[llvm] Reenable JumpTableToSwitch pass by default (PR #83229)

Tue Feb 27 22:53:40 PST 2024

llvmbot wrote:




@llvm/pr-subscribers-llvm-transforms

Author: Alexander Shaposhnikov (alexander-shaposhnikov)

<details>
<summary>Changes</summary>

This is a recommit of 1069823ce7 (https://github.com/llvm/llvm-project/pull/82546)
with the default value of JumpTableSizeThreshold decreased from 10 to 5.
Added a comment with data points in JumpTableToSwitch.cpp.

Test plan: 
1. ninja check-all
2. Built LLVM (with LLVM_ENABLE_PROJECTS="bolt;mlir;compiler-rt;flang;llvm;clang;lld;clang-tools-extra") with the bootstrapped version of Clang.

---
Full diff: https://github.com/llvm/llvm-project/pull/83229.diff


9 Files Affected:

- (modified) llvm/lib/Passes/PassBuilderPipelines.cpp (+1-1) 
- (modified) llvm/lib/Transforms/Scalar/JumpTableToSwitch.cpp (+9-1) 
- (modified) llvm/test/Other/new-pm-defaults.ll (+1-5) 
- (modified) llvm/test/Other/new-pm-thinlto-postlink-defaults.ll (+1) 
- (modified) llvm/test/Other/new-pm-thinlto-postlink-pgo-defaults.ll (+1) 
- (modified) llvm/test/Other/new-pm-thinlto-postlink-samplepgo-defaults.ll (+1) 
- (modified) llvm/test/Other/new-pm-thinlto-prelink-defaults.ll (+1) 
- (modified) llvm/test/Other/new-pm-thinlto-prelink-pgo-defaults.ll (+1) 
- (modified) llvm/test/Other/new-pm-thinlto-prelink-samplepgo-defaults.ll (+1) 


``````````diff

diff --git a/llvm/lib/Passes/PassBuilderPipelines.cpp b/llvm/lib/Passes/PassBuilderPipelines.cpp
index 142bd50b3798e0..17b55b63ac03cf 100644
--- a/llvm/lib/Passes/PassBuilderPipelines.cpp
+++ b/llvm/lib/Passes/PassBuilderPipelines.cpp
@@ -247,7 +247,7 @@ static cl::opt<bool>
 
 static cl::opt<bool> EnableJumpTableToSwitch(
     "enable-jump-table-to-switch",
-    cl::desc("Enable JumpTableToSwitch pass (default = off)"));
+    cl::desc("Enable JumpTableToSwitch pass (default = on)"), cl::init(true));
 
 // This option is used in simplifying testing SampleFDO optimizations for
 // profile loading.
diff --git a/llvm/lib/Transforms/Scalar/JumpTableToSwitch.cpp b/llvm/lib/Transforms/Scalar/JumpTableToSwitch.cpp
index f9712dbbf68a6a..5ff7836f98ab6c 100644
--- a/llvm/lib/Transforms/Scalar/JumpTableToSwitch.cpp
+++ b/llvm/lib/Transforms/Scalar/JumpTableToSwitch.cpp
@@ -18,11 +18,19 @@
 
 using namespace llvm;
 
+// The choice of this threshold is motivated by the following data points:
+// 1. Chromium successfully builds with JumpTableSizeThreshold=10, and this
+// build includes many third-party C++ projects.
+// 2. Flang experiences several compilation slow-down issues with
+// JumpTableSizeThreshold=9, builds successfully with JumpTableSizeThreshold=8.
+// On several investigated pathological examples the expansion of jump tables
+// introduced more than 100K new callsites where inlining happened.
+// 3. TODO: Consider increasing this value.
 static cl::opt<unsigned>
     JumpTableSizeThreshold("jump-table-to-switch-size-threshold", cl::Hidden,
                            cl::desc("Only split jump tables with size less or "
                                     "equal than JumpTableSizeThreshold."),
-                           cl::init(10));
+                           cl::init(5));
 
 // TODO: Consider adding a cost model for profitability analysis of this
 // transformation. Currently we replace a jump table with a switch if all the
diff --git a/llvm/test/Other/new-pm-defaults.ll b/llvm/test/Other/new-pm-defaults.ll
index 51fb93daa4dfa6..285077ff8e31a9 100644
--- a/llvm/test/Other/new-pm-defaults.ll
+++ b/llvm/test/Other/new-pm-defaults.ll
@@ -71,10 +71,6 @@
 ; RUN:     -passes='default<O3>' -S  %s 2>&1 \
 ; RUN:     | FileCheck %s --check-prefixes=CHECK-O,CHECK-DEFAULT,CHECK-O3,%llvmcheckext,CHECK-EP-OPTIMIZER-LAST,CHECK-O23SZ
 
-; RUN: opt -disable-verify -verify-analysis-invalidation=0 -eagerly-invalidate-analyses=0 -debug-pass-manager \
-; RUN:     -passes='default<O3>' -enable-jump-table-to-switch -S  %s 2>&1 \
-; RUN:     | FileCheck %s --check-prefixes=CHECK-O,CHECK-DEFAULT,CHECK-O3,CHECK-JUMP-TABLE-TO-SWITCH,CHECK-O23SZ,%llvmcheckext
-
 ; RUN: opt -disable-verify -verify-analysis-invalidation=0 -eagerly-invalidate-analyses=0 -debug-pass-manager \
 ; RUN:     -passes='default<O3>' -enable-matrix -S  %s 2>&1 \
 ; RUN:     | FileCheck %s --check-prefixes=CHECK-O,CHECK-DEFAULT,CHECK-O3,CHECK-O23SZ,%llvmcheckext,CHECK-MATRIX
@@ -155,7 +151,7 @@
 ; CHECK-O23SZ-NEXT: Running analysis: LazyValueAnalysis
 ; CHECK-O23SZ-NEXT: Running pass: CorrelatedValuePropagationPass
 ; CHECK-O23SZ-NEXT: Invalidating analysis: LazyValueAnalysis
-; CHECK-JUMP-TABLE-TO-SWITCH-NEXT: Running pass: JumpTableToSwitchPass
+; CHECK-O23SZ-NEXT: Running pass: JumpTableToSwitchPass
 ; CHECK-O-NEXT: Running pass: SimplifyCFGPass
 ; CHECK-O-NEXT: Running pass: InstCombinePass
 ; CHECK-O23SZ-NEXT: Running pass: AggressiveInstCombinePass
diff --git a/llvm/test/Other/new-pm-thinlto-postlink-defaults.ll b/llvm/test/Other/new-pm-thinlto-postlink-defaults.ll
index 064362eabbf839..29a4d79037427e 100644
--- a/llvm/test/Other/new-pm-thinlto-postlink-defaults.ll
+++ b/llvm/test/Other/new-pm-thinlto-postlink-defaults.ll
@@ -90,6 +90,7 @@
 ; CHECK-O23SZ-NEXT: Running analysis: LazyValueAnalysis
 ; CHECK-O23SZ-NEXT: Running pass: CorrelatedValuePropagationPass
 ; CHECK-O23SZ-NEXT: Invalidating analysis: LazyValueAnalysis
+; CHECK-O23SZ-NEXT: Running pass: JumpTableToSwitchPass
 ; CHECK-O-NEXT: Running pass: SimplifyCFGPass
 ; CHECK-O-NEXT: Running pass: InstCombinePass
 ; CHECK-O23SZ-NEXT: Running pass: AggressiveInstCombinePass
diff --git a/llvm/test/Other/new-pm-thinlto-postlink-pgo-defaults.ll b/llvm/test/Other/new-pm-thinlto-postlink-pgo-defaults.ll
index 19a44867e434ac..bf06782c86f862 100644
--- a/llvm/test/Other/new-pm-thinlto-postlink-pgo-defaults.ll
+++ b/llvm/test/Other/new-pm-thinlto-postlink-pgo-defaults.ll
@@ -78,6 +78,7 @@
 ; CHECK-O23SZ-NEXT: Running analysis: LazyValueAnalysis
 ; CHECK-O23SZ-NEXT: Running pass: CorrelatedValuePropagationPass
 ; CHECK-O23SZ-NEXT: Invalidating analysis: LazyValueAnalysis
+; CHECK-O23SZ-NEXT: Running pass: JumpTableToSwitchPass
 ; CHECK-O-NEXT: Running pass: SimplifyCFGPass
 ; CHECK-O-NEXT: Running pass: InstCombinePass
 ; CHECK-O23SZ-NEXT: Running pass: AggressiveInstCombinePass
diff --git a/llvm/test/Other/new-pm-thinlto-postlink-samplepgo-defaults.ll b/llvm/test/Other/new-pm-thinlto-postlink-samplepgo-defaults.ll
index ac80a31d8fd4bc..0cc61121de01ce 100644
--- a/llvm/test/Other/new-pm-thinlto-postlink-samplepgo-defaults.ll
+++ b/llvm/test/Other/new-pm-thinlto-postlink-samplepgo-defaults.ll
@@ -86,6 +86,7 @@
 ; CHECK-O23SZ-NEXT: Running analysis: LazyValueAnalysis
 ; CHECK-O23SZ-NEXT: Running pass: CorrelatedValuePropagationPass
 ; CHECK-O23SZ-NEXT: Invalidating analysis: LazyValueAnalysis
+; CHECK-O23SZ-NEXT: Running pass: JumpTableToSwitchPass
 ; CHECK-O-NEXT: Running pass: SimplifyCFGPass
 ; CHECK-O-NEXT: Running pass: InstCombinePass
 ; CHECK-O23SZ-NEXT: Running pass: AggressiveInstCombinePass
diff --git a/llvm/test/Other/new-pm-thinlto-prelink-defaults.ll b/llvm/test/Other/new-pm-thinlto-prelink-defaults.ll
index 6486639e07b49c..0e5839797afe9e 100644
--- a/llvm/test/Other/new-pm-thinlto-prelink-defaults.ll
+++ b/llvm/test/Other/new-pm-thinlto-prelink-defaults.ll
@@ -121,6 +121,7 @@
 ; CHECK-O23SZ-NEXT: Running analysis: LazyValueAnalysis
 ; CHECK-O23SZ-NEXT: Running pass: CorrelatedValuePropagationPass
 ; CHECK-O23SZ-NEXT: Invalidating analysis: LazyValueAnalysis
+; CHECK-O23SZ-NEXT: Running pass: JumpTableToSwitchPass
 ; CHECK-O-NEXT: Running pass: SimplifyCFGPass
 ; CHECK-O-NEXT: Running pass: InstCombinePass
 ; CHECK-O23SZ-NEXT: Running pass: AggressiveInstCombinePass
diff --git a/llvm/test/Other/new-pm-thinlto-prelink-pgo-defaults.ll b/llvm/test/Other/new-pm-thinlto-prelink-pgo-defaults.ll
index 09f9f0f48baddb..68c2e581463000 100644
--- a/llvm/test/Other/new-pm-thinlto-prelink-pgo-defaults.ll
+++ b/llvm/test/Other/new-pm-thinlto-prelink-pgo-defaults.ll
@@ -118,6 +118,7 @@
 ; CHECK-O23SZ-NEXT: Running analysis: LazyValueAnalysis
 ; CHECK-O23SZ-NEXT: Running pass: CorrelatedValuePropagationPass
 ; CHECK-O23SZ-NEXT: Invalidating analysis: LazyValueAnalysis
+; CHECK-O23SZ-NEXT: Running pass: JumpTableToSwitchPass
 ; CHECK-O-NEXT: Running pass: SimplifyCFGPass
 ; CHECK-O-NEXT: Running pass: InstCombinePass
 ; CHECK-O-NEXT: Running analysis: BlockFrequencyAnalysis on foo
diff --git a/llvm/test/Other/new-pm-thinlto-prelink-samplepgo-defaults.ll b/llvm/test/Other/new-pm-thinlto-prelink-samplepgo-defaults.ll
index 47bdbfd2d357d4..8311a009711d1e 100644
--- a/llvm/test/Other/new-pm-thinlto-prelink-samplepgo-defaults.ll
+++ b/llvm/test/Other/new-pm-thinlto-prelink-samplepgo-defaults.ll
@@ -90,6 +90,7 @@
 ; CHECK-O23SZ-NEXT: Running analysis: LazyValueAnalysis
 ; CHECK-O23SZ-NEXT: Running pass: CorrelatedValuePropagationPass
 ; CHECK-O23SZ-NEXT: Invalidating analysis: LazyValueAnalysis
+; CHECK-O23SZ-NEXT: Running pass: JumpTableToSwitchPass
 ; CHECK-O-NEXT: Running pass: SimplifyCFGPass
 ; CHECK-O-NEXT: Running pass: InstCombinePass
 ; CHECK-O23SZ-NEXT: Running pass: AggressiveInstCombinePass

``````````

</details>


https://github.com/llvm/llvm-project/pull/83229
