[MC] Fix constant pools with DenseMap sentinel values

[olista01]

Summary

The MC ConstantPool class uses a DenseMap to track generated constants, with the int64_t value of the constant as the key. This fails when values of 0x7fffffffffffffff or0x7ffffffffffffffe are inserted into the constant pool, as these are sentinel values for DenseMap.

The fix is to use std::map instead, which doesn't use sentinel values.

[SjoerdMeijer]

Looks good to me.

llvm/trunk/include/llvm/MC/ConstantPools.h

 #ifndef LLVM_MC_CONSTANTPOOLS_H
 #define LLVM_MC_CONSTANTPOOLS_H
 
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/MapVector.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/Support/SMLoc.h"
 #include <cstdint>
+#include <map>
 
 namespace llvm {
 
 class MCContext;
 class MCExpr;
 class MCSection;
 class MCStreamer;
 class MCSymbol;
struct ConstantPoolEntry {
   SMLoc Loc;
 };
 
 // A class to keep track of assembler-generated constant pools that are use to
 // implement the ldr-pseudo.
 class ConstantPool {
   using EntryVecTy = SmallVector<ConstantPoolEntry, 4>;
   EntryVecTy Entries;
-  DenseMap<int64_t, const MCSymbolRefExpr *> CachedEntries;
+  std::map<int64_t, const MCSymbolRefExpr *> CachedEntries;
 
 public:
   // Initialize a new empty constant pool
   ConstantPool() = default;
 
   // Add a new entry to the constant pool in the next slot.
   // \param Value is the new entry to put in the constant pool.
   // \param Size is the size in bytes of the entry

llvm/trunk/test/MC/AArch64/ldr-pseudo.s

 // CHECK-LABEL: f18:
 f18:
   ldr w0, =0x320064
 // CHECK: ldr w0, .Ltmp[[TMP25:[0-9]+]]
   add w0, w0, #1
   ldr x1, =0x320064
 // CHECK: ldr x1, .Ltmp[[TMP26:[0-9]+]]
 
+// We previously used a DenseMap with constant values as keys, check that
+// sentinel values can be used.
+  ldr x0, =0x7ffffffffffffffe
+// CHECK: ldr x0, .Ltmp[[TMP27:[0-9]+]]
+  ldr x1, =0x7fffffffffffffff
+// CHECK: ldr x1, .Ltmp[[TMP28:[0-9]+]]
+
 //
 // Constant Pools
 //
 // CHECK: .section b,"ax",@progbits
 // CHECK: .p2align 2
 // CHECK: .Ltmp[[TMP0]]
 // CHECK: .word 65537
 

 // CHECK: .p2align 2
 // CHECK: .Ltmp[[TMP24]]
 // CHECK: .word -1
 
 // CHECK: .section o,"ax",@progbits
 // CHECK: .p2align 2
 // CHECK: .Ltmp[[TMP25]]
 // CHECK: .word 3276900
+
+// CHECK: .Ltmp[[TMP27]]
+// CHECK: .xword 9223372036854775806
+// CHECK: .Ltmp[[TMP28]]
+// CHECK: .xword 9223372036854775807