[WebAssembly] Use DebugValueManager only when subprogram exists (#77978)

We previously scanned the whole BB for `DBG_VALUE` instruction even when
the program doesn't have debug info, i.e., the function doesn't have a
subprogram associated with it, which can make compilation unnecessarily
slow. This disables `DebugValueManager` when a `DISubprogram` doesn't
exist for a function.

This only reduces unnecessary work in non-debug mode and does not change
output, so it's hard to add a test to test this behavior.

Test changes were necessary because their `DISubprogram`s were not
correctly linked with the functions, so with this PR the compiler
incorrectly assumed the functions didn't have a subprogram and the tests
started to fail.

Fixes emscripten-core/emscripten#21048.

Author: aheejin

llvm/lib/Target/WebAssembly/WebAssemblyDebugValueManager.cpp

@@ -17,11 +17,15 @@
 #include "WebAssemblyMachineFunctionInfo.h"
 #include "llvm/CodeGen/MachineInstr.h"
 #include "llvm/IR/DebugInfoMetadata.h"
+#include "llvm/IR/Function.h"
 
 using namespace llvm;
 
 WebAssemblyDebugValueManager::WebAssemblyDebugValueManager(MachineInstr *Def)
     : Def(Def) {
+  if (!Def->getMF()->getFunction().getSubprogram())
+    return;
+
   // This code differs from MachineInstr::collectDebugValues in that it scans
   // the whole BB, not just contiguous DBG_VALUEs, until another definition to
   // the same register is encountered.

llvm/test/CodeGen/WebAssembly/cfg-stackify-dbg-skip.ll

@@ -15,7 +15,7 @@
 
 target triple = "wasm32-unknown-unknown"
 
-define void @foo(i64 %arg) {
+define void @foo(i64 %arg) !dbg !37 {
 start:
   %val = trunc i64 %arg to i32
   %cmp = icmp eq i32 %val, 0
@@ -39,7 +39,7 @@ declare void @llvm.dbg.value(metadata, metadata, metadata)
 !22 = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "&str", file: !6, size: 64, align: 32, elements: !{}, identifier: "111094d970b097647de579f9c509ef08")
 !33 = !{i32 2, !"Debug Info Version", i32 3}
 !35 = distinct !DILexicalBlock(scope: !37, file: !6, line: 357, column: 8)
-!37 = distinct !DISubprogram(name: "foobar", linkageName: "_fooba", scope: !38, file: !6, line: 353, type: !39, isLocal: true, isDefinition: true, scopeLine: 353, flags: DIFlagPrototyped, isOptimized: true, unit: !0, templateParams: !2, retainedNodes: !42)
+!37 = distinct !DISubprogram(name: "foo", scope: !6, file: !6, line: 353, type: !39, isLocal: true, isDefinition: true, scopeLine: 353, flags: DIFlagPrototyped, isOptimized: true, unit: !0, templateParams: !2, retainedNodes: !42)
 !38 = !DINamespace(name: "ptr", scope: null)
 !39 = !DISubroutineType(types: !2)
 !42 = !{!46}

llvm/test/DebugInfo/WebAssembly/dbg-value-move-clone.mir

@@ -20,7 +20,7 @@
   declare void @foo(i32)
   declare i32 @bar()
 
-  define void @test(i64 %arg) {
+  define void @test(i64 %arg) !dbg !6 {
     unreachable
   }
 
@@ -32,7 +32,7 @@
   !3 = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "&str", file: !2, size: 64, align: 32, elements: !{}, identifier: "111094d970b097647de579f9c509ef08")
   !4 = !{i32 2, !"Debug Info Version", i32 3}
   !5 = distinct !DILexicalBlock(scope: !6, file: !2, line: 357, column: 8)
-  !6 = distinct !DISubprogram(name: "testfoo", linkageName: "_testba", scope: !7, file: !2, line: 353, type: !8, isLocal: true, isDefinition: true, scopeLine: 353, flags: DIFlagPrototyped, isOptimized: true, unit: !0, templateParams: !1, retainedNodes: !9)
+  !6 = distinct !DISubprogram(name: "test", scope: !7, file: !2, line: 353, type: !8, isLocal: true, isDefinition: true, scopeLine: 353, flags: DIFlagPrototyped, isOptimized: true, unit: !0, templateParams: !1, retainedNodes: !9)
   !7 = !DINamespace(name: "ptr", scope: null)
   !8 = !DISubroutineType(types: !1)
   !9 = !{!10}

llvm/test/DebugInfo/WebAssembly/dbg-value-reg-stackify.mir

@@ -8,44 +8,44 @@
   declare void @use(i32)
   declare void @use_2(i32, i32)
 
