[DEBUGINFO] Reposting r352642: Handle restore instructions in LiveDebugValues

The LiveDebugValues pass recognizes spills but not restores, which can
cause large gaps in location information for some variables, depending
on control flow. This patch make LiveDebugValues recognize restores and
generate appropriate DBG_VALUE instructions.

This patch was posted previously with r352642 and reverted in r352666 due
to buildbot errors. A missing return statement was the cause for the 
failures.

Reviewers: aprantl, NicolaPrica

Differential Revision: https://reviews.llvm.org/D57271

llvm-svn: 353089

1 files changed, 53 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/MachineInstr.cpp b/llvm/lib/CodeGen/MachineInstr.cpp
index ca43804481b..7ef931a6636 100644
--- a/llvm/lib/CodeGen/MachineInstr.cpp
+++ b/llvm/lib/CodeGen/MachineInstr.cpp
@@ -25,6 +25,7 @@
 #include "llvm/Analysis/MemoryLocation.h"
 #include "llvm/CodeGen/GlobalISel/RegisterBank.h"
 #include "llvm/CodeGen/MachineBasicBlock.h"
+#include "llvm/CodeGen/MachineFrameInfo.h"
 #include "llvm/CodeGen/MachineFunction.h"
 #include "llvm/CodeGen/MachineInstrBuilder.h"
 #include "llvm/CodeGen/MachineInstrBundle.h"
@@ -49,9 +50,9 @@
 #include "llvm/IR/Metadata.h"
 #include "llvm/IR/Module.h"
 #include "llvm/IR/ModuleSlotTracker.h"
+#include "llvm/IR/Operator.h"
 #include "llvm/IR/Type.h"
 #include "llvm/IR/Value.h"
-#include "llvm/IR/Operator.h"
 #include "llvm/MC/MCInstrDesc.h"
 #include "llvm/MC/MCRegisterInfo.h"
 #include "llvm/MC/MCSymbol.h"
@@ -2102,3 +2103,54 @@ void MachineInstr::changeDebugValuesDefReg(unsigned Reg) {
   for (auto *DBI : DbgValues)
     DBI->getOperand(0).setReg(Reg);
 }
+
+using MMOList = SmallVector<const MachineMemOperand *, 2>;
+
+static unsigned getSpillSlotSize(MMOList &Accesses,
+                                 const MachineFrameInfo &MFI) {
+  unsigned Size = 0;
+  for (auto A : Accesses)
+    if (MFI.isSpillSlotObjectIndex(
+            cast<FixedStackPseudoSourceValue>(A->getPseudoValue())
+                ->getFrameIndex()))
+      Size += A->getSize();
+  return Size;
+}
+
+Optional<unsigned>
+MachineInstr::getSpillSize(const TargetInstrInfo *TII) const {
+  int FI;
+  if (TII->isStoreToStackSlotPostFE(*this, FI)) {
+    const MachineFrameInfo &MFI = getMF()->getFrameInfo();
+    if (MFI.isSpillSlotObjectIndex(FI))
+      return (*memoperands_begin())->getSize();
+  }
+  return None;
+}
+
+Optional<unsigned>
+MachineInstr::getFoldedSpillSize(const TargetInstrInfo *TII) const {
+  MMOList Accesses;
+  if (TII->hasStoreToStackSlot(*this, Accesses))
+    return getSpillSlotSize(Accesses, getMF()->getFrameInfo());
+  return None;
+}
+
+Optional<unsigned>
+MachineInstr::getRestoreSize(const TargetInstrInfo *TII) const {
+  int FI;
+  if (TII->isLoadFromStackSlotPostFE(*this, FI)) {
+    const MachineFrameInfo &MFI = getMF()->getFrameInfo();
+    if (MFI.isSpillSlotObjectIndex(FI))
+      return (*memoperands_begin())->getSize();
+  }
+  return None;
+}
+
+Optional<unsigned>
+MachineInstr::getFoldedRestoreSize(const TargetInstrInfo *TII) const {
+  MMOList Accesses;
+  if (TII->hasLoadFromStackSlot(*this, Accesses))
+    return getSpillSlotSize(Accesses, getMF()->getFrameInfo());
+  return None;
+}