Add DebugLoc information to WebAssembly block and loop.

[yurydelendik]

Add test description.

[dschuff]

Otherwise LGTM

test/CodeGen/WebAssembly/dbg-loop-loc.ll

2

This test probably belongs in test/DebugInfo/WebAssembly

5

Can you also include a comment with the source of dbg-loop-loc.c to make it easy to regenerate this file?

[yurydelendik]

Move test to the test/DebugInfo/WebAssembly and add C code source.

[dschuff]

Do you want me to commit this?

include/llvm/CodeGen/MachineBasicBlock.h

#endif
 
   /// Find the next valid DebugLoc starting at MBBI, skipping any DBG_VALUE
   /// instructions.  Return UnknownLoc if there is none.
   DebugLoc findDebugLoc(instr_iterator MBBI);
   DebugLoc findDebugLoc(iterator MBBI) {
     return findDebugLoc(MBBI.getInstrIterator());
   }
 
+  /// Find the previous valid DebugLoc preceding MBBI, skipping and DBG_VALUE
+  /// instructions.  Return UnknownLoc if there is none.
+  DebugLoc findPrevDebugLoc(instr_iterator MBBI);
+  DebugLoc findPrevDebugLoc(iterator MBBI) {
+    return findPrevDebugLoc(MBBI.getInstrIterator());
+  }
+
   /// Find and return the merged DebugLoc of the branch instructions of the
   /// block. Return UnknownLoc if there is none.
   DebugLoc findBranchDebugLoc();
 
   /// Possible outcome of a register liveness query to computeRegisterLiveness()
   enum LivenessQueryResult {
     LQR_Live,   ///< Register is known to be (at least partially) live.
     LQR_Dead,   ///< Register is known to be fully dead.

lib/CodeGen/MachineBasicBlock.cpp

 MachineBasicBlock::findDebugLoc(instr_iterator MBBI) {
   // Skip debug declarations, we don't want a DebugLoc from them.
   MBBI = skipDebugInstructionsForward(MBBI, instr_end());
   if (MBBI != instr_end())
     return MBBI->getDebugLoc();
   return {};
 }
 
+/// Find the previous valid DebugLoc preceding MBBI, skipping and DBG_VALUE
+/// instructions.  Return UnknownLoc if there is none.
+DebugLoc
+MachineBasicBlock::findPrevDebugLoc(instr_iterator MBBI) {
+  if (MBBI == instr_begin())
+    return {};
+  // Skip debug declarations, we don't want a DebugLoc from them.                 
+  MBBI = skipDebugInstructionsBackward(std::prev(MBBI), instr_begin());
+  if (!MBBI->isDebugValue())
+    return MBBI->getDebugLoc();
+  return {};
+} 
+
 /// Find and return the merged DebugLoc of the branch instructions of the block.
 /// Return UnknownLoc if there is none.
 DebugLoc
 MachineBasicBlock::findBranchDebugLoc() {
   DebugLoc DL;
   auto TI = getFirstTerminator();
   while (TI != end() && !TI->isBranch())
     ++TI;

lib/Target/WebAssembly/WebAssemblyCFGStackify.cpp

while (InsertPos != Header->begin() &&
            WebAssembly::isChild(*std::prev(InsertPos), MFI) &&
            std::prev(InsertPos)->getOpcode() != WebAssembly::LOOP &&
            std::prev(InsertPos)->getOpcode() != WebAssembly::END_BLOCK &&
            std::prev(InsertPos)->getOpcode() != WebAssembly::END_LOOP)
       --InsertPos;
   }
 
   // Add the BLOCK.
-  MachineInstr *Begin = BuildMI(*Header, InsertPos, DebugLoc(),
+  MachineInstr *Begin = BuildMI(*Header, InsertPos, MBB.findDebugLoc(InsertPos),
                                 TII.get(WebAssembly::BLOCK))
       .addImm(int64_t(WebAssembly::ExprType::Void));
 
   // Mark the end of the block.
   InsertPos = MBB.begin();
   while (InsertPos != MBB.end() &&
          InsertPos->getOpcode() == WebAssembly::END_LOOP &&
          LoopTops[&*InsertPos]->getParent()->getNumber() >= Header->getNumber())
     ++InsertPos;
-  MachineInstr *End = BuildMI(MBB, InsertPos, DebugLoc(),
+  MachineInstr *End = BuildMI(MBB, InsertPos, MBB.findPrevDebugLoc(InsertPos),
                               TII.get(WebAssembly::END_BLOCK));
   BlockTops[End] = Begin;
 
   // Track the farthest-spanning scope that ends at this point.
   int Number = MBB.getNumber();
   if (!ScopeTops[Number] ||
       ScopeTops[Number]->getNumber() > Header->getNumber())
     ScopeTops[Number] = Header;
static void PlaceLoopMarker(
   MachineBasicBlock *AfterLoop = &*Iter;
 
