From ffba94a9acff76e51ce64c331b500f7b1a44840f Mon Sep 17 00:00:00 2001
From: Vedant Kumar <vsk@apple.com>
Date: Wed, 28 Oct 2020 18:55:46 -0700
Subject: [PATCH] Revert "[DebugInfo] Fix legacy ZExt emission when FromBits >=
 64 (PR47927)"

This reverts commit 99053462216cf835eb3ae063942c618d9609de87.

It breaks the compiler-rt build, see https://reviews.llvm.org/D89838
---
 llvm/lib/CodeGen/AsmPrinter/DwarfExpression.cpp | 18 +++++---------
 llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h   |  2 +-
 llvm/test/DebugInfo/X86/legacy-zext.ll          | 32 -------------------------
 3 files changed, 7 insertions(+), 45 deletions(-)
 delete mode 100644 llvm/test/DebugInfo/X86/legacy-zext.ll

diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.cpp
index c707113..f256098 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.cpp
@@ -562,7 +562,7 @@ void DwarfExpression::addExpression(DIExpressionCursor &&ExprCursor,
           if (Encoding == dwarf::DW_ATE_signed)
             emitLegacySExt(PrevConvertOp->getArg(0));
           else if (Encoding == dwarf::DW_ATE_unsigned)
-            emitLegacyZExt(PrevConvertOp->getArg(0), BitSize);
+            emitLegacyZExt(PrevConvertOp->getArg(0));
           PrevConvertOp = None;
         } else {
           PrevConvertOp = Op;
@@ -654,17 +654,11 @@ void DwarfExpression::emitLegacySExt(unsigned FromBits) {
   emitOp(dwarf::DW_OP_or);
 }
 
-void DwarfExpression::emitLegacyZExt(unsigned FromBits, unsigned ToBits) {
-  if (FromBits < 64) {
-    // X & ((1 << FromBits) - 1)
-    emitOp(dwarf::DW_OP_constu);
-    emitUnsigned((1ULL << FromBits) - 1);
-    emitOp(dwarf::DW_OP_and);
-  } else {
-    addOpPiece(FromBits, 0);
-    emitOp(dwarf::DW_OP_lit0);
-    addOpPiece(ToBits - FromBits, FromBits);
-  }
+void DwarfExpression::emitLegacyZExt(unsigned FromBits) {
+  // (X & (1 << FromBits - 1))
+  emitOp(dwarf::DW_OP_constu);
+  emitUnsigned((1ULL << FromBits) - 1);
+  emitOp(dwarf::DW_OP_and);
 }
 
 void DwarfExpression::addWasmLocation(unsigned Index, uint64_t Offset) {
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h b/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h
index 46b9db2..78a98a6 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h
@@ -351,7 +351,7 @@ public:
   void addFragmentOffset(const DIExpression *Expr);
 
   void emitLegacySExt(unsigned FromBits);
-  void emitLegacyZExt(unsigned FromBits, unsigned ToBits);
+  void emitLegacyZExt(unsigned FromBits);
 
   /// Emit location information expressed via WebAssembly location + offset
   /// The Index is an identifier for locals, globals or operand stack.
diff --git a/llvm/test/DebugInfo/X86/legacy-zext.ll b/llvm/test/DebugInfo/X86/legacy-zext.ll
deleted file mode 100644
index 4c1bd78..0000000
--- a/llvm/test/DebugInfo/X86/legacy-zext.ll
+++ /dev/null
@@ -1,32 +0,0 @@
-; RUN: llc -filetype=obj -o - %s | llvm-dwarfdump - | FileCheck %s
-
-; CHECK: DW_AT_location (DW_OP_breg5 RDI+0, DW_OP_piece 0x8, DW_OP_lit0, DW_OP_bit_piece 0x40 0x40)
-
-target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
-target triple = "x86_64-unknown-linux-gnu"
-
-define void @t(i64 %x) !dbg !6 {
-  call void @llvm.dbg.value(metadata i64 %x, metadata !9,
-                            metadata !DIExpression(DW_OP_LLVM_convert, 64, DW_ATE_unsigned,
-                                                   DW_OP_LLVM_convert, 128, DW_ATE_unsigned)), !dbg !11
-  ret void, !dbg !11
-}
-
-declare void @llvm.dbg.value(metadata, metadata, metadata)
-
-!llvm.dbg.cu = !{!0}
-!llvm.debugify = !{!3, !4}
-!llvm.module.flags = !{!5}
-
-!0 = distinct !DICompileUnit(language: DW_LANG_C, file: !1, producer: "debugify", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2)
-!1 = !DIFile(filename: "legacy-zext.ll", directory: "/")
-!2 = !{}
-!3 = !{i64 2}
-!4 = !{i64 1}
-!5 = !{i64 2, !"Debug Info Version", i32 3}
-!6 = distinct !DISubprogram(name: "t", linkageName: "t", scope: null, file: !1, line: 1, type: !7, scopeLine: 1, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !8)
-!7 = !DISubroutineType(types: !2)
-!8 = !{!9}
-!9 = !DILocalVariable(name: "1", scope: !6, file: !1, line: 1, type: !10)
-!10 = !DIBasicType(name: "ty128", size: 128, encoding: DW_ATE_unsigned)
-!11 = !DILocation(line: 1, column: 1, scope: !6)
-- 
2.7.4