[llvm] [DFAJumpThreading] Enable DFAJumpThread by default. (PR #157646)

via llvm-commits llvm-commits at lists.llvm.org
Tue Sep 9 04:05:19 PDT 2025 

https://github.com/buggfg created https://github.com/llvm/llvm-project/pull/157646

We recommend setting `dfa-jump-thread` to be enabled by default. It’s a mature optimization that’s been supported since GCC 9.1.0. At the `-O2` opt level, both the GCC and ICX compilers have this optimization enabled by default. 

Once it’s enabled, we saw a **13% performance improvement** in the CoreMark benchmark on the X86 platform (Intel i9-11900K Rocket Lake), and even a **15% increase** on the KunMingHu FPGA. Additionally, we verified the correctness of this pass using SPEC 2017.

>From fa5628b7b543e04c30f1fc244fb4ec01fca33964 Mon Sep 17 00:00:00 2001
From: buggfg <3171290993 at qq.com>
Date: Tue, 9 Sep 2025 19:03:16 +0800
Subject: [PATCH] Enable DFAJumpThread by default.

Co-Authored-By: YinZd <104915588+nothiny at users.noreply.github.com>
Co-Authored-By: ict-ql <168183727+ict-ql at users.noreply.github.com>
Co-Authored-By: Lin Wang <wanglulin at ict.ac.cn>
---
 llvm/lib/Passes/PassBuilderPipelines.cpp                      | 2 +-
 llvm/test/Other/new-pm-defaults.ll                            | 1 +
 llvm/test/Other/new-pm-thinlto-postlink-defaults.ll           | 1 +
 llvm/test/Other/new-pm-thinlto-postlink-pgo-defaults.ll       | 1 +
 llvm/test/Other/new-pm-thinlto-postlink-samplepgo-defaults.ll | 1 +
 llvm/test/Other/new-pm-thinlto-prelink-defaults.ll            | 1 +
 llvm/test/Other/new-pm-thinlto-prelink-pgo-defaults.ll        | 1 +
 llvm/test/Other/new-pm-thinlto-prelink-samplepgo-defaults.ll  | 1 +
 8 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/llvm/lib/Passes/PassBuilderPipelines.cpp b/llvm/lib/Passes/PassBuilderPipelines.cpp
index 98821bb1408a7..c6460121bc763 100644
--- a/llvm/lib/Passes/PassBuilderPipelines.cpp
+++ b/llvm/lib/Passes/PassBuilderPipelines.cpp
@@ -224,7 +224,7 @@ static cl::opt<bool> EnableLoopHeaderDuplication(
 static cl::opt<bool>
     EnableDFAJumpThreading("enable-dfa-jump-thread",
                            cl::desc("Enable DFA jump threading"),
-                           cl::init(false), cl::Hidden);
+                           cl::init(true), cl::Hidden);
 
 static cl::opt<bool>
     EnableHotColdSplit("hot-cold-split",
diff --git a/llvm/test/Other/new-pm-defaults.ll b/llvm/test/Other/new-pm-defaults.ll
index c554fdbf4c799..fb62ea0354a6b 100644
--- a/llvm/test/Other/new-pm-defaults.ll
+++ b/llvm/test/Other/new-pm-defaults.ll
@@ -209,6 +209,7 @@
 ; CHECK-O-NEXT: Running analysis: DemandedBitsAnalysis
 ; CHECK-O-NEXT: Running pass: InstCombinePass
 ; CHECK-EP-PEEPHOLE-NEXT: Running pass: NoOpFunctionPass
+; CHECK-O23SZ-NEXT: Running pass: DFAJumpThreadingPass
 ; CHECK-O23SZ-NEXT: Running pass: JumpThreadingPass
 ; CHECK-O23SZ-NEXT: Running analysis: LazyValueAnalysis
 ; CHECK-O23SZ-NEXT: Running pass: CorrelatedValuePropagationPass
diff --git a/llvm/test/Other/new-pm-thinlto-postlink-defaults.ll b/llvm/test/Other/new-pm-thinlto-postlink-defaults.ll
index 62bb02d9b3c40..2ac033620b2f2 100644
--- a/llvm/test/Other/new-pm-thinlto-postlink-defaults.ll
+++ b/llvm/test/Other/new-pm-thinlto-postlink-defaults.ll
@@ -134,6 +134,7 @@
 ; CHECK-O-NEXT: Running pass: BDCEPass
 ; CHECK-O-NEXT: Running analysis: DemandedBitsAnalysis
 ; CHECK-O-NEXT: Running pass: InstCombinePass
+; CHECK-O23SZ-NEXT: Running pass: DFAJumpThreadingPass
 ; CHECK-O23SZ-NEXT: Running pass: JumpThreadingPass
 ; CHECK-O23SZ-NEXT: Running analysis: LazyValueAnalysis
 ; CHECK-O23SZ-NEXT: Running pass: CorrelatedValuePropagationPass
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 0da7a9f73bdce..8a5d1c0737a96 100644
--- a/llvm/test/Other/new-pm-thinlto-postlink-pgo-defaults.ll
+++ b/llvm/test/Other/new-pm-thinlto-postlink-pgo-defaults.ll
@@ -119,6 +119,7 @@
 ; CHECK-O-NEXT: Running pass: BDCEPass
 ; CHECK-O-NEXT: Running analysis: DemandedBitsAnalysis
 ; CHECK-O-NEXT: Running pass: InstCombinePass
+; CHECK-O23SZ-NEXT: Running pass: DFAJumpThreadingPass
 ; CHECK-O23SZ-NEXT: Running pass: JumpThreadingPass
 ; CHECK-O23SZ-NEXT: Running analysis: LazyValueAnalysis
 ; CHECK-O23SZ-NEXT: Running pass: CorrelatedValuePropagationPass
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 38b7890682783..1c6658a11d89f 100644
--- a/llvm/test/Other/new-pm-thinlto-postlink-samplepgo-defaults.ll
+++ b/llvm/test/Other/new-pm-thinlto-postlink-samplepgo-defaults.ll
@@ -128,6 +128,7 @@
 ; CHECK-O-NEXT: Running pass: BDCEPass
 ; CHECK-O-NEXT: Running analysis: DemandedBitsAnalysis
 ; CHECK-O-NEXT: Running pass: InstCombinePass
+; CHECK-O23SZ-NEXT: Running pass: DFAJumpThreadingPass
 ; CHECK-O23SZ-NEXT: Running pass: JumpThreadingPass
 ; CHECK-O23SZ-NEXT: Running analysis: LazyValueAnalysis
 ; CHECK-O23SZ-NEXT: Running pass: CorrelatedValuePropagationPass
diff --git a/llvm/test/Other/new-pm-thinlto-prelink-defaults.ll b/llvm/test/Other/new-pm-thinlto-prelink-defaults.ll
index 5aacd26def2be..5a03dabd8d7d1 100644
--- a/llvm/test/Other/new-pm-thinlto-prelink-defaults.ll
+++ b/llvm/test/Other/new-pm-thinlto-prelink-defaults.ll
@@ -166,6 +166,7 @@
 ; CHECK-O-NEXT: Running pass: BDCEPass
 ; CHECK-O-NEXT: Running analysis: DemandedBitsAnalysis
 ; CHECK-O-NEXT: Running pass: InstCombinePass
+; CHECK-O23SZ-NEXT: Running pass: DFAJumpThreadingPass
 ; CHECK-O23SZ-NEXT: Running pass: JumpThreadingPass
 ; CHECK-O23SZ-NEXT: Running analysis: LazyValueAnalysis
 ; CHECK-O23SZ-NEXT: Running pass: CorrelatedValuePropagationPass
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 f6a9406596803..76fcf28c87d2d 100644
--- a/llvm/test/Other/new-pm-thinlto-prelink-pgo-defaults.ll
+++ b/llvm/test/Other/new-pm-thinlto-prelink-pgo-defaults.ll
@@ -168,6 +168,7 @@
 ; CHECK-O-NEXT: Running pass: BDCEPass
 ; CHECK-O-NEXT: Running analysis: DemandedBitsAnalysis
 ; CHECK-O-NEXT: Running pass: InstCombinePass
+; CHECK-O23SZ-NEXT: Running pass: DFAJumpThreadingPass
 ; CHECK-O23SZ-NEXT: Running pass: JumpThreadingPass
 ; CHECK-O23SZ-NEXT: Running analysis: LazyValueAnalysis
 ; CHECK-O23SZ-NEXT: Running pass: CorrelatedValuePropagationPass
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 48a9433d24999..06d4d42ef8f36 100644
--- a/llvm/test/Other/new-pm-thinlto-prelink-samplepgo-defaults.ll
+++ b/llvm/test/Other/new-pm-thinlto-prelink-samplepgo-defaults.ll
@@ -132,6 +132,7 @@
 ; CHECK-O-NEXT: Running pass: BDCEPass
 ; CHECK-O-NEXT: Running analysis: DemandedBitsAnalysis
 ; CHECK-O-NEXT: Running pass: InstCombinePass
+; CHECK-O23SZ-NEXT: Running pass: DFAJumpThreadingPass
 ; CHECK-O23SZ-NEXT: Running pass: JumpThreadingPass
 ; CHECK-O23SZ-NEXT: Running analysis: LazyValueAnalysis
 ; CHECK-O23SZ-NEXT: Running pass: CorrelatedValuePropagationPass

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