Revert "Encode address offsets of basic blocks relative to the end of the previous basic blocks."

This reverts commit 029283c1c0.
The code in `ELFFile::decodeBBAddrMap` was not changed in the submitted patch.

Differential Revision: https://reviews.llvm.org/D120457

llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp

@@ -1152,19 +1152,16 @@ void AsmPrinter::emitBBAddrMapSection(const MachineFunction &MF) {
   OutStreamer->emitSymbolValue(FunctionSymbol, getPointerSize());
   // Emit the total number of basic blocks in this function.
   OutStreamer->emitULEB128IntValue(MF.size());
-  const MCSymbol *PrevMBBEndSymbol = FunctionSymbol;
   // Emit BB Information for each basic block in the funciton.
   for (const MachineBasicBlock &MBB : MF) {
     const MCSymbol *MBBSymbol =
         MBB.isEntryBlock() ? FunctionSymbol : MBB.getSymbol();
-    // Emit the basic block offset relative to the end of the previous block.
-    // This is zero unless the block is padded due to alignment.
-    emitLabelDifferenceAsULEB128(MBBSymbol, PrevMBBEndSymbol);
+    // Emit the basic block offset.
+    emitLabelDifferenceAsULEB128(MBBSymbol, FunctionSymbol);
     // Emit the basic block size. When BBs have alignments, their size cannot
     // always be computed from their offsets.
     emitLabelDifferenceAsULEB128(MBB.getEndSymbol(), MBBSymbol);
     OutStreamer->emitULEB128IntValue(getBBAddrMapMetadata(MBB));
-    PrevMBBEndSymbol = MBB.getEndSymbol();
   }
   OutStreamer->PopSection();
 }

llvm/lib/CodeGen/BasicBlockSections.cpp

@@ -60,7 +60,7 @@
 // Basic Block Labels
 // ==================
 //
-// With -fbasic-block-sections=labels, we encode the offsets of BB addresses of
+// With -fbasic-block-sections=labels, we emit the offsets of BB addresses of
 // every function into the .llvm_bb_addr_map section. Along with the function
 // symbols, this allows for mapping of virtual addresses in PMU profiles back to
 // the corresponding basic blocks. This logic is implemented in AsmPrinter. This

llvm/test/CodeGen/X86/basic-block-sections-labels.ll

@@ -51,12 +51,12 @@ declare i32 @__gxx_personality_v0(...)
 ; CHECK-NEXT:	.uleb128 .Lfunc_begin0-.Lfunc_begin0
 ; CHECK-NEXT:	.uleb128 .LBB_END0_0-.Lfunc_begin0
 ; CHECK-NEXT:	.byte	8
-; CHECK-NEXT:	.uleb128 .LBB0_1-.LBB_END0_0
+; CHECK-NEXT:	.uleb128 .LBB0_1-.Lfunc_begin0
 ; CHECK-NEXT:	.uleb128 .LBB_END0_1-.LBB0_1
 ; CHECK-NEXT:	.byte	8
-; CHECK-NEXT:	.uleb128 .LBB0_2-.LBB_END0_1
+; CHECK-NEXT:	.uleb128 .LBB0_2-.Lfunc_begin0
 ; CHECK-NEXT:	.uleb128 .LBB_END0_2-.LBB0_2
 ; CHECK-NEXT:	.byte	1
-; CHECK-NEXT:	.uleb128 .LBB0_3-.LBB_END0_2
+; CHECK-NEXT:	.uleb128 .LBB0_3-.Lfunc_begin0
 ; CHECK-NEXT:	.uleb128 .LBB_END0_3-.LBB0_3
 ; CHECK-NEXT:	.byte	5

llvm/test/tools/llvm-readobj/ELF/bb-addr-map.test

@@ -30,7 +30,7 @@
 # LLVM-NEXT:         CanFallThrough: No
 # LLVM-NEXT:       }
 # LLVM-NEXT:       {
-# LLVM-NEXT:         Offset: 0x4
+# LLVM-NEXT:         Offset: 0x3
 # LLVM-NEXT:         Size: 0x4
 # LLVM-NEXT:         HasReturn: Yes
 # LLVM-NEXT:         HasTailCall: No

llvm/tools/llvm-readobj/ELFDumper.cpp

@@ -6983,13 +6983,10 @@ template <class ELFT> void LLVMELFDumper<ELFT>::printBBAddrMaps() {
       W.printString("Name", FuncName);
 
       ListScope L(W, "BB entries");
-      uint32_t FunctionRelativeAddress = 0;
       for (const BBAddrMap::BBEntry &BBE : AM.BBEntries) {
         DictScope L(W);
-        FunctionRelativeAddress += BBE.Offset;
-        W.printHex("Offset", FunctionRelativeAddress);
+        W.printHex("Offset", BBE.Offset);
         W.printHex("Size", BBE.Size);
-        FunctionRelativeAddress += BBE.Size;
         W.printBoolean("HasReturn", BBE.HasReturn);
         W.printBoolean("HasTailCall", BBE.HasTailCall);
         W.printBoolean("IsEHPad", BBE.IsEHPad);