[DEBUGINFO] 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. 

Reviewers: aprantl, NicolaPrica

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

llvm-svn: 352642

1 files changed, 53 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/MachineInstr.cpp b/llvm/lib/CodeGen/MachineInstr.cpp
index 7ab17fce04d..fa3f7874b12 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"
@@ -2100,3 +2101,54 @@ 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;
+}