[PATCH] D101736: [WebAssembly] Allow DBG_VALUE after terminator in MachineVerifier

[Heejin Ahn via Phabricator via llvm-commits]

aheejin updated this revision to Diff 342461.
aheejin added a comment.

ll file indentation fix


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D101736/new/

https://reviews.llvm.org/D101736

Files:
  llvm/lib/CodeGen/MachineVerifier.cpp
  llvm/test/CodeGen/WebAssembly/stackified-debug.ll


Index: llvm/test/CodeGen/WebAssembly/stackified-debug.ll
===================================================================
--- llvm/test/CodeGen/WebAssembly/stackified-debug.ll
+++ llvm/test/CodeGen/WebAssembly/stackified-debug.ll
@@ -1,4 +1,4 @@
-; RUN: llc < %s | FileCheck %s
+; RUN: llc -verify-machineinstrs < %s | FileCheck %s
 
 ; Input C code:
 
@@ -42,8 +42,6 @@
 ; CHECK: 	.int8	159                       # DW_OP_stack_value
 
 
-
-
 source_filename = "stackified.c"
 target triple = "wasm32-unknown-unknown"
 
@@ -57,10 +55,25 @@
   ret void, !dbg !22
 }
 
-declare i32 @input()
+; DebugFixup pass adds a DBG_VALUE instruction to clear the debug value range of
+; "myvar" (!27) after BR_IF instruction in the entry BB. Even though it is
+; generally not allowed to have more instructions after a terminator, this
+; special case should not crash MachineVerifier.
+define void @dbg_value_after_terminator(i32 %a, i32 %b) !dbg !23 {
+entry:
+  %cmp = icmp ne i32 %a, %b, !dbg !25
+  call void @llvm.dbg.value(metadata i1 %cmp, metadata !27, metadata !DIExpression(DW_OP_LLVM_convert, 1, DW_ATE_unsigned, DW_OP_LLVM_convert, 8, DW_ATE_unsigned, DW_OP_stack_value)), !dbg !25
+  br i1 %cmp, label %bb.1, label %bb.0, !dbg !25
 
-declare !dbg !4 void @output(i32, i32)
+bb.0:                                             ; preds = %entry
+  unreachable
 
+bb.1:                                             ; preds = %entry
+  ret void
+}
+
+declare i32 @input()
+declare !dbg !4 void @output(i32, i32)
 declare void @llvm.dbg.value(metadata, metadata, metadata)
 
 !llvm.dbg.cu = !{!0}
@@ -90,3 +103,9 @@
 !20 = !DILocation(line: 5, column: 11, scope: !12)
 !21 = !DILocation(line: 6, column: 3, scope: !12)
 !22 = !DILocation(line: 7, column: 1, scope: !12)
+!23 = distinct !DISubprogram(name: "dbg_value_after_terminator", scope: null, type: !24, spFlags: DISPFlagDefinition, unit: !0)
+!24 = !DISubroutineType(types: !2)
+!25 = !DILocation(line: 0, scope: !26)
+!26 = distinct !DILexicalBlock(scope: !23)
+!27 = !DILocalVariable(name: "myvar", scope: !26, type: !28)
+!28 = !DIBasicType(name: "bool", size: 8, encoding: DW_ATE_boolean)
Index: llvm/lib/CodeGen/MachineVerifier.cpp
===================================================================
--- llvm/lib/CodeGen/MachineVerifier.cpp
+++ llvm/lib/CodeGen/MachineVerifier.cpp
@@ -794,6 +794,18 @@
     lastIndex = idx;
   }
 
+  // WebAssemblyDebugFixup pass can generate a DBG_VALUE instruction after a
+  // terminator, in case the terminator instruction consumes a stack operand.
+  // Consuming a stack operand changes the contents of the stack, so a DBG_VALUE
+  // instruction is necessary to terminate the associated variable's range.
+  // The DBG_VALUE instruction takes a form of
+  // DBG_VALUE $noreg, $noreg, !"variable", ...
+  if (TM->getTargetTriple().isWasm() && FirstTerminator && MI->isDebugValue() &&
+      MI->getOperand(0).isReg() && MI->getOperand(1).isReg() &&
+      !MI->getOperand(0).getReg().isValid() &&
+      !MI->getOperand(1).getReg().isValid())
+    return;
+
   // Ensure non-terminators don't follow terminators.
   if (MI->isTerminator()) {
     if (!FirstTerminator)


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