[RISCV][EVL] Drop EVLIndVarSimplifyPass from the pipeline #151483
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@llvm/pr-subscribers-backend-risc-v Author: Shih-Po Hung (arcbbb) ChangesWith the VPlan-based canonical induction variable replacement landed in #147222, it appears to cover the functionality previously provided by the EVLIndVarSimplify pass introduced in #131005. As a next step, this patch proposes disabling EVLIndVarSimplify by default to begin a gradual phase-out. Full diff: https://github.com/llvm/llvm-project/pull/151483.diff 1 Files Affected:
diff --git a/llvm/lib/Target/RISCV/RISCVTargetMachine.cpp b/llvm/lib/Target/RISCV/RISCVTargetMachine.cpp
index da6ac2f6f31e9..9d648237743b4 100644
--- a/llvm/lib/Target/RISCV/RISCVTargetMachine.cpp
+++ b/llvm/lib/Target/RISCV/RISCVTargetMachine.cpp
@@ -114,6 +114,11 @@ static cl::opt<bool>
cl::desc("Enable Machine Pipeliner for RISC-V"),
cl::init(false), cl::Hidden);
+static cl::opt<bool> EnableEVLIndVarSimplify(
+ "riscv-simplify-evl-iv",
+ cl::desc("Enable the EVLIndVarSimplify pass."), cl::init(false),
+ cl::Hidden);
+
extern "C" LLVM_ABI LLVM_EXTERNAL_VISIBILITY void LLVMInitializeRISCVTarget() {
RegisterTargetMachine<RISCVTargetMachine> X(getTheRISCV32Target());
RegisterTargetMachine<RISCVTargetMachine> Y(getTheRISCV64Target());
@@ -645,7 +650,7 @@ void RISCVTargetMachine::registerPassBuilderCallbacks(PassBuilder &PB) {
PB.registerVectorizerEndEPCallback(
[](FunctionPassManager &FPM, OptimizationLevel Level) {
- if (Level.isOptimizingForSpeed())
+ if (Level.isOptimizingForSpeed() && EnableEVLIndVarSimplify)
FPM.addPass(createFunctionToLoopPassAdaptor(EVLIndVarSimplifyPass()));
});
}
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✅ With the latest revision this PR passed the C/C++ code formatter. |
lukel97
reviewed
Jul 31, 2025
There was a problem hiding this comment.
I think we're quite early in the LLVM release cycle, should we just go ahead and stop emitting the metadata from the LoopVectorizer and remove the pass?
I don't think EVLIndVarSimplfiyPass is actually kicking in today anymore, it always seems to bail with Cannot retrieve IV from loop vector.body becausecannot recognize induction variable after #147222. So I'm not sure if adding a flag really changes anything.
mshockwave
reviewed
Jul 31, 2025
I'm ok with that too |
arcbbb
changed the title
Let's handle the metadata in a separate PR and keep this one focused on removing the pass from the pipeline. @mshockwave I do have a question regarding the metadata. Does "stop emitting" imply a complete removal, or just adding a switch to disable it? I'm not sure it is consistent to remove the metadata entirely while there's still a pass that queries it. |
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LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/123/builds/24704 Here is the relevant piece of the build log for the reference |
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LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/137/builds/22971 Here is the relevant piece of the build log for the reference |
Sorry this message slipped through my radar: yes, I think we could just add a switch to disable it for now. |
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With the VPlan-based canonical induction variable replacement landed in #147222, it appears to cover the functionality previously provided by the EVLIndVarSimplify pass introduced in #131005.
This patch suggests removing EVLIndVarSimplify from the RISC-V pipeline as a follow-up step. Feedback is very welcome!