   // Mark the beginning of the loop (after the end of any existing loop that
   // ends here).
   auto InsertPos = MBB.begin();
   while (InsertPos != MBB.end() &&
          InsertPos->getOpcode() == WebAssembly::END_LOOP)
     ++InsertPos;
-  MachineInstr *Begin = BuildMI(MBB, InsertPos, DebugLoc(),
+  MachineInstr *Begin = BuildMI(MBB, InsertPos, MBB.findDebugLoc(InsertPos),
                                 TII.get(WebAssembly::LOOP))
       .addImm(int64_t(WebAssembly::ExprType::Void));
 
-  // Mark the end of the loop.
-  MachineInstr *End = BuildMI(*AfterLoop, AfterLoop->begin(), DebugLoc(),
+  // Mark the end of the loop (using arbitrary debug location that branched
+  // to the loop end as its location).
+  DebugLoc EndDL = (*AfterLoop->pred_rbegin())->findBranchDebugLoc();
+  MachineInstr *End = BuildMI(*AfterLoop, AfterLoop->begin(), EndDL,
                               TII.get(WebAssembly::END_LOOP));
   LoopTops[End] = Begin;
 
   assert((!ScopeTops[AfterLoop->getNumber()] ||
           ScopeTops[AfterLoop->getNumber()]->getNumber() < MBB.getNumber()) &&
          "With block sorting the outermost loop for a block should be first.");
   if (!ScopeTops[AfterLoop->getNumber()])
     ScopeTops[AfterLoop->getNumber()] = &MBB;
static void FixEndsAtEndOfFunction(
   }
 }
 
 // WebAssembly functions end with an end instruction, as if the function body
 // were a block.
 static void AppendEndToFunction(
     MachineFunction &MF,
     const WebAssemblyInstrInfo &TII) {
-  BuildMI(MF.back(), MF.back().end(), DebugLoc(),
+  BuildMI(MF.back(), MF.back().end(),
+          MF.back().findPrevDebugLoc(MF.back().end()),
           TII.get(WebAssembly::END_FUNCTION));
 }
 
 /// Insert LOOP and BLOCK markers at appropriate places.
 static void PlaceMarkers(MachineFunction &MF, const MachineLoopInfo &MLI,
                          const WebAssemblyInstrInfo &TII,
                          MachineDominatorTree &MDT,
                          WebAssemblyFunctionInfo &MFI) {

