch, &src, sizeof(char));
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}
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// CHECK: call void @llvm.memcpy.p0i8.p0i8.i64(i8* align 4 %ch, i8* align 1 %src, i64 1, i1 false), !dbg !{{[0-9]+}}, !DIAssignID ![[memberID:[0-9]+]]
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// CHECK-NEXT: call void @llvm.dbg.assign(metadata{{.*}}undef, metadata !{{[0-9]+}}, metadata !DIExpression(DW_OP_LLVM_fragment, 32, 8), metadata ![[memberID]], metadata i8* %ch, metadata !DIExpression())
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// Write starting at a field and overlapping part of another.
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void fragmentWholeToPartial()
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{
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struct Record {
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int num1;
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int num2;
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};
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Record dest;
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char src[5]="\0\0\0\0";
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__builtin_memcpy(&dest.num1, &src, 5);
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}
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// CHECK: call void @llvm.memcpy.p0i8.p0i8.i64(i8* align 4 %1, i8* align 1 %2, i64 5, i1 false), !dbg !{{[0-9]+}}, !DIAssignID ![[exceed:[0-9]+]]
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// CHECK-NEXT: call void @llvm.dbg.assign(metadata{{.*}}undef, metadata !{{[0-9]+}}, metadata !DIExpression(DW_OP_LLVM_fragment, 0, 40), metadata ![[exceed]], metadata i8* %1, metadata !DIExpression())
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// Write starting between fields.
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void fragmentPartialToWhole()
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{
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struct record {
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int num1;
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int num2;
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int num3;
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};
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record dest;
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char src[5]="\0\0\0\0";
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__builtin_memcpy((char*)&(dest.num2) + 3, &src, 5);
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}
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// CHECK: call void @llvm.memcpy.p0i8.p0i8.i64(i8* align 1 %add.ptr, i8* align 1 %2, i64 5, i1 false), !dbg !{{[0-9]+}}, !DIAssignID ![[addendID:[0-9]+]]
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// CHECK-NEXT: call void @llvm.dbg.assign(metadata{{.*}}undef, metadata !{{.*}}, metadata !DIExpression(DW_OP_LLVM_fragment, 56, 40), metadata ![[addendID]], metadata i8* %add.ptr, metadata !DIExpression())

‎clang/test/CodeGen/assignment-tracking/nested-scope.cpp

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// RUN: %clang_cc1 -triple x86_64-none-linux-gnu -debug-info-kind=standalone -O0 \
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// RUN: -emit-llvm -fexperimental-assignment-tracking %s -o - \
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// RUN: | FileCheck %s
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// Check that dbg.assign intrinsics get a !dbg with with the same scope as
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// their variable.
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// CHECK: call void @llvm.dbg.assign({{.+}}, metadata [[local:![0-9]+]], {{.+}}, {{.+}}, {{.+}}), !dbg [[dbg:![0-9]+]]
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// CHECK-DAG: [[local]] = !DILocalVariable(name: "local", scope: [[scope:![0-9]+]],
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// CHECK-DAG: [[dbg]] = !DILocation({{.+}}, scope: [[scope]])
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// CHECK-DAG: [[scope]] = distinct !DILexicalBlock
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void ext(int*);
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void fun() {
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{
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int local;
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}
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}
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‎clang/test/Driver/assignment-tracking-opts.c

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// RUN: %clang -### -S %s -g -target x86_64-linux-gnu 2>&1 | FileCheck --check-prefix=CHECK-NO-AT %s
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// RUN: %clang -### -S %s -g -target x86_64-linux-gnu 2>&1 \
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// RUN: -Xclang -fexperimental-assignment-tracking \
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// RUN: | FileCheck --check-prefix=CHECK-AT %s
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// CHECK-NO-AT-NOT: "-mllvm" "-experimental-assignment-tracking"
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// CHECK-NO-AT-NOT: "-fexperimental-assignment-tracking"
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// CHECK-AT: "-mllvm" "-experimental-assignment-tracking"
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// CHECK-AT: "-fexperimental-assignment-tracking"

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