-  define void @sink_simple() {
+  define void @sink_simple() !dbg !6 {
     call void @llvm.dbg.value(metadata i32 0, metadata !5, metadata !DIExpression()), !dbg !10
     call void @llvm.dbg.value(metadata i32 0, metadata !11, metadata !DIExpression()), !dbg !10
     call void @llvm.dbg.value(metadata i32 0, metadata !12, metadata !DIExpression()), !dbg !10
     call void @llvm.dbg.value(metadata i32 0, metadata !13, metadata !DIExpression()), !dbg !10
     ret void
   }
-  define void @sink_non_consecutive() {
+  define void @sink_non_consecutive() !dbg !14 {
     unreachable
   }
-  define void @dont_sink_above_def() {
+  define void @dont_sink_above_def() !dbg !15 {
     unreachable
   }
-  define void @sink_to_same_place() {
+  define void @sink_to_same_place() !dbg !16 {
     unreachable
   }
-  define void @cannot_sink_across_same_variable() {
+  define void @cannot_sink_across_same_variable() !dbg !17 {
     unreachable
   }
-  define void @cannot_sink_across_same_variable2() {
+  define void @cannot_sink_across_same_variable2() !dbg !18 {
     unreachable
   }
-  define void @can_sink_across_same_variable_with_same_const() {
+  define void @can_sink_across_same_variable_with_same_const() !dbg !19 {
     unreachable
   }
-  define void @sink_multiple_defs() {
+  define void @sink_multiple_defs() !dbg !20 {
     unreachable
   }
-  define void @clone_same_bb() {
+  define void @clone_same_bb() !dbg !21 {
     unreachable
   }
-  define void @clone_different_bb() {
+  define void @clone_different_bb() !dbg !22 {
     unreachable
   }
-  define void @tee_with_two_use_insts() {
+  define void @tee_with_two_use_insts() !dbg !23 {
     unreachable
   }
-  define void @tee_with_one_inst_with_two_uses() {
+  define void @tee_with_one_inst_with_two_uses() !dbg !24 {
     unreachable
   }
   declare void @llvm.dbg.value(metadata, metadata, metadata)
@@ -81,6 +81,17 @@
   ; CHECK: ![[VAR_C:[0-9]+]] = !DILocalVariable(name: "var_c"
   !13 = !DILocalVariable(name: "var_d", scope: !6, file: !1, line: 2, type: !9)
   ; CHECK: ![[VAR_D:[0-9]+]] = !DILocalVariable(name: "var_d"
+  !14 = distinct !DISubprogram(name: "sink_non_consecutive", scope: !1, file: !1, line: 1, type: !7, scopeLine: 1, unit: !0)
+  !15 = distinct !DISubprogram(name: "dont_sink_above_def", scope: !1, file: !1, line: 1, type: !7, scopeLine: 1, unit: !0)
+  !16 = distinct !DISubprogram(name: "sink_to_same_place", scope: !1, file: !1, line: 1, type: !7, scopeLine: 1, unit: !0)
+  !17 = distinct !DISubprogram(name: "cannot_sink_across_same_variable", scope: !1, file: !1, line: 1, type: !7, scopeLine: 1, unit: !0)
+  !18 = distinct !DISubprogram(name: "cannot_sink_across_same_variable2", scope: !1, file: !1, line: 1, type: !7, scopeLine: 1, unit: !0)
+  !19 = distinct !DISubprogram(name: "can_sink_across_same_variable_with_same_const", scope: !1, file: !1, line: 1, type: !7, scopeLine: 1, unit: !0)
+  !20 = distinct !DISubprogram(name: "sink_multiple_defs", scope: !1, file: !1, line: 1, type: !7, scopeLine: 1, unit: !0)
+  !21 = distinct !DISubprogram(name: "clone_same_bb", scope: !1, file: !1, line: 1, type: !7, scopeLine: 1, unit: !0)
+  !22 = distinct !DISubprogram(name: "clone_different_bb", scope: !1, file: !1, line: 1, type: !7, scopeLine: 1, unit: !0)
+  !23 = distinct !DISubprogram(name: "tee_with_two_use_insts", scope: !1, file: !1, line: 1, type: !7, scopeLine: 1, unit: !0)
+  !24 = distinct !DISubprogram(name: "tee_with_one_inst_with_two_uses", scope: !1, file: !1, line: 1, type: !7, scopeLine: 1, unit: !0)
 ...
 
 ---