[llvm] [Transform] Clean up strlen loop idiom (PR #132421)
Henry Jiang via llvm-commits
llvm-commits at lists.llvm.org
Fri Mar 21 10:54:25 PDT 2025
https://github.com/mustartt updated https://github.com/llvm/llvm-project/pull/132421
>From b212a292b810254e984efe5dfa2d638b4600874e Mon Sep 17 00:00:00 2001
From: Henry Jiang <henry.jiang1 at ibm.com>
Date: Fri, 21 Mar 2025 12:54:50 -0400
Subject: [PATCH 1/2] bail out before modifing cfg
---
.../Transforms/Scalar/LoopIdiomRecognize.cpp | 39 +++++++------------
1 file changed, 15 insertions(+), 24 deletions(-)
diff --git a/llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp b/llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp
index b91cdc0748581..7f92f5f65a972 100644
--- a/llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp
@@ -1515,16 +1515,6 @@ bool LoopIdiomRecognize::runOnNoncountableLoop() {
recognizeShiftUntilLessThan() || recognizeAndInsertStrLen();
}
-/// Check if a Value is either a nullptr or a constant int zero
-static bool isZeroConstant(const Value *Val) {
- if (isa<ConstantPointerNull>(Val))
- return true;
- const ConstantInt *CmpZero = dyn_cast<ConstantInt>(Val);
- if (!CmpZero || !CmpZero->isZero())
- return false;
- return true;
-}
-
/// Check if the given conditional branch is based on the comparison between
/// a variable and zero, and if the variable is non-zero or zero (JmpOnZero is
/// true), the control yields to the loop entry. If the branch matches the
@@ -1540,7 +1530,8 @@ static Value *matchCondition(BranchInst *BI, BasicBlock *LoopEntry,
if (!Cond)
return nullptr;
- if (!isZeroConstant(Cond->getOperand(1)))
+ const ConstantInt *CmpZero = dyn_cast<ConstantInt>(Cond->getOperand(1));
+ if (!CmpZero || !CmpZero->isZero())
return nullptr;
BasicBlock *TrueSucc = BI->getSuccessor(0);
@@ -1656,11 +1647,7 @@ class StrlenVerifier {
if (!Ev)
return false;
- LLVM_DEBUG({
- dbgs() << "loop exit phi scev: ";
- Ev->print(dbgs());
- dbgs() << "\n";
- });
+ LLVM_DEBUG(dbgs() << "loop exit phi scev: " << *Ev << "\n");
// Since we verified that the loop trip count will be a valid strlen
// idiom, we can expand all lcssa phi with {n,+,1} as (n + strlen) and use
@@ -1763,6 +1750,18 @@ bool LoopIdiomRecognize::recognizeAndInsertStrLen() {
BasicBlock *Preheader = CurLoop->getLoopPreheader();
BasicBlock *LoopExitBB = CurLoop->getExitBlock();
+ if (Verifier.OpWidth == 8) {
+ if (DisableLIRP::Strlen)
+ return false;
+ if (!isLibFuncEmittable(Preheader->getModule(), TLI, LibFunc_strlen))
+ return false;
+ } else {
+ if (DisableLIRP::Wcslen)
+ return false;
+ if (!isLibFuncEmittable(Preheader->getModule(), TLI, LibFunc_wcslen))
+ return false;
+ }
+
IRBuilder<> Builder(Preheader->getTerminator());
SCEVExpander Expander(*SE, Preheader->getModule()->getDataLayout(),
"strlen_idiom");
@@ -1772,16 +1771,8 @@ bool LoopIdiomRecognize::recognizeAndInsertStrLen() {
Value *StrLenFunc = nullptr;
if (Verifier.OpWidth == 8) {
- if (DisableLIRP::Strlen)
- return false;
- if (!isLibFuncEmittable(Preheader->getModule(), TLI, LibFunc_strlen))
- return false;
StrLenFunc = emitStrLen(MaterialzedBase, Builder, *DL, TLI);
} else {
- if (DisableLIRP::Wcslen)
- return false;
- if (!isLibFuncEmittable(Preheader->getModule(), TLI, LibFunc_wcslen))
- return false;
StrLenFunc = emitWcsLen(MaterialzedBase, Builder, *DL, TLI);
}
assert(StrLenFunc && "Failed to emit strlen function.");
>From b1f81d054f76af609d3fc4544688ea2d686b0bcd Mon Sep 17 00:00:00 2001
From: Henry Jiang <henry.jiang1 at ibm.com>
Date: Fri, 21 Mar 2025 12:55:02 -0400
Subject: [PATCH 2/2] remove verify pass
---
llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp | 6 +-----
llvm/test/Transforms/LoopIdiom/strlen-not-emittable.ll | 2 +-
llvm/test/Transforms/LoopIdiom/strlen.ll | 2 +-
llvm/test/Transforms/LoopIdiom/wcslen16.ll | 2 +-
llvm/test/Transforms/LoopIdiom/wcslen32.ll | 2 +-
5 files changed, 5 insertions(+), 9 deletions(-)
diff --git a/llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp b/llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp
index 7f92f5f65a972..d754e6b09bbe5 100644
--- a/llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp
@@ -1602,11 +1602,7 @@ class StrlenVerifier {
return false;
LoadBaseEv = LoadEv->getStart();
- LLVM_DEBUG({
- dbgs() << "pointer load scev: ";
- LoadEv->print(outs());
- dbgs() << "\n";
- });
+ LLVM_DEBUG(dbgs() << "pointer load scev: " << *LoadEv << "\n");
const SCEVConstant *Step =
dyn_cast<SCEVConstant>(LoadEv->getStepRecurrence(*SE));
diff --git a/llvm/test/Transforms/LoopIdiom/strlen-not-emittable.ll b/llvm/test/Transforms/LoopIdiom/strlen-not-emittable.ll
index 0be76cbd42a72..00fbe89846a30 100644
--- a/llvm/test/Transforms/LoopIdiom/strlen-not-emittable.ll
+++ b/llvm/test/Transforms/LoopIdiom/strlen-not-emittable.ll
@@ -1,4 +1,4 @@
-; RUN: opt -passes='loop(loop-idiom),verify' < %s -S | FileCheck %s
+; RUN: opt -passes='loop(loop-idiom)' < %s -S | FileCheck %s
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"
diff --git a/llvm/test/Transforms/LoopIdiom/strlen.ll b/llvm/test/Transforms/LoopIdiom/strlen.ll
index 137a17f541cd4..c1141177c659f 100644
--- a/llvm/test/Transforms/LoopIdiom/strlen.ll
+++ b/llvm/test/Transforms/LoopIdiom/strlen.ll
@@ -1,5 +1,5 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
-; RUN: opt -passes='loop(loop-idiom),verify' < %s -S | FileCheck %s
+; RUN: opt -passes='loop(loop-idiom)' < %s -S | FileCheck %s
declare void @other()
declare void @use(ptr)
diff --git a/llvm/test/Transforms/LoopIdiom/wcslen16.ll b/llvm/test/Transforms/LoopIdiom/wcslen16.ll
index d3b0b8d208cd8..8be51869f1f2e 100644
--- a/llvm/test/Transforms/LoopIdiom/wcslen16.ll
+++ b/llvm/test/Transforms/LoopIdiom/wcslen16.ll
@@ -1,5 +1,5 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
-; RUN: opt -passes='loop(loop-idiom),verify' < %s -S | FileCheck %s
+; RUN: opt -passes='loop(loop-idiom)' < %s -S | FileCheck %s
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"
diff --git a/llvm/test/Transforms/LoopIdiom/wcslen32.ll b/llvm/test/Transforms/LoopIdiom/wcslen32.ll
index 488afff86c245..2c7ceb4d187e6 100644
--- a/llvm/test/Transforms/LoopIdiom/wcslen32.ll
+++ b/llvm/test/Transforms/LoopIdiom/wcslen32.ll
@@ -1,5 +1,5 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
-; RUN: opt -passes='loop(loop-idiom),verify' < %s -S | FileCheck %s
+; RUN: opt -passes='loop(loop-idiom)' < %s -S | FileCheck %s
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"
More information about the llvm-commits
mailing list