diff --git a/llvm/include/llvm/CodeGen/TargetInstrInfo.h b/llvm/include/llvm/CodeGen/TargetInstrInfo.h
index 3910e77d13de7..d629d7fd18071 100644
--- a/llvm/include/llvm/CodeGen/TargetInstrInfo.h
+++ b/llvm/include/llvm/CodeGen/TargetInstrInfo.h
@@ -428,6 +428,22 @@ class LLVM_ABI TargetInstrInfo : public MCInstrInfo {
     return ~0U;
   }
 
+  enum class InstSizeVerifyMode {
+    /// Do not verify instruction size.
+    NoVerify,
+    /// Check that the instruction size matches exactly.
+    ExactSize,
+    /// Allow the reported instruction size to be larger than the actual size.
+    AllowOverEstimate,
+  };
+
+  /// Determine whether/how the instruction size returned by
+  /// getInstSizeInBytes() should be verified.
+  virtual InstSizeVerifyMode
+  getInstSizeVerifyMode(const MachineInstr &MI) const {
+    return InstSizeVerifyMode::NoVerify;
+  }
+
   /// Return true if the instruction is as cheap as a move instruction.
   ///
   /// Targets for different archs need to override this, and different
diff --git a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
index db4fc5888f6d4..ea4908b205241 100644
--- a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
@@ -2147,6 +2147,11 @@ void AsmPrinter::emitFunctionBody() {
       if (isVerbose())
         emitComments(MI, STI, OutStreamer->getCommentOS());
 
+#ifndef NDEBUG
+      MCFragment *OldFragment = OutStreamer->getCurrentFragment();
+      size_t OldFragSize = OldFragment->getFixedSize();
+#endif
+
       switch (MI.getOpcode()) {
       case TargetOpcode::CFI_INSTRUCTION:
         emitCFIInstruction(MI);
@@ -2265,6 +2270,36 @@ void AsmPrinter::emitFunctionBody() {
         break;
       }
 
+#ifndef NDEBUG
+      // Verify that the instruction size reported by InstrInfo matches the
+      // actually emitted size. Many backends performing branch relaxation
+      // on the MIR level rely on this for correctness.
+      if (OutStreamer->isObj()) {
+        const TargetInstrInfo *TII = MF->getSubtarget().getInstrInfo();
+        MCFragment *NewFragment = OutStreamer->getCurrentFragment();
+        TargetInstrInfo::InstSizeVerifyMode Mode =
+            TII->getInstSizeVerifyMode(MI);
+        // Don't try to handle fragment splitting cases.
+        if (NewFragment == OldFragment &&
+            Mode != TargetInstrInfo::InstSizeVerifyMode::NoVerify) {
+          unsigned ExpectedSize = TII->getInstSizeInBytes(MI);
+          unsigned ActualSize = NewFragment->getFixedSize() - OldFragSize;
+          bool AllowOverEstimate =
+              Mode == TargetInstrInfo::InstSizeVerifyMode::AllowOverEstimate;
+          bool Valid = AllowOverEstimate ? ActualSize <= ExpectedSize
+                                         : ActualSize == ExpectedSize;
+          if (!Valid) {
+            dbgs() << "In function: " << MF->getName() << "\n";
+            dbgs() << "Size mismatch for: " << MI;
+            dbgs() << "Expected " << (AllowOverEstimate ? "maximum" : "exact")
+                   << " size: " << ExpectedSize << "\n";
+            dbgs() << "Actual size: " << ActualSize << "\n";
+            abort();
+          }
+        }
+      }
+#endif
+
       if (MI.isCall()) {
         if (MF->getTarget().Options.BBAddrMap)
           OutStreamer->emitLabel(createCallsiteEndSymbol(MBB));
diff --git a/llvm/lib/Target/PowerPC/PPCAsmPrinter.cpp b/llvm/lib/Target/PowerPC/PPCAsmPrinter.cpp
index f5d56c1e8e264..6d1ee6bb111fe 100644
--- a/llvm/lib/Target/PowerPC/PPCAsmPrinter.cpp
+++ b/llvm/lib/Target/PowerPC/PPCAsmPrinter.cpp
@@ -27,7 +27,6 @@
 #include "PPCTargetMachine.h"
 #include "TargetInfo/PowerPCTargetInfo.h"
 #include "llvm/ADT/MapVector.h"
-#include "llvm/ADT/ScopeExit.h"
 #include "llvm/ADT/SetVector.h"
 #include "llvm/ADT/Statistic.h"
 #include "llvm/ADT/StringExtras.h"
@@ -946,31 +945,6 @@ void PPCAsmPrinter::emitInstruction(const MachineInstr *MI) {
     return PPC::S_None;
   };
 
-#ifndef NDEBUG
-  // Instruction sizes must be correct for PPCBranchSelector to pick the
-  // right branch kind. Verify that the reported sizes and the actually
-  // emitted sizes match.
-  unsigned ExpectedSize = Subtarget->getInstrInfo()->getInstSizeInBytes(*MI);
-  MCFragment *OldFragment = OutStreamer->getCurrentFragment();
-  size_t OldFragSize = OldFragment->getFixedSize();
-  scope_exit VerifyInstSize([&]() {
-    if (!OutStreamer->isObj())
-      return; // Can only verify size when streaming to object.
-    MCFragment *NewFragment = OutStreamer->getCurrentFragment();
-    if (NewFragment != OldFragment)
-      return; // Don't try to handle fragment splitting cases.
-    unsigned ActualSize = NewFragment->getFixedSize() - OldFragSize;
-    // FIXME: InstrInfo currently over-estimates the size of STACKMAP.
-    if (ActualSize != ExpectedSize &&
-        MI->getOpcode() != TargetOpcode::STACKMAP) {
-      dbgs() << "Size mismatch for: " << *MI << "\n";
-      dbgs() << "Expected size: " << ExpectedSize << "\n";
-      dbgs() << "Actual size: " << ActualSize << "\n";
-      abort();
-    }
-  });
-#endif
-
   // Lower multi-instruction pseudo operations.
   switch (MI->getOpcode()) {
   default: break;
diff --git a/llvm/lib/Target/PowerPC/PPCInstrInfo.cpp b/llvm/lib/Target/PowerPC/PPCInstrInfo.cpp
index 278fd37d4c229..d1c7bfde4d506 100644
--- a/llvm/lib/Target/PowerPC/PPCInstrInfo.cpp
+++ b/llvm/lib/Target/PowerPC/PPCInstrInfo.cpp
@@ -3034,6 +3034,14 @@ unsigned PPCInstrInfo::getInstSizeInBytes(const MachineInstr &MI) const {
   }
 }
 
+TargetInstrInfo::InstSizeVerifyMode
+PPCInstrInfo::getInstSizeVerifyMode(const MachineInstr &MI) const {
+  // FIXME: The size of STACKMAP is currently over-estimated.
+  return MI.getOpcode() != TargetOpcode::STACKMAP
+             ? InstSizeVerifyMode::AllowOverEstimate
+             : InstSizeVerifyMode::ExactSize;
+}
+
 std::pair<unsigned, unsigned>
 PPCInstrInfo::decomposeMachineOperandsTargetFlags(unsigned TF) const {
   // PPC always uses a direct mask.
diff --git a/llvm/lib/Target/PowerPC/PPCInstrInfo.h b/llvm/lib/Target/PowerPC/PPCInstrInfo.h
index 9fe5706e7b1e0..adfae11d4cac4 100644
--- a/llvm/lib/Target/PowerPC/PPCInstrInfo.h
+++ b/llvm/lib/Target/PowerPC/PPCInstrInfo.h
@@ -700,6 +700,9 @@ class PPCInstrInfo : public PPCGenInstrInfo {
   ///
   unsigned getInstSizeInBytes(const MachineInstr &MI) const override;
 
+  InstSizeVerifyMode
+  getInstSizeVerifyMode(const MachineInstr &MI) const override;
+
   MCInst getNop() const override;
 
   std::pair<unsigned, unsigned>