test/CodeGen/WebAssembly/dbg-loop-loc.ll

+; RUN: llc < %s -O0 -verify-machineinstrs | FileCheck %s
+
+; ModuleID = 'dbg-loop-loc.bc'
+source_filename = "dbg-loop-loc.c"
+target datalayout = "e-m:e-p:32:32-i64:64-n32:64-S128"
+target triple = "wasm32-unknown-unknown-wasm"
+
+; CHECK: .file 1
+; CHECK: .loc 1 1 0
+; CHECK: .loc 1 3 15
+; CHECK-NEXT: block
+; CHECK-NEXT: loop
+; CHECK: br 0
+; CHECK-NOT: .loc 1 0
+; CHECK: end_loop
+; CHECK: end_block
+; CHECK-NOT: .loc 1 0
+; CHECK: end_function
+
+; Function Attrs: noinline nounwind optnone
+define hidden i32 @fib(i32 %n) #0 !dbg !7 {
+entry:
+  %n.addr = alloca i32, align 4
+  %i = alloca i32, align 4
+  %t = alloca i32, align 4
+  %a = alloca i32, align 4
+  %b = alloca i32, align 4
+  store i32 %n, i32* %n.addr, align 4
+  call void @llvm.dbg.declare(metadata i32* %n.addr, metadata !11, metadata !DIExpression()), !dbg !12
+  call void @llvm.dbg.declare(metadata i32* %i, metadata !13, metadata !DIExpression()), !dbg !14
+  call void @llvm.dbg.declare(metadata i32* %t, metadata !15, metadata !DIExpression()), !dbg !16
+  call void @llvm.dbg.declare(metadata i32* %a, metadata !17, metadata !DIExpression()), !dbg !18
+  store i32 0, i32* %a, align 4, !dbg !18
+  call void @llvm.dbg.declare(metadata i32* %b, metadata !19, metadata !DIExpression()), !dbg !20
+  store i32 1, i32* %b, align 4, !dbg !20
+  store i32 0, i32* %i, align 4, !dbg !21
+  br label %for.cond, !dbg !23
+
+for.cond:                                         ; preds = %for.inc, %entry
+  %0 = load i32, i32* %i, align 4, !dbg !24
+  %1 = load i32, i32* %n.addr, align 4, !dbg !26
+  %cmp = icmp slt i32 %0, %1, !dbg !27
+  br i1 %cmp, label %for.body, label %for.end, !dbg !28
+
+for.body:                                         ; preds = %for.cond
+  %2 = load i32, i32* %a, align 4, !dbg !29
+  %3 = load i32, i32* %b, align 4, !dbg !31
+  %add = add nsw i32 %2, %3, !dbg !32
+  store i32 %add, i32* %t, align 4, !dbg !33
+  %4 = load i32, i32* %b, align 4, !dbg !34
+  store i32 %4, i32* %a, align 4, !dbg !35
+  %5 = load i32, i32* %t, align 4, !dbg !36
+  store i32 %5, i32* %b, align 4, !dbg !37
+  br label %for.inc, !dbg !38
+
+for.inc:                                          ; preds = %for.body
+  %6 = load i32, i32* %i, align 4, !dbg !39
+  %inc = add nsw i32 %6, 1, !dbg !39
+  store i32 %inc, i32* %i, align 4, !dbg !39
+  br label %for.cond, !dbg !40, !llvm.loop !41
+
+for.end:                                          ; preds = %for.cond
+  %7 = load i32, i32* %b, align 4, !dbg !43
+  ret i32 %7, !dbg !44
+}
+
+; Function Attrs: nounwind readnone speculatable
+declare void @llvm.dbg.declare(metadata, metadata, metadata) #1
+
+attributes #0 = { noinline nounwind optnone "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="false" "no-infs-fp-math"="false" "no-jump-tables"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="generic" "unsafe-fp-math"="false" "use-soft-float"="false" }
+attributes #1 = { nounwind readnone speculatable }
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!3, !4, !5}
+!llvm.ident = !{!6}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 7.0.0 (trunk 326837)", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !2)
+!1 = !DIFile(filename: "dbg-loop-loc.c", directory: "/Users/yury/llvmwasm")
+!2 = !{}
+!3 = !{i32 2, !"Dwarf Version", i32 4}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = !{i32 1, !"wchar_size", i32 4}
+!6 = !{!"clang version 7.0.0 (trunk 326837)"}
+!7 = distinct !DISubprogram(name: "fib", scope: !1, file: !1, line: 1, type: !8, isLocal: false, isDefinition: true, scopeLine: 1, flags: DIFlagPrototyped, isOptimized: false, unit: !0, variables: !2)
+!8 = !DISubroutineType(types: !9)
+!9 = !{!10, !10}
+!10 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!11 = !DILocalVariable(name: "n", arg: 1, scope: !7, file: !1, line: 1, type: !10)
+!12 = !DILocation(line: 1, column: 13, scope: !7)
+!13 = !DILocalVariable(name: "i", scope: !7, file: !1, line: 2, type: !10)
+!14 = !DILocation(line: 2, column: 7, scope: !7)
+!15 = !DILocalVariable(name: "t", scope: !7, file: !1, line: 2, type: !10)
+!16 = !DILocation(line: 2, column: 10, scope: !7)
+!17 = !DILocalVariable(name: "a", scope: !7, file: !1, line: 2, type: !10)
+!18 = !DILocation(line: 2, column: 13, scope: !7)
+!19 = !DILocalVariable(name: "b", scope: !7, file: !1, line: 2, type: !10)
+!20 = !DILocation(line: 2, column: 20, scope: !7)
+!21 = !DILocation(line: 3, column: 10, scope: !22)
+!22 = distinct !DILexicalBlock(scope: !7, file: !1, line: 3, column: 3)
+!23 = !DILocation(line: 3, column: 8, scope: !22)
+!24 = !DILocation(line: 3, column: 15, scope: !25)
+!25 = distinct !DILexicalBlock(scope: !22, file: !1, line: 3, column: 3)
+!26 = !DILocation(line: 3, column: 19, scope: !25)
+!27 = !DILocation(line: 3, column: 17, scope: !25)
+!28 = !DILocation(line: 3, column: 3, scope: !22)
+!29 = !DILocation(line: 4, column: 9, scope: !30)
+!30 = distinct !DILexicalBlock(scope: !25, file: !1, line: 3, column: 27)
+!31 = !DILocation(line: 4, column: 13, scope: !30)
+!32 = !DILocation(line: 4, column: 11, scope: !30)
+!33 = !DILocation(line: 4, column: 7, scope: !30)
+!34 = !DILocation(line: 4, column: 20, scope: !30)
+!35 = !DILocation(line: 4, column: 18, scope: !30)
+!36 = !DILocation(line: 4, column: 27, scope: !30)
+!37 = !DILocation(line: 4, column: 25, scope: !30)
+!38 = !DILocation(line: 5, column: 3, scope: !30)
+!39 = !DILocation(line: 3, column: 23, scope: !25)
+!40 = !DILocation(line: 3, column: 3, scope: !25)
+!41 = distinct !{!41, !28, !42}
+!42 = !DILocation(line: 5, column: 3, scope: !22)
+!43 = !DILocation(line: 6, column: 10, scope: !7)
+!44 = !DILocation(line: 6, column: 3, scope: !7)