[MI] Change the array of `MachineMemOperand` pointers to be

a generically extensible collection of extra info attached to
a `MachineInstr`.

The primary change here is cleaning up the APIs used for setting and
manipulating the `MachineMemOperand` pointer arrays so chat we can
change how they are allocated.

Then we introduce an extra info object that using the trailing object
pattern to attach some number of MMOs but also other extra info. The
design of this is specifically so that this extra info has a fixed
necessary cost (the header tracking what extra info is included) and
everything else can be tail allocated. This pattern works especially
well with a `BumpPtrAllocator` which we use here.

I've also added the basic scaffolding for putting interesting pointers
into this, namely pre- and post-instruction symbols. These aren't used
anywhere yet, they're just there to ensure I've actually gotten the data
structure types correct. I'll flesh out support for these in
a subsequent patch (MIR dumping, parsing, the works).

Finally, I've included an optimization where we store any single pointer
inline in the `MachineInstr` to avoid the allocation overhead. This is
expected to be the overwhelmingly most common case and so should avoid
any memory usage growth due to slightly less clever / dense allocation
when dealing with >1 MMO. This did require several ergonomic
improvements to the `PointerSumType` to reasonably support the various
usage models.

This also has a side effect of freeing up 8 bits within the
`MachineInstr` which could be repurposed for something else.

The suggested direction here came largely from Hal Finkel. I hope it was
worth it. ;] It does hopefully clear a path for subsequent extensions
w/o nearly as much leg work. Lots of thanks to Reid and Justin for
careful reviews and ideas about how to do all of this.

Differential Revision: https://reviews.llvm.org/D50701

llvm-svn: 339940

1 files changed, 6 insertions, 71 deletions

diff --git a/llvm/lib/CodeGen/MachineFunction.cpp b/llvm/lib/CodeGen/MachineFunction.cpp
index dd668bc..1b15819c 100644
--- a/llvm/lib/CodeGen/MachineFunction.cpp
+++ b/llvm/lib/CodeGen/MachineFunction.cpp
@@ -406,77 +406,12 @@ MachineFunction::getMachineMemOperand(const MachineMemOperand *MMO,
                                MMO->getOrdering(), MMO->getFailureOrdering());
 }
 
-MachineInstr::mmo_iterator
-MachineFunction::allocateMemRefsArray(unsigned long Num) {
-  return Allocator.Allocate<MachineMemOperand *>(Num);
-}
-
-std::pair<MachineInstr::mmo_iterator, MachineInstr::mmo_iterator>
-MachineFunction::extractLoadMemRefs(MachineInstr::mmo_iterator Begin,
-                                    MachineInstr::mmo_iterator End) {
-  // Count the number of load mem refs.
-  unsigned Num = 0;
-  for (MachineInstr::mmo_iterator I = Begin; I != End; ++I)
-    if ((*I)->isLoad())
-      ++Num;
-
-  // Allocate a new array and populate it with the load information.
-  MachineInstr::mmo_iterator Result = allocateMemRefsArray(Num);
-  unsigned Index = 0;
-  for (MachineInstr::mmo_iterator I = Begin; I != End; ++I) {
-    if ((*I)->isLoad()) {
-      if (!(*I)->isStore())
-        // Reuse the MMO.
-        Result[Index] = *I;
-      else {
-        // Clone the MMO and unset the store flag.
-        MachineMemOperand *JustLoad =
-          getMachineMemOperand((*I)->getPointerInfo(),
-                               (*I)->getFlags() & ~MachineMemOperand::MOStore,
-                               (*I)->getSize(), (*I)->getBaseAlignment(),
-                               (*I)->getAAInfo(), nullptr,
-                               (*I)->getSyncScopeID(), (*I)->getOrdering(),
-                               (*I)->getFailureOrdering());
-        Result[Index] = JustLoad;
-      }
-      ++Index;
-    }
-  }
-  return std::make_pair(Result, Result + Num);
-}
-
-std::pair<MachineInstr::mmo_iterator, MachineInstr::mmo_iterator>
-MachineFunction::extractStoreMemRefs(MachineInstr::mmo_iterator Begin,
-                                     MachineInstr::mmo_iterator End) {
-  // Count the number of load mem refs.
-  unsigned Num = 0;
-  for (MachineInstr::mmo_iterator I = Begin; I != End; ++I)
-    if ((*I)->isStore())
-      ++Num;
-
-  // Allocate a new array and populate it with the store information.
-  MachineInstr::mmo_iterator Result = allocateMemRefsArray(Num);
-  unsigned Index = 0;
-  for (MachineInstr::mmo_iterator I = Begin; I != End; ++I) {
-    if ((*I)->isStore()) {
-      if (!(*I)->isLoad())
-        // Reuse the MMO.
-        Result[Index] = *I;
-      else {
-        // Clone the MMO and unset the load flag.
-        MachineMemOperand *JustStore =
-          getMachineMemOperand((*I)->getPointerInfo(),
-                               (*I)->getFlags() & ~MachineMemOperand::MOLoad,
-                               (*I)->getSize(), (*I)->getBaseAlignment(),
-                               (*I)->getAAInfo(), nullptr,
-                               (*I)->getSyncScopeID(), (*I)->getOrdering(),
-                               (*I)->getFailureOrdering());
-        Result[Index] = JustStore;
-      }
-      ++Index;
-    }
-  }
-  return std::make_pair(Result, Result + Num);
+MachineInstr::ExtraInfo *
+MachineFunction::createMIExtraInfo(ArrayRef<MachineMemOperand *> MMOs,
+                                   MCSymbol *PreInstrSymbol,
+                                   MCSymbol *PostInstrSymbol) {
+  return MachineInstr::ExtraInfo::create(Allocator, MMOs, PreInstrSymbol,
+                                         PostInstrSymbol);
 }
 
 const char *MachineFunction::createExternalSymbolName(StringRef Name) {