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

buggfg · Nothiny · ict-ql · web-flow · commit 0ba7bfc34fa2 · 2025-11-04T13:25:49.000+08:00
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.

Co-authored-by: YinZd &lt;104915588+nothiny@users.noreply.github.com&gt;
Co-authored-by: ict-ql &lt;168183727+ict-ql@users.noreply.github.com&gt;
Co-authored-by: Lin Wang &lt;wanglulin@ict.ac.cn&gt;
diff --git a/llvm/lib/Passes/PassBuilderPipelines.cpp b/llvm/lib/Passes/PassBuilderPipelines.cpp
@@ -228,7 +228,7 @@ 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
@@ -208,6 +208,7 @@
 ; 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
@@ -133,6 +133,7 @@
 ; 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
@@ -118,6 +118,7 @@
 ; 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
@@ -127,6 +127,7 @@
 ; 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
@@ -165,6 +165,7 @@
 ; 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
@@ -167,6 +167,7 @@
 ; 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
@@ -131,6 +131,7 @@
 ; 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
