[llvm] 5932fcc - [InlineCost] Consider the default branch when calculating cost (#77856)

via llvm-commits llvm-commits at lists.llvm.org
Sun Feb 11 02:25:03 PST 2024


Author: Quentin Dian
Date: 2024-02-11T18:24:59+08:00
New Revision: 5932fcc47855fdd209784f38820422d2369b84b2

URL: https://github.com/llvm/llvm-project/commit/5932fcc47855fdd209784f38820422d2369b84b2
DIFF: https://github.com/llvm/llvm-project/commit/5932fcc47855fdd209784f38820422d2369b84b2.diff

LOG: [InlineCost] Consider the default branch when calculating cost  (#77856)

First step in fixing #76772.

This PR considers the default branch as a case branch. This will give
the unreachable default branch fair consideration.

Added: 
    llvm/test/Transforms/Inline/inline-switch-default-2.ll
    llvm/test/Transforms/Inline/inline-switch-default.ll

Modified: 
    llvm/include/llvm/Analysis/InlineModelFeatureMaps.h
    llvm/include/llvm/IR/Instructions.h
    llvm/lib/Analysis/InlineCost.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/include/llvm/Analysis/InlineModelFeatureMaps.h b/llvm/include/llvm/Analysis/InlineModelFeatureMaps.h
index ca9bb7244d6699..d62ec9ce491191 100644
--- a/llvm/include/llvm/Analysis/InlineModelFeatureMaps.h
+++ b/llvm/include/llvm/Analysis/InlineModelFeatureMaps.h
@@ -39,6 +39,8 @@ namespace llvm {
   M(int64_t, {1}, jump_table_penalty, "Accumulation of costs for jump tables") \
   M(int64_t, {1}, case_cluster_penalty,                                        \
     "Accumulation of costs for case clusters")                                 \
+  M(int64_t, {1}, switch_default_dest_penalty,                                 \
+    "Accumulation of costs for switch default destination")                    \
   M(int64_t, {1}, switch_penalty,                                              \
     "Accumulation of costs for switch statements")                             \
   M(int64_t, {1}, unsimplified_common_instructions,                            \

diff  --git a/llvm/include/llvm/IR/Instructions.h b/llvm/include/llvm/IR/Instructions.h
index 4b5a4423b76899..1db4ff2f09bca7 100644
--- a/llvm/include/llvm/IR/Instructions.h
+++ b/llvm/include/llvm/IR/Instructions.h
@@ -49,6 +49,7 @@ class DataLayout;
 class StringRef;
 class Type;
 class Value;
+class UnreachableInst;
 
 //===----------------------------------------------------------------------===//
 //                                AllocaInst Class
@@ -3505,6 +3506,12 @@ class SwitchInst : public Instruction {
     return cast<BasicBlock>(getOperand(1));
   }
 
+  /// Returns true if the default branch must result in immediate undefined
+  /// behavior, false otherwise.
+  bool defaultDestUndefined() const {
+    return isa<UnreachableInst>(getDefaultDest()->getFirstNonPHIOrDbg());
+  }
+
   void setDefaultDest(BasicBlock *DefaultCase) {
     setOperand(1, reinterpret_cast<Value*>(DefaultCase));
   }

diff  --git a/llvm/lib/Analysis/InlineCost.cpp b/llvm/lib/Analysis/InlineCost.cpp
index 5b780b520747cc..e55eaa55f8e947 100644
--- a/llvm/lib/Analysis/InlineCost.cpp
+++ b/llvm/lib/Analysis/InlineCost.cpp
@@ -336,8 +336,8 @@ class CallAnalyzer : public InstVisitor<CallAnalyzer, bool> {
 
   /// Called at the end of processing a switch instruction, with the given
   /// number of case clusters.
-  virtual void onFinalizeSwitch(unsigned JumpTableSize,
-                                unsigned NumCaseCluster) {}
+  virtual void onFinalizeSwitch(unsigned JumpTableSize, unsigned NumCaseCluster,
+                                bool DefaultDestUndefined) {}
 
   /// Called to account for any other instruction not specifically accounted
   /// for.
@@ -699,15 +699,16 @@ class InlineCostCallAnalyzer final : public CallAnalyzer {
                                        CallPenalty));
   }
 
-  void onFinalizeSwitch(unsigned JumpTableSize,
-                        unsigned NumCaseCluster) override {
+  void onFinalizeSwitch(unsigned JumpTableSize, unsigned NumCaseCluster,
+                        bool DefaultDestUndefined) override {
+    if (!DefaultDestUndefined)
+      addCost(2 * InstrCost);
     // If suitable for a jump table, consider the cost for the table size and
     // branch to destination.
     // Maximum valid cost increased in this function.
     if (JumpTableSize) {
       int64_t JTCost =
           static_cast<int64_t>(JumpTableSize) * InstrCost + 4 * InstrCost;
-
       addCost(JTCost);
       return;
     }
@@ -1153,6 +1154,7 @@ class InlineCostFeaturesAnalyzer final : public CallAnalyzer {
   // heuristics in the ML inliner.
   static constexpr int JTCostMultiplier = 4;
   static constexpr int CaseClusterCostMultiplier = 2;
+  static constexpr int SwitchDefaultDestCostMultiplier = 2;
   static constexpr int SwitchCostMultiplier = 2;
 
   // FIXME: These are taken from the heuristic-based cost visitor: we should
@@ -1231,8 +1233,11 @@ class InlineCostFeaturesAnalyzer final : public CallAnalyzer {
     }
   }
 
-  void onFinalizeSwitch(unsigned JumpTableSize,
-                        unsigned NumCaseCluster) override {
+  void onFinalizeSwitch(unsigned JumpTableSize, unsigned NumCaseCluster,
+                        bool DefaultDestUndefined) override {
+    if (!DefaultDestUndefined)
+      increment(InlineCostFeatureIndex::switch_default_dest_penalty,
+                SwitchDefaultDestCostMultiplier * InstrCost);
 
     if (JumpTableSize) {
       int64_t JTCost = static_cast<int64_t>(JumpTableSize) * InstrCost +
@@ -2461,7 +2466,7 @@ bool CallAnalyzer::visitSwitchInst(SwitchInst &SI) {
   unsigned NumCaseCluster =
       TTI.getEstimatedNumberOfCaseClusters(SI, JumpTableSize, PSI, BFI);
 
-  onFinalizeSwitch(JumpTableSize, NumCaseCluster);
+  onFinalizeSwitch(JumpTableSize, NumCaseCluster, SI.defaultDestUndefined());
   return false;
 }
 

diff  --git a/llvm/test/Transforms/Inline/inline-switch-default-2.ll b/llvm/test/Transforms/Inline/inline-switch-default-2.ll
new file mode 100644
index 00000000000000..8d3e24c798df82
--- /dev/null
+++ b/llvm/test/Transforms/Inline/inline-switch-default-2.ll
@@ -0,0 +1,317 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 4
+; RUN: opt %s -S -passes=inline -inline-threshold=21 | FileCheck %s
+
+; Check for scenarios without TTI.
+
+define i64 @foo1(i64 %a) {
+; LOOKUPTABLE-LABEL: define i64 @foo1(
+; LOOKUPTABLE-SAME: i64 [[TMP0:%.*]]) {
+; LOOKUPTABLE-NEXT:    switch i64 [[TMP0]], label [[DEFAULT_BRANCH_I:%.*]] [
+; LOOKUPTABLE-NEXT:      i64 0, label [[BRANCH_0_I:%.*]]
+; LOOKUPTABLE-NEXT:      i64 2, label [[BRANCH_2_I:%.*]]
+; LOOKUPTABLE-NEXT:      i64 4, label [[BRANCH_4_I:%.*]]
+; LOOKUPTABLE-NEXT:      i64 6, label [[BRANCH_6_I:%.*]]
+; LOOKUPTABLE-NEXT:    ]
+; LOOKUPTABLE:       branch_0.i:
+; LOOKUPTABLE-NEXT:    br label [[BAR1_EXIT:%.*]]
+; LOOKUPTABLE:       branch_2.i:
+; LOOKUPTABLE-NEXT:    br label [[BAR1_EXIT]]
+; LOOKUPTABLE:       branch_4.i:
+; LOOKUPTABLE-NEXT:    br label [[BAR1_EXIT]]
+; LOOKUPTABLE:       branch_6.i:
+; LOOKUPTABLE-NEXT:    br label [[BAR1_EXIT]]
+; LOOKUPTABLE:       default_branch.i:
+; LOOKUPTABLE-NEXT:    br label [[BAR1_EXIT]]
+; LOOKUPTABLE:       bar1.exit:
+; LOOKUPTABLE-NEXT:    [[TMP2:%.*]] = phi i64 [ 5, [[BRANCH_0_I]] ], [ 9, [[BRANCH_2_I]] ], [ 2, [[BRANCH_4_I]] ], [ 7, [[BRANCH_6_I]] ], [ 3, [[DEFAULT_BRANCH_I]] ]
+; LOOKUPTABLE-NEXT:    ret i64 [[TMP2]]
+;
+; SWITCH-LABEL: define i64 @foo1(
+; SWITCH-SAME: i64 [[TMP0:%.*]]) {
+; SWITCH-NEXT:    switch i64 [[TMP0]], label [[DEFAULT_BRANCH_I:%.*]] [
+; SWITCH-NEXT:      i64 0, label [[BRANCH_0_I:%.*]]
+; SWITCH-NEXT:      i64 2, label [[BRANCH_2_I:%.*]]
+; SWITCH-NEXT:      i64 4, label [[BRANCH_4_I:%.*]]
+; SWITCH-NEXT:      i64 6, label [[BRANCH_6_I:%.*]]
+; SWITCH-NEXT:    ]
+; SWITCH:       branch_0.i:
+; SWITCH-NEXT:    br label [[BAR1_EXIT:%.*]]
+; SWITCH:       branch_2.i:
+; SWITCH-NEXT:    br label [[BAR1_EXIT]]
+; SWITCH:       branch_4.i:
+; SWITCH-NEXT:    br label [[BAR1_EXIT]]
+; SWITCH:       branch_6.i:
+; SWITCH-NEXT:    br label [[BAR1_EXIT]]
+; SWITCH:       default_branch.i:
+; SWITCH-NEXT:    br label [[BAR1_EXIT]]
+; SWITCH:       bar1.exit:
+; SWITCH-NEXT:    [[TMP2:%.*]] = phi i64 [ 5, [[BRANCH_0_I]] ], [ 9, [[BRANCH_2_I]] ], [ 2, [[BRANCH_4_I]] ], [ 7, [[BRANCH_6_I]] ], [ 3, [[DEFAULT_BRANCH_I]] ]
+; SWITCH-NEXT:    ret i64 [[TMP2]]
+;
+; CHECK-LABEL: define i64 @foo1(
+; CHECK-SAME: i64 [[A:%.*]]) {
+; CHECK-NEXT:    [[B:%.*]] = call i64 @bar1(i64 [[A]])
+; CHECK-NEXT:    ret i64 [[B]]
+;
+  %b = call i64 @bar1(i64 %a)
+  ret i64 %b
+}
+
+define i64 @foo2(i64 %a) {
+; LOOKUPTABLE-LABEL: define i64 @foo2(
+; LOOKUPTABLE-SAME: i64 [[TMP0:%.*]]) {
+; LOOKUPTABLE-NEXT:    switch i64 [[TMP0]], label [[UNREACHABLEDEFAULT_I:%.*]] [
+; LOOKUPTABLE-NEXT:      i64 0, label [[BRANCH_0_I:%.*]]
+; LOOKUPTABLE-NEXT:      i64 2, label [[BRANCH_2_I:%.*]]
+; LOOKUPTABLE-NEXT:      i64 4, label [[BRANCH_4_I:%.*]]
+; LOOKUPTABLE-NEXT:      i64 6, label [[BRANCH_6_I:%.*]]
+; LOOKUPTABLE-NEXT:    ]
+; LOOKUPTABLE:       branch_0.i:
+; LOOKUPTABLE-NEXT:    br label [[BAR2_EXIT:%.*]]
+; LOOKUPTABLE:       branch_2.i:
+; LOOKUPTABLE-NEXT:    br label [[BAR2_EXIT]]
+; LOOKUPTABLE:       branch_4.i:
+; LOOKUPTABLE-NEXT:    br label [[BAR2_EXIT]]
+; LOOKUPTABLE:       branch_6.i:
+; LOOKUPTABLE-NEXT:    br label [[BAR2_EXIT]]
+; LOOKUPTABLE:       unreachabledefault.i:
+; LOOKUPTABLE-NEXT:    unreachable
+; LOOKUPTABLE:       bar2.exit:
+; LOOKUPTABLE-NEXT:    [[TMP2:%.*]] = phi i64 [ 5, [[BRANCH_0_I]] ], [ 9, [[BRANCH_2_I]] ], [ 2, [[BRANCH_4_I]] ], [ 7, [[BRANCH_6_I]] ]
+; LOOKUPTABLE-NEXT:    ret i64 [[TMP2]]
+;
+; SWITCH-LABEL: define i64 @foo2(
+; SWITCH-SAME: i64 [[TMP0:%.*]]) {
+; SWITCH-NEXT:    switch i64 [[TMP0]], label [[UNREACHABLEDEFAULT_I:%.*]] [
+; SWITCH-NEXT:      i64 0, label [[BRANCH_0_I:%.*]]
+; SWITCH-NEXT:      i64 2, label [[BRANCH_2_I:%.*]]
+; SWITCH-NEXT:      i64 4, label [[BRANCH_4_I:%.*]]
+; SWITCH-NEXT:      i64 6, label [[BRANCH_6_I:%.*]]
+; SWITCH-NEXT:    ]
+; SWITCH:       branch_0.i:
+; SWITCH-NEXT:    br label [[BAR2_EXIT:%.*]]
+; SWITCH:       branch_2.i:
+; SWITCH-NEXT:    br label [[BAR2_EXIT]]
+; SWITCH:       branch_4.i:
+; SWITCH-NEXT:    br label [[BAR2_EXIT]]
+; SWITCH:       branch_6.i:
+; SWITCH-NEXT:    br label [[BAR2_EXIT]]
+; SWITCH:       unreachabledefault.i:
+; SWITCH-NEXT:    unreachable
+; SWITCH:       bar2.exit:
+; SWITCH-NEXT:    [[TMP2:%.*]] = phi i64 [ 5, [[BRANCH_0_I]] ], [ 9, [[BRANCH_2_I]] ], [ 2, [[BRANCH_4_I]] ], [ 7, [[BRANCH_6_I]] ]
+; SWITCH-NEXT:    ret i64 [[TMP2]]
+;
+; CHECK-LABEL: define i64 @foo2(
+; CHECK-SAME: i64 [[A:%.*]]) {
+; CHECK-NEXT:    switch i64 [[A]], label [[UNREACHABLEDEFAULT_I:%.*]] [
+; CHECK-NEXT:      i64 0, label [[BRANCH_0_I:%.*]]
+; CHECK-NEXT:      i64 2, label [[BRANCH_2_I:%.*]]
+; CHECK-NEXT:      i64 4, label [[BRANCH_4_I:%.*]]
+; CHECK-NEXT:      i64 6, label [[BRANCH_6_I:%.*]]
+; CHECK-NEXT:    ]
+; CHECK:       branch_0.i:
+; CHECK-NEXT:    br label [[BAR2_EXIT:%.*]]
+; CHECK:       branch_2.i:
+; CHECK-NEXT:    br label [[BAR2_EXIT]]
+; CHECK:       branch_4.i:
+; CHECK-NEXT:    br label [[BAR2_EXIT]]
+; CHECK:       branch_6.i:
+; CHECK-NEXT:    br label [[BAR2_EXIT]]
+; CHECK:       unreachabledefault.i:
+; CHECK-NEXT:    unreachable
+; CHECK:       bar2.exit:
+; CHECK-NEXT:    [[B_I:%.*]] = phi i64 [ 5, [[BRANCH_0_I]] ], [ 9, [[BRANCH_2_I]] ], [ 2, [[BRANCH_4_I]] ], [ 7, [[BRANCH_6_I]] ]
+; CHECK-NEXT:    ret i64 [[B_I]]
+;
+  %b = call i64 @bar2(i64 %a)
+  ret i64 %b
+}
+
+define i64 @bar1(i64 %a) {
+; LOOKUPTABLE-LABEL: define i64 @bar1(
+; LOOKUPTABLE-SAME: i64 [[TMP0:%.*]]) {
+; LOOKUPTABLE-NEXT:    switch i64 [[TMP0]], label [[DEFAULT_BRANCH:%.*]] [
+; LOOKUPTABLE-NEXT:      i64 0, label [[BRANCH_0:%.*]]
+; LOOKUPTABLE-NEXT:      i64 2, label [[BRANCH_2:%.*]]
+; LOOKUPTABLE-NEXT:      i64 4, label [[BRANCH_4:%.*]]
+; LOOKUPTABLE-NEXT:      i64 6, label [[BRANCH_6:%.*]]
+; LOOKUPTABLE-NEXT:    ]
+; LOOKUPTABLE:       branch_0:
+; LOOKUPTABLE-NEXT:    br label [[EXIT:%.*]]
+; LOOKUPTABLE:       branch_2:
+; LOOKUPTABLE-NEXT:    br label [[EXIT]]
+; LOOKUPTABLE:       branch_4:
+; LOOKUPTABLE-NEXT:    br label [[EXIT]]
+; LOOKUPTABLE:       branch_6:
+; LOOKUPTABLE-NEXT:    br label [[EXIT]]
+; LOOKUPTABLE:       default_branch:
+; LOOKUPTABLE-NEXT:    br label [[EXIT]]
+; LOOKUPTABLE:       exit:
+; LOOKUPTABLE-NEXT:    [[TMP2:%.*]] = phi i64 [ 5, [[BRANCH_0]] ], [ 9, [[BRANCH_2]] ], [ 2, [[BRANCH_4]] ], [ 7, [[BRANCH_6]] ], [ 3, [[DEFAULT_BRANCH]] ]
+; LOOKUPTABLE-NEXT:    ret i64 [[TMP2]]
+;
+; SWITCH-LABEL: define i64 @bar1(
+; SWITCH-SAME: i64 [[TMP0:%.*]]) {
+; SWITCH-NEXT:    switch i64 [[TMP0]], label [[DEFAULT_BRANCH:%.*]] [
+; SWITCH-NEXT:      i64 0, label [[BRANCH_0:%.*]]
+; SWITCH-NEXT:      i64 2, label [[BRANCH_2:%.*]]
+; SWITCH-NEXT:      i64 4, label [[BRANCH_4:%.*]]
+; SWITCH-NEXT:      i64 6, label [[BRANCH_6:%.*]]
+; SWITCH-NEXT:    ]
+; SWITCH:       branch_0:
+; SWITCH-NEXT:    br label [[EXIT:%.*]]
+; SWITCH:       branch_2:
+; SWITCH-NEXT:    br label [[EXIT]]
+; SWITCH:       branch_4:
+; SWITCH-NEXT:    br label [[EXIT]]
+; SWITCH:       branch_6:
+; SWITCH-NEXT:    br label [[EXIT]]
+; SWITCH:       default_branch:
+; SWITCH-NEXT:    br label [[EXIT]]
+; SWITCH:       exit:
+; SWITCH-NEXT:    [[TMP2:%.*]] = phi i64 [ 5, [[BRANCH_0]] ], [ 9, [[BRANCH_2]] ], [ 2, [[BRANCH_4]] ], [ 7, [[BRANCH_6]] ], [ 3, [[DEFAULT_BRANCH]] ]
+; SWITCH-NEXT:    ret i64 [[TMP2]]
+;
+; CHECK-LABEL: define i64 @bar1(
+; CHECK-SAME: i64 [[A:%.*]]) {
+; CHECK-NEXT:    switch i64 [[A]], label [[DEFAULT_BRANCH:%.*]] [
+; CHECK-NEXT:      i64 0, label [[BRANCH_0:%.*]]
+; CHECK-NEXT:      i64 2, label [[BRANCH_2:%.*]]
+; CHECK-NEXT:      i64 4, label [[BRANCH_4:%.*]]
+; CHECK-NEXT:      i64 6, label [[BRANCH_6:%.*]]
+; CHECK-NEXT:    ]
+; CHECK:       branch_0:
+; CHECK-NEXT:    br label [[EXIT:%.*]]
+; CHECK:       branch_2:
+; CHECK-NEXT:    br label [[EXIT]]
+; CHECK:       branch_4:
+; CHECK-NEXT:    br label [[EXIT]]
+; CHECK:       branch_6:
+; CHECK-NEXT:    br label [[EXIT]]
+; CHECK:       default_branch:
+; CHECK-NEXT:    br label [[EXIT]]
+; CHECK:       exit:
+; CHECK-NEXT:    [[B:%.*]] = phi i64 [ 5, [[BRANCH_0]] ], [ 9, [[BRANCH_2]] ], [ 2, [[BRANCH_4]] ], [ 7, [[BRANCH_6]] ], [ 3, [[DEFAULT_BRANCH]] ]
+; CHECK-NEXT:    ret i64 [[B]]
+;
+  switch i64 %a, label %default_branch [
+  i64 0, label %branch_0
+  i64 2, label %branch_2
+  i64 4, label %branch_4
+  i64 6, label %branch_6
+  ]
+
+branch_0:
+  br label %exit
+
+branch_2:
+  br label %exit
+
+branch_4:
+  br label %exit
+
+branch_6:
+  br label %exit
+
+default_branch:
+  br label %exit
+
+exit:
+  %b = phi i64 [ 5, %branch_0 ], [ 9, %branch_2 ], [ 2, %branch_4 ], [ 7, %branch_6 ], [ 3, %default_branch ]
+  ret i64 %b
+}
+
+define i64 @bar2(i64 %a) {
+; LOOKUPTABLE-LABEL: define i64 @bar2(
+; LOOKUPTABLE-SAME: i64 [[TMP0:%.*]]) {
+; LOOKUPTABLE-NEXT:    switch i64 [[TMP0]], label [[UNREACHABLEDEFAULT:%.*]] [
+; LOOKUPTABLE-NEXT:      i64 0, label [[BRANCH_0:%.*]]
+; LOOKUPTABLE-NEXT:      i64 2, label [[BRANCH_2:%.*]]
+; LOOKUPTABLE-NEXT:      i64 4, label [[BRANCH_4:%.*]]
+; LOOKUPTABLE-NEXT:      i64 6, label [[BRANCH_6:%.*]]
+; LOOKUPTABLE-NEXT:    ]
+; LOOKUPTABLE:       branch_0:
+; LOOKUPTABLE-NEXT:    br label [[EXIT:%.*]]
+; LOOKUPTABLE:       branch_2:
+; LOOKUPTABLE-NEXT:    br label [[EXIT]]
+; LOOKUPTABLE:       branch_4:
+; LOOKUPTABLE-NEXT:    br label [[EXIT]]
+; LOOKUPTABLE:       branch_6:
+; LOOKUPTABLE-NEXT:    br label [[EXIT]]
+; LOOKUPTABLE:       unreachabledefault:
+; LOOKUPTABLE-NEXT:    unreachable
+; LOOKUPTABLE:       exit:
+; LOOKUPTABLE-NEXT:    [[TMP2:%.*]] = phi i64 [ 5, [[BRANCH_0]] ], [ 9, [[BRANCH_2]] ], [ 2, [[BRANCH_4]] ], [ 7, [[BRANCH_6]] ]
+; LOOKUPTABLE-NEXT:    ret i64 [[TMP2]]
+;
+; SWITCH-LABEL: define i64 @bar2(
+; SWITCH-SAME: i64 [[TMP0:%.*]]) {
+; SWITCH-NEXT:    switch i64 [[TMP0]], label [[UNREACHABLEDEFAULT:%.*]] [
+; SWITCH-NEXT:      i64 0, label [[BRANCH_0:%.*]]
+; SWITCH-NEXT:      i64 2, label [[BRANCH_2:%.*]]
+; SWITCH-NEXT:      i64 4, label [[BRANCH_4:%.*]]
+; SWITCH-NEXT:      i64 6, label [[BRANCH_6:%.*]]
+; SWITCH-NEXT:    ]
+; SWITCH:       branch_0:
+; SWITCH-NEXT:    br label [[EXIT:%.*]]
+; SWITCH:       branch_2:
+; SWITCH-NEXT:    br label [[EXIT]]
+; SWITCH:       branch_4:
+; SWITCH-NEXT:    br label [[EXIT]]
+; SWITCH:       branch_6:
+; SWITCH-NEXT:    br label [[EXIT]]
+; SWITCH:       unreachabledefault:
+; SWITCH-NEXT:    unreachable
+; SWITCH:       exit:
+; SWITCH-NEXT:    [[TMP2:%.*]] = phi i64 [ 5, [[BRANCH_0]] ], [ 9, [[BRANCH_2]] ], [ 2, [[BRANCH_4]] ], [ 7, [[BRANCH_6]] ]
+; SWITCH-NEXT:    ret i64 [[TMP2]]
+;
+; CHECK-LABEL: define i64 @bar2(
+; CHECK-SAME: i64 [[A:%.*]]) {
+; CHECK-NEXT:    switch i64 [[A]], label [[UNREACHABLEDEFAULT:%.*]] [
+; CHECK-NEXT:      i64 0, label [[BRANCH_0:%.*]]
+; CHECK-NEXT:      i64 2, label [[BRANCH_2:%.*]]
+; CHECK-NEXT:      i64 4, label [[BRANCH_4:%.*]]
+; CHECK-NEXT:      i64 6, label [[BRANCH_6:%.*]]
+; CHECK-NEXT:    ]
+; CHECK:       branch_0:
+; CHECK-NEXT:    br label [[EXIT:%.*]]
+; CHECK:       branch_2:
+; CHECK-NEXT:    br label [[EXIT]]
+; CHECK:       branch_4:
+; CHECK-NEXT:    br label [[EXIT]]
+; CHECK:       branch_6:
+; CHECK-NEXT:    br label [[EXIT]]
+; CHECK:       unreachabledefault:
+; CHECK-NEXT:    unreachable
+; CHECK:       exit:
+; CHECK-NEXT:    [[B:%.*]] = phi i64 [ 5, [[BRANCH_0]] ], [ 9, [[BRANCH_2]] ], [ 2, [[BRANCH_4]] ], [ 7, [[BRANCH_6]] ]
+; CHECK-NEXT:    ret i64 [[B]]
+;
+  switch i64 %a, label %unreachabledefault [
+  i64 0, label %branch_0
+  i64 2, label %branch_2
+  i64 4, label %branch_4
+  i64 6, label %branch_6
+  ]
+
+branch_0:
+  br label %exit
+
+branch_2:
+  br label %exit
+
+branch_4:
+  br label %exit
+
+branch_6:
+  br label %exit
+
+unreachabledefault:
+  unreachable
+
+exit:
+  %b = phi i64 [ 5, %branch_0 ], [ 9, %branch_2 ], [ 2, %branch_4 ], [ 7, %branch_6 ]
+  ret i64 %b
+}

diff  --git a/llvm/test/Transforms/Inline/inline-switch-default.ll b/llvm/test/Transforms/Inline/inline-switch-default.ll
new file mode 100644
index 00000000000000..44f1304e82dff0
--- /dev/null
+++ b/llvm/test/Transforms/Inline/inline-switch-default.ll
@@ -0,0 +1,216 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 4
+; RUN: opt %s -S -passes=inline -inline-threshold=26 -min-jump-table-entries=4 | FileCheck %s -check-prefix=LOOKUPTABLE
+; RUN: opt %s -S -passes=inline -inline-threshold=21 -min-jump-table-entries=5 | FileCheck %s -check-prefix=SWITCH
+
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+; The `bar1` should not be inlined since there is a default branch.
+
+define i64 @foo1(i64 %a) {
+; LOOKUPTABLE-LABEL: define i64 @foo1(
+; LOOKUPTABLE-SAME: i64 [[A:%.*]]) {
+; LOOKUPTABLE-NEXT:    [[B:%.*]] = call i64 @bar1(i64 [[A]])
+; LOOKUPTABLE-NEXT:    ret i64 [[B]]
+;
+; SWITCH-LABEL: define i64 @foo1(
+; SWITCH-SAME: i64 [[A:%.*]]) {
+; SWITCH-NEXT:    [[B:%.*]] = call i64 @bar1(i64 [[A]])
+; SWITCH-NEXT:    ret i64 [[B]]
+;
+  %b = call i64 @bar1(i64 %a)
+  ret i64 %b
+}
+
+define i64 @foo2(i64 %a) {
+; LOOKUPTABLE-LABEL: define i64 @foo2(
+; LOOKUPTABLE-SAME: i64 [[A:%.*]]) {
+; LOOKUPTABLE-NEXT:    switch i64 [[A]], label [[UNREACHABLEDEFAULT_I:%.*]] [
+; LOOKUPTABLE-NEXT:      i64 0, label [[BRANCH_0_I:%.*]]
+; LOOKUPTABLE-NEXT:      i64 2, label [[BRANCH_2_I:%.*]]
+; LOOKUPTABLE-NEXT:      i64 4, label [[BRANCH_4_I:%.*]]
+; LOOKUPTABLE-NEXT:      i64 6, label [[BRANCH_6_I:%.*]]
+; LOOKUPTABLE-NEXT:    ]
+; LOOKUPTABLE:       branch_0.i:
+; LOOKUPTABLE-NEXT:    br label [[BAR2_EXIT:%.*]]
+; LOOKUPTABLE:       branch_2.i:
+; LOOKUPTABLE-NEXT:    br label [[BAR2_EXIT]]
+; LOOKUPTABLE:       branch_4.i:
+; LOOKUPTABLE-NEXT:    br label [[BAR2_EXIT]]
+; LOOKUPTABLE:       branch_6.i:
+; LOOKUPTABLE-NEXT:    br label [[BAR2_EXIT]]
+; LOOKUPTABLE:       unreachabledefault.i:
+; LOOKUPTABLE-NEXT:    unreachable
+; LOOKUPTABLE:       bar2.exit:
+; LOOKUPTABLE-NEXT:    [[B_I:%.*]] = phi i64 [ 5, [[BRANCH_0_I]] ], [ 9, [[BRANCH_2_I]] ], [ 2, [[BRANCH_4_I]] ], [ 7, [[BRANCH_6_I]] ]
+; LOOKUPTABLE-NEXT:    ret i64 [[B_I]]
+;
+; SWITCH-LABEL: define i64 @foo2(
+; SWITCH-SAME: i64 [[A:%.*]]) {
+; SWITCH-NEXT:    switch i64 [[A]], label [[UNREACHABLEDEFAULT_I:%.*]] [
+; SWITCH-NEXT:      i64 0, label [[BRANCH_0_I:%.*]]
+; SWITCH-NEXT:      i64 2, label [[BRANCH_2_I:%.*]]
+; SWITCH-NEXT:      i64 4, label [[BRANCH_4_I:%.*]]
+; SWITCH-NEXT:      i64 6, label [[BRANCH_6_I:%.*]]
+; SWITCH-NEXT:    ]
+; SWITCH:       branch_0.i:
+; SWITCH-NEXT:    br label [[BAR2_EXIT:%.*]]
+; SWITCH:       branch_2.i:
+; SWITCH-NEXT:    br label [[BAR2_EXIT]]
+; SWITCH:       branch_4.i:
+; SWITCH-NEXT:    br label [[BAR2_EXIT]]
+; SWITCH:       branch_6.i:
+; SWITCH-NEXT:    br label [[BAR2_EXIT]]
+; SWITCH:       unreachabledefault.i:
+; SWITCH-NEXT:    unreachable
+; SWITCH:       bar2.exit:
+; SWITCH-NEXT:    [[B_I:%.*]] = phi i64 [ 5, [[BRANCH_0_I]] ], [ 9, [[BRANCH_2_I]] ], [ 2, [[BRANCH_4_I]] ], [ 7, [[BRANCH_6_I]] ]
+; SWITCH-NEXT:    ret i64 [[B_I]]
+;
+  %b = call i64 @bar2(i64 %a)
+  ret i64 %b
+}
+
+define i64 @bar1(i64 %a) {
+; LOOKUPTABLE-LABEL: define i64 @bar1(
+; LOOKUPTABLE-SAME: i64 [[A:%.*]]) {
+; LOOKUPTABLE-NEXT:    switch i64 [[A]], label [[DEFAULT_BRANCH:%.*]] [
+; LOOKUPTABLE-NEXT:      i64 0, label [[BRANCH_0:%.*]]
+; LOOKUPTABLE-NEXT:      i64 2, label [[BRANCH_2:%.*]]
+; LOOKUPTABLE-NEXT:      i64 4, label [[BRANCH_4:%.*]]
+; LOOKUPTABLE-NEXT:      i64 6, label [[BRANCH_6:%.*]]
+; LOOKUPTABLE-NEXT:    ]
+; LOOKUPTABLE:       branch_0:
+; LOOKUPTABLE-NEXT:    br label [[EXIT:%.*]]
+; LOOKUPTABLE:       branch_2:
+; LOOKUPTABLE-NEXT:    br label [[EXIT]]
+; LOOKUPTABLE:       branch_4:
+; LOOKUPTABLE-NEXT:    br label [[EXIT]]
+; LOOKUPTABLE:       branch_6:
+; LOOKUPTABLE-NEXT:    br label [[EXIT]]
+; LOOKUPTABLE:       default_branch:
+; LOOKUPTABLE-NEXT:    br label [[EXIT]]
+; LOOKUPTABLE:       exit:
+; LOOKUPTABLE-NEXT:    [[B:%.*]] = phi i64 [ 5, [[BRANCH_0]] ], [ 9, [[BRANCH_2]] ], [ 2, [[BRANCH_4]] ], [ 7, [[BRANCH_6]] ], [ 3, [[DEFAULT_BRANCH]] ]
+; LOOKUPTABLE-NEXT:    ret i64 [[B]]
+;
+; SWITCH-LABEL: define i64 @bar1(
+; SWITCH-SAME: i64 [[A:%.*]]) {
+; SWITCH-NEXT:    switch i64 [[A]], label [[DEFAULT_BRANCH:%.*]] [
+; SWITCH-NEXT:      i64 0, label [[BRANCH_0:%.*]]
+; SWITCH-NEXT:      i64 2, label [[BRANCH_2:%.*]]
+; SWITCH-NEXT:      i64 4, label [[BRANCH_4:%.*]]
+; SWITCH-NEXT:      i64 6, label [[BRANCH_6:%.*]]
+; SWITCH-NEXT:    ]
+; SWITCH:       branch_0:
+; SWITCH-NEXT:    br label [[EXIT:%.*]]
+; SWITCH:       branch_2:
+; SWITCH-NEXT:    br label [[EXIT]]
+; SWITCH:       branch_4:
+; SWITCH-NEXT:    br label [[EXIT]]
+; SWITCH:       branch_6:
+; SWITCH-NEXT:    br label [[EXIT]]
+; SWITCH:       default_branch:
+; SWITCH-NEXT:    br label [[EXIT]]
+; SWITCH:       exit:
+; SWITCH-NEXT:    [[B:%.*]] = phi i64 [ 5, [[BRANCH_0]] ], [ 9, [[BRANCH_2]] ], [ 2, [[BRANCH_4]] ], [ 7, [[BRANCH_6]] ], [ 3, [[DEFAULT_BRANCH]] ]
+; SWITCH-NEXT:    ret i64 [[B]]
+;
+  switch i64 %a, label %default_branch [
+  i64 0, label %branch_0
+  i64 2, label %branch_2
+  i64 4, label %branch_4
+  i64 6, label %branch_6
+  ]
+
+branch_0:
+  br label %exit
+
+branch_2:
+  br label %exit
+
+branch_4:
+  br label %exit
+
+branch_6:
+  br label %exit
+
+default_branch:
+  br label %exit
+
+exit:
+  %b = phi i64 [ 5, %branch_0 ], [ 9, %branch_2 ], [ 2, %branch_4 ], [ 7, %branch_6 ], [ 3, %default_branch ]
+  ret i64 %b
+}
+
+define i64 @bar2(i64 %a) {
+; LOOKUPTABLE-LABEL: define i64 @bar2(
+; LOOKUPTABLE-SAME: i64 [[A:%.*]]) {
+; LOOKUPTABLE-NEXT:    switch i64 [[A]], label [[UNREACHABLEDEFAULT:%.*]] [
+; LOOKUPTABLE-NEXT:      i64 0, label [[BRANCH_0:%.*]]
+; LOOKUPTABLE-NEXT:      i64 2, label [[BRANCH_2:%.*]]
+; LOOKUPTABLE-NEXT:      i64 4, label [[BRANCH_4:%.*]]
+; LOOKUPTABLE-NEXT:      i64 6, label [[BRANCH_6:%.*]]
+; LOOKUPTABLE-NEXT:    ]
+; LOOKUPTABLE:       branch_0:
+; LOOKUPTABLE-NEXT:    br label [[EXIT:%.*]]
+; LOOKUPTABLE:       branch_2:
+; LOOKUPTABLE-NEXT:    br label [[EXIT]]
+; LOOKUPTABLE:       branch_4:
+; LOOKUPTABLE-NEXT:    br label [[EXIT]]
+; LOOKUPTABLE:       branch_6:
+; LOOKUPTABLE-NEXT:    br label [[EXIT]]
+; LOOKUPTABLE:       unreachabledefault:
+; LOOKUPTABLE-NEXT:    unreachable
+; LOOKUPTABLE:       exit:
+; LOOKUPTABLE-NEXT:    [[B:%.*]] = phi i64 [ 5, [[BRANCH_0]] ], [ 9, [[BRANCH_2]] ], [ 2, [[BRANCH_4]] ], [ 7, [[BRANCH_6]] ]
+; LOOKUPTABLE-NEXT:    ret i64 [[B]]
+;
+; SWITCH-LABEL: define i64 @bar2(
+; SWITCH-SAME: i64 [[A:%.*]]) {
+; SWITCH-NEXT:    switch i64 [[A]], label [[UNREACHABLEDEFAULT:%.*]] [
+; SWITCH-NEXT:      i64 0, label [[BRANCH_0:%.*]]
+; SWITCH-NEXT:      i64 2, label [[BRANCH_2:%.*]]
+; SWITCH-NEXT:      i64 4, label [[BRANCH_4:%.*]]
+; SWITCH-NEXT:      i64 6, label [[BRANCH_6:%.*]]
+; SWITCH-NEXT:    ]
+; SWITCH:       branch_0:
+; SWITCH-NEXT:    br label [[EXIT:%.*]]
+; SWITCH:       branch_2:
+; SWITCH-NEXT:    br label [[EXIT]]
+; SWITCH:       branch_4:
+; SWITCH-NEXT:    br label [[EXIT]]
+; SWITCH:       branch_6:
+; SWITCH-NEXT:    br label [[EXIT]]
+; SWITCH:       unreachabledefault:
+; SWITCH-NEXT:    unreachable
+; SWITCH:       exit:
+; SWITCH-NEXT:    [[B:%.*]] = phi i64 [ 5, [[BRANCH_0]] ], [ 9, [[BRANCH_2]] ], [ 2, [[BRANCH_4]] ], [ 7, [[BRANCH_6]] ]
+; SWITCH-NEXT:    ret i64 [[B]]
+;
+  switch i64 %a, label %unreachabledefault [
+  i64 0, label %branch_0
+  i64 2, label %branch_2
+  i64 4, label %branch_4
+  i64 6, label %branch_6
+  ]
+
+branch_0:
+  br label %exit
+
+branch_2:
+  br label %exit
+
+branch_4:
+  br label %exit
+
+branch_6:
+  br label %exit
+
+unreachabledefault:
+  unreachable
+
+exit:
+  %b = phi i64 [ 5, %branch_0 ], [ 9, %branch_2 ], [ 2, %branch_4 ], [ 7, %branch_6 ]
+  ret i64 %b
+}


        


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