[llvm] [LoopPeel] Support min/max intrinsics in loop peeling (PR #93162)

Sergey Kachkov via llvm-commits llvm-commits at lists.llvm.org
Thu May 23 02:52:24 PDT 2024


https://github.com/skachkov-sc created https://github.com/llvm/llvm-project/pull/93162

Motivating example: https://godbolt.org/z/qfxz8rKac

This example shows very different loop peeling behaviour for similar code depending on whether icmp+select was canonicalized to min/max intrinsic or not.

This patch adds processing of min/max intrinsics in LoopPeel in the similar way as it was done for conditional statements: for min/max(IterVal, BoundVal) we peel iterations where IterVal < BoundVal for monotonically increasing IterVal; for monotonically decreasing IterVal we peel iterations where IterVal > BoundVal (strict comparision predicates are used to minimize number of peeled iterations).

Compile-time results on llvm test-suite (including SPEC benchmarks) shows 3 tests affected by this:
```
Program                                                                         loop-peel.NumPeeled                             
                                                                                baseline            loop-peel-min-max      diff 
test-suite :: MultiSource/Benchmarks/mediabench/mpeg2/mpeg2dec/mpeg2decode.test   0.00                2.00                  inf%
                   test-suite :: MultiSource/Applications/JM/lencod/lencod.test   7.00                9.00                 28.6%
              test-suite :: External/SPEC/CINT2006/464.h264ref/464.h264ref.test   6.00                7.00                 16.7%
```


>From 5aa404b4dd8827822ef4b310323eb0a4487b5b60 Mon Sep 17 00:00:00 2001
From: Sergey Kachkov <sergey.kachkov at syntacore.com>
Date: Thu, 16 May 2024 18:28:04 +0300
Subject: [PATCH 1/2] [LoopPeel] Add pre-commit test for min/max intrinsics

---
 .../peel-loop-min-max-intrinsics.ll           | 189 ++++++++++++++++++
 1 file changed, 189 insertions(+)
 create mode 100644 llvm/test/Transforms/LoopUnroll/peel-loop-min-max-intrinsics.ll

diff --git a/llvm/test/Transforms/LoopUnroll/peel-loop-min-max-intrinsics.ll b/llvm/test/Transforms/LoopUnroll/peel-loop-min-max-intrinsics.ll
new file mode 100644
index 0000000000000..bf895d6de3850
--- /dev/null
+++ b/llvm/test/Transforms/LoopUnroll/peel-loop-min-max-intrinsics.ll
@@ -0,0 +1,189 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 4
+; RUN: opt < %s -S -passes=loop-unroll -unroll-peel-max-count=2 | FileCheck %s
+
+declare void @foo(i32)
+
+declare i32 @llvm.smin.i32(i32, i32)
+declare i32 @llvm.smax.i32(i32, i32)
+declare i32 @llvm.umin.i32(i32, i32)
+declare i32 @llvm.umax.i32(i32, i32)
+
+define void @test1(i32 %N) {
+; CHECK-LABEL: define void @test1(
+; CHECK-SAME: i32 [[N:%.*]]) {
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[CMP5_NOT:%.*]] = icmp eq i32 [[N]], 0
+; CHECK-NEXT:    br i1 [[CMP5_NOT]], label [[FOR_COND_CLEANUP:%.*]], label [[FOR_BODY_PREHEADER:%.*]]
+; CHECK:       for.body.preheader:
+; CHECK-NEXT:    br label [[FOR_BODY:%.*]]
+; CHECK:       for.body:
+; CHECK-NEXT:    [[I_06:%.*]] = phi i32 [ [[INC:%.*]], [[FOR_BODY]] ], [ 0, [[FOR_BODY_PREHEADER]] ]
+; CHECK-NEXT:    [[COND:%.*]] = tail call i32 @llvm.umin.i32(i32 [[I_06]], i32 2)
+; CHECK-NEXT:    tail call void @foo(i32 [[COND]])
+; CHECK-NEXT:    [[INC]] = add nuw i32 [[I_06]], 1
+; CHECK-NEXT:    [[EXITCOND_NOT:%.*]] = icmp eq i32 [[INC]], [[N]]
+; CHECK-NEXT:    br i1 [[EXITCOND_NOT]], label [[FOR_COND_CLEANUP_LOOPEXIT:%.*]], label [[FOR_BODY]]
+; CHECK:       for.cond.cleanup.loopexit:
+; CHECK-NEXT:    br label [[FOR_COND_CLEANUP]]
+; CHECK:       for.cond.cleanup:
+; CHECK-NEXT:    ret void
+;
+entry:
+  %cmp5.not = icmp eq i32 %N, 0
+  br i1 %cmp5.not, label %for.cond.cleanup, label %for.body
+
+for.body:
+  %i.06 = phi i32 [ %inc, %for.body ], [ 0, %entry ]
+  %cond = tail call i32 @llvm.umin.i32(i32 %i.06, i32 2)
+  tail call void @foo(i32 %cond)
+  %inc = add nuw i32 %i.06, 1
+  %exitcond.not = icmp eq i32 %inc, %N
+  br i1 %exitcond.not, label %for.cond.cleanup, label %for.body
+
+for.cond.cleanup:
+  ret void
+}
+
+define void @test2(i32 %N) {
+; CHECK-LABEL: define void @test2(
+; CHECK-SAME: i32 [[N:%.*]]) {
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[CMP5_NOT:%.*]] = icmp eq i32 [[N]], 0
+; CHECK-NEXT:    br i1 [[CMP5_NOT]], label [[FOR_COND_CLEANUP:%.*]], label [[FOR_BODY_PREHEADER:%.*]]
+; CHECK:       for.body.preheader:
+; CHECK-NEXT:    br label [[FOR_BODY:%.*]]
+; CHECK:       for.body:
+; CHECK-NEXT:    [[I_06:%.*]] = phi i32 [ [[INC:%.*]], [[FOR_BODY]] ], [ 0, [[FOR_BODY_PREHEADER]] ]
+; CHECK-NEXT:    [[COND:%.*]] = tail call i32 @llvm.umax.i32(i32 [[I_06]], i32 2)
+; CHECK-NEXT:    tail call void @foo(i32 [[COND]])
+; CHECK-NEXT:    [[INC]] = add nuw i32 [[I_06]], 1
+; CHECK-NEXT:    [[EXITCOND_NOT:%.*]] = icmp eq i32 [[INC]], [[N]]
+; CHECK-NEXT:    br i1 [[EXITCOND_NOT]], label [[FOR_COND_CLEANUP_LOOPEXIT:%.*]], label [[FOR_BODY]]
+; CHECK:       for.cond.cleanup.loopexit:
+; CHECK-NEXT:    br label [[FOR_COND_CLEANUP]]
+; CHECK:       for.cond.cleanup:
+; CHECK-NEXT:    ret void
+;
+entry:
+  %cmp5.not = icmp eq i32 %N, 0
+  br i1 %cmp5.not, label %for.cond.cleanup, label %for.body
+
+for.body:
+  %i.06 = phi i32 [ %inc, %for.body ], [ 0, %entry ]
+  %cond = tail call i32 @llvm.umax.i32(i32 %i.06, i32 2)
+  tail call void @foo(i32 %cond)
+  %inc = add nuw i32 %i.06, 1
+  %exitcond.not = icmp eq i32 %inc, %N
+  br i1 %exitcond.not, label %for.cond.cleanup, label %for.body
+
+for.cond.cleanup:
+  ret void
+}
+
+define void @test3(i32 %N) {
+; CHECK-LABEL: define void @test3(
+; CHECK-SAME: i32 [[N:%.*]]) {
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[CMP5:%.*]] = icmp slt i32 [[N]], 0
+; CHECK-NEXT:    br i1 [[CMP5]], label [[FOR_BODY_PREHEADER:%.*]], label [[FOR_COND_CLEANUP:%.*]]
+; CHECK:       for.body.preheader:
+; CHECK-NEXT:    br label [[FOR_BODY:%.*]]
+; CHECK:       for.body:
+; CHECK-NEXT:    [[I_06:%.*]] = phi i32 [ [[DEC:%.*]], [[FOR_BODY]] ], [ 0, [[FOR_BODY_PREHEADER]] ]
+; CHECK-NEXT:    [[COND:%.*]] = tail call i32 @llvm.smax.i32(i32 [[I_06]], i32 -2)
+; CHECK-NEXT:    tail call void @foo(i32 [[COND]])
+; CHECK-NEXT:    [[DEC]] = add nsw i32 [[I_06]], -1
+; CHECK-NEXT:    [[CMP:%.*]] = icmp sgt i32 [[DEC]], [[N]]
+; CHECK-NEXT:    br i1 [[CMP]], label [[FOR_BODY]], label [[FOR_COND_CLEANUP_LOOPEXIT:%.*]]
+; CHECK:       for.cond.cleanup.loopexit:
+; CHECK-NEXT:    br label [[FOR_COND_CLEANUP]]
+; CHECK:       for.cond.cleanup:
+; CHECK-NEXT:    ret void
+;
+entry:
+  %cmp5 = icmp slt i32 %N, 0
+  br i1 %cmp5, label %for.body, label %for.cond.cleanup
+
+for.body:
+  %i.06 = phi i32 [ %dec, %for.body ], [ 0, %entry ]
+  %cond = tail call i32 @llvm.smax.i32(i32 %i.06, i32 -2)
+  tail call void @foo(i32 %cond)
+  %dec = add nsw i32 %i.06, -1
+  %cmp = icmp sgt i32 %dec, %N
+  br i1 %cmp, label %for.body, label %for.cond.cleanup
+
+for.cond.cleanup:
+  ret void
+}
+
+define void @test4(i32 %N) {
+; CHECK-LABEL: define void @test4(
+; CHECK-SAME: i32 [[N:%.*]]) {
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[CMP5:%.*]] = icmp slt i32 [[N]], 0
+; CHECK-NEXT:    br i1 [[CMP5]], label [[FOR_BODY_PREHEADER:%.*]], label [[FOR_COND_CLEANUP:%.*]]
+; CHECK:       for.body.preheader:
+; CHECK-NEXT:    br label [[FOR_BODY:%.*]]
+; CHECK:       for.body:
+; CHECK-NEXT:    [[I_06:%.*]] = phi i32 [ [[DEC:%.*]], [[FOR_BODY]] ], [ 0, [[FOR_BODY_PREHEADER]] ]
+; CHECK-NEXT:    [[COND:%.*]] = tail call i32 @llvm.smin.i32(i32 [[I_06]], i32 -2)
+; CHECK-NEXT:    tail call void @foo(i32 noundef signext [[COND]])
+; CHECK-NEXT:    [[DEC]] = add nsw i32 [[I_06]], -1
+; CHECK-NEXT:    [[CMP:%.*]] = icmp sgt i32 [[DEC]], [[N]]
+; CHECK-NEXT:    br i1 [[CMP]], label [[FOR_BODY]], label [[FOR_COND_CLEANUP_LOOPEXIT:%.*]]
+; CHECK:       for.cond.cleanup.loopexