[AIX][XCOFF] add symbol priority for the llvm-objdump -D -symbol-description

SUMMARY:
when there are two symbol has the same address. llvm-objdump -D -symbol-description will select symbol based on the following rule:

1. using Label first if there is a Label symbol.
2. If there is not Label, using a symbol which has Storage Mapping class.
3. if more than one symbol has storage mapping class, put the TC0 has the low priority, for other storage mapping class , compare based on the value.

Reviewers: James Henderson ,hubert.reinterpretcast,

Differential Revision: https://reviews.llvm.org/D78387

include/llvm/MC/MCDisassembler/MCDisassembler.h

@@ -26,6 +26,8 @@ struct XCOFFSymbolInfo {
   XCOFFSymbolInfo(Optional<XCOFF::StorageMappingClass> Smc,
                   Optional<uint32_t> Idx, bool Label)
       : StorageMappingClass(Smc), Index(Idx), IsLabel(Label) {}
+
+  bool operator<(const XCOFFSymbolInfo &SymInfo) const;
 };
 
 struct SymbolInfoTy {
@@ -53,8 +55,9 @@ private:
     assert(P1.IsXCOFF == P2.IsXCOFF &&
            "P1.IsXCOFF should be equal to P2.IsXCOFF.");
     if (P1.IsXCOFF)
-      return std::tie(P1.Addr, P1.Name) < std::tie(P2.Addr, P2.Name);
-    else
+      return std::tie(P1.Addr, P1.XCOFFSymInfo, P1.Name) <
+             std::tie(P2.Addr, P2.XCOFFSymInfo, P2.Name);
+
     return std::tie(P1.Addr, P1.Name, P1.Type) <
              std::tie(P2.Addr, P2.Name, P2.Type);
   }

lib/MC/MCDisassembler/MCDisassembler.cpp

@@ -43,3 +43,56 @@ void MCDisassembler::tryAddingPcLoadReferenceComment(int64_t Value,
 void MCDisassembler::setSymbolizer(std::unique_ptr<MCSymbolizer> Symzer) {
   Symbolizer = std::move(Symzer);
 }
+
+#define SMC_PCASE(A, P)                                                         \
+  case XCOFF::XMC_##A:                                                         \
+    return P;
+
+uint8_t getSMCPriority(XCOFF::StorageMappingClass SMC) {
+  switch (SMC) {
+    SMC_PCASE(PR, 1)
+    SMC_PCASE(RO, 1)
+    SMC_PCASE(DB, 1)
+    SMC_PCASE(GL, 1)
+    SMC_PCASE(XO, 1)
+    SMC_PCASE(SV, 1)
+    SMC_PCASE(SV64, 1)
+    SMC_PCASE(SV3264, 1)
+    SMC_PCASE(TI, 1)
+    SMC_PCASE(TB, 1)
+    SMC_PCASE(RW, 1)
+    SMC_PCASE(TC0, 0)
+    SMC_PCASE(TC, 1)
+    SMC_PCASE(TD, 1)
+    SMC_PCASE(DS, 1)
+    SMC_PCASE(UA, 1)
+    SMC_PCASE(BS, 1)
+    SMC_PCASE(UC, 1)
+    SMC_PCASE(TL, 1)
+    SMC_PCASE(UL, 1)
+    SMC_PCASE(TE, 1)
+#undef SMC_PCASE
+  }
+  return 0;
+}
+
+/// The function is for symbol sorting when symbols have the same address.
+/// The symbols in the same section are sorted in ascending order.
+/// llvm-objdump -D will choose the highest priority symbol to display when
+/// there are symbols with the same address.
+bool XCOFFSymbolInfo::operator<(const XCOFFSymbolInfo &SymInfo) const {
+  // Label symbols have higher priority than non-label symbols.
+  if (IsLabel != SymInfo.IsLabel)
+    return SymInfo.IsLabel;
+
+  // Symbols with a StorageMappingClass have higher priority than those without.
+  if (StorageMappingClass.hasValue() != SymInfo.StorageMappingClass.hasValue())
+    return SymInfo.StorageMappingClass.hasValue();
+
+  if (StorageMappingClass.hasValue()) {
+    return getSMCPriority(StorageMappingClass.getValue()) <
+           getSMCPriority(SymInfo.StorageMappingClass.getValue());
+  }
+
+  return false;
+}

test/tools/llvm-objdump/XCOFF/disassemble-symbol-description.test

@@ -25,7 +25,7 @@
 COMMON: Inputs/xcoff-section-headers.o:	file format aixcoff-rs6000
 COMMON: Disassembly of section .text:
 PLAIN:      00000000 <.text>:
-DESC:       00000000 (idx: 4) .text:
+DESC:       00000000 (idx: 16) .func: 
 COMMON-NEXT:        0: 80 62 00 04                  	lwz 3, 4(2)
 RELOC:                              00000002:  R_TOC        (idx: 26) a[TC]
 COMMON-NEXT:        4: 80 63 00 00                  	lwz 3, 0(3)

unittests/MC/CMakeLists.txt

@@ -17,5 +17,6 @@ add_llvm_unittest(MCTests
   MCInstPrinter.cpp
   StringTableBuilderTest.cpp
   TargetRegistry.cpp
+  MCDisassemblerTest.cpp
   )
 

unittests/MC/MCDisassemblerTest.cpp

@@ -0,0 +1,49 @@
+//===- MCDisassemblerTest.cpp - Tests for MCDisassembler.cpp --------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/MC/MCDisassembler/MCDisassembler.h"
+#include "gtest/gtest.h"
+
+using namespace llvm;
+
+TEST(MCDisassembler, XCOFFSymbolPriorityTest) {
+
+  SymbolInfoTy SIT1(0x100000, "sym1", None, 1, false);
+  SymbolInfoTy SIT2(0x110000, "sym2", None, 2, false);
+  SymbolInfoTy SIT3(0x120000, ".func", XCOFF::XMC_PR, 3, true);
+  SymbolInfoTy SIT4(0x120000, ".text", XCOFF::XMC_PR, 4, false);
+  SymbolInfoTy SIT5(0x130000, "TOC", XCOFF::XMC_TC0, 5, false);
+  SymbolInfoTy SIT6(0x130000, "func", XCOFF::XMC_TC, 6, false);
+
+  // Test that higher addresses would appear later than lower ones when symbols
+  // are sorted in ascending order.
+  EXPECT_TRUE(SIT1 < SIT2);
+  EXPECT_FALSE(SIT2 < SIT1);
+
+  // Test that symbols with a StorageMappingClass have higher priority than those
+  // without.
+  EXPECT_TRUE(SIT2 < SIT5);
+  EXPECT_FALSE(SIT5 < SIT2);
+
+  // Test that symbols with a TC0 StorageMappingClass have lower priority than those
+  // with some other StorageMappingClass.
+  EXPECT_TRUE(SIT5 < SIT6);
+  EXPECT_FALSE(SIT6 < SIT5);
+
+  // Test label symbols have higher priorty than non-label symbols.
+  EXPECT_TRUE(SIT4 < SIT3);
+  EXPECT_FALSE(SIT3 < SIT4);
+
+  // Test symbols comparing with themselves.
+  EXPECT_FALSE(SIT1 < SIT1);
+  EXPECT_FALSE(SIT2 < SIT2);
+  EXPECT_FALSE(SIT3 < SIT3);
+  EXPECT_FALSE(SIT4 < SIT4);
+  EXPECT_FALSE(SIT5 < SIT5);
+  EXPECT_FALSE(SIT6 < SIT6);
+}