[PATCH] D15913: Consolidate MemRefs handling from BranchFolding and correct latent bug
Philip Reames via llvm-commits
llvm-commits at lists.llvm.org
Wed Jan 6 11:36:47 PST 2016
This revision was automatically updated to reflect the committed changes.
Closed by commit rL256966: Consolidate MemRefs handling from BranchFolding and correct latent bug (authored by reames).
Changed prior to commit:
http://reviews.llvm.org/D15913?vs=44087&id=44140#toc
Repository:
rL LLVM
http://reviews.llvm.org/D15913
Files:
llvm/trunk/lib/CodeGen/BranchFolding.cpp
llvm/trunk/lib/CodeGen/MachineInstr.cpp
Index: llvm/trunk/lib/CodeGen/BranchFolding.cpp
===================================================================
--- llvm/trunk/lib/CodeGen/BranchFolding.cpp
+++ llvm/trunk/lib/CodeGen/BranchFolding.cpp
@@ -744,18 +744,6 @@
return true;
}
-static bool hasIdenticalMMOs(const MachineInstr *MI1, const MachineInstr *MI2) {
- auto I1 = MI1->memoperands_begin(), E1 = MI1->memoperands_end();
- auto I2 = MI2->memoperands_begin(), E2 = MI2->memoperands_end();
- if ((E1 - I1) != (E2 - I2))
- return false;
- for (; I1 != E1; ++I1, ++I2) {
- if (**I1 != **I2)
- return false;
- }
- return true;
-}
-
static void
removeMMOsFromMemoryOperations(MachineBasicBlock::iterator MBBIStartPos,
MachineBasicBlock &MBBCommon) {
@@ -792,8 +780,7 @@
assert(MBBICommon->isIdenticalTo(&*MBBI) && "Expected matching MIIs!");
if (MBBICommon->mayLoad() || MBBICommon->mayStore())
- if (!hasIdenticalMMOs(&*MBBI, &*MBBICommon))
- MBBICommon->dropMemRefs();
+ MBBICommon->setMemRefs(MBBI->mergeMemRefsWith(*MBBI));
++MBBI;
++MBBICommon;
Index: llvm/trunk/lib/CodeGen/MachineInstr.cpp
===================================================================
--- llvm/trunk/lib/CodeGen/MachineInstr.cpp
+++ llvm/trunk/lib/CodeGen/MachineInstr.cpp
@@ -866,14 +866,44 @@
setMemRefs(NewMemRefs, NewMemRefs + NewNum);
}
+/// Check to see if the MMOs pointed to by the two MemRefs arrays are
+/// identical.
+static bool hasIdenticalMMOs(const MachineInstr &MI1, const MachineInstr &MI2) {
+ auto I1 = MI1.memoperands_begin(), E1 = MI1.memoperands_end();
+ auto I2 = MI2.memoperands_begin(), E2 = MI2.memoperands_end();
+ if ((E1 - I1) != (E2 - I2))
+ return false;
+ for (; I1 != E1; ++I1, ++I2) {
+ if (**I1 != **I2)
+ return false;
+ }
+ return true;
+}
+
std::pair<MachineInstr::mmo_iterator, unsigned>
MachineInstr::mergeMemRefsWith(const MachineInstr& Other) {
- // TODO: If we end up with too many memory operands, return the empty
- // conservative set rather than failing asserts.
+
+ // If either of the incoming memrefs are empty, we must be conservative and
+ // treat this as if we've exhausted our space for memrefs and dropped them.
+ if (memoperands_empty() || Other.memoperands_empty())
+ return std::make_pair(nullptr, 0);
+
+ // If both instructions have identical memrefs, we don't need to merge them.
+ // Since many instructions have a single memref, and we tend to merge things
+ // like pairs of loads from the same location, this catches a large number of
+ // cases in practice.
+ if (hasIdenticalMMOs(*this, Other))
+ return std::make_pair(MemRefs, NumMemRefs);
+
// TODO: consider uniquing elements within the operand lists to reduce
// space usage and fall back to conservative information less often.
- size_t CombinedNumMemRefs = (memoperands_end() - memoperands_begin())
- + (Other.memoperands_end() - Other.memoperands_begin());
+ size_t CombinedNumMemRefs = NumMemRefs + Other.NumMemRefs;
+
+ // If we don't have enough room to store this many memrefs, be conservative
+ // and drop them. Otherwise, we'd fail asserts when trying to add them to
+ // the new instruction.
+ if (CombinedNumMemRefs != uint8_t(CombinedNumMemRefs))
+ return std::make_pair(nullptr, 0);
MachineFunction *MF = getParent()->getParent();
mmo_iterator MemBegin = MF->allocateMemRefsArray(CombinedNumMemRefs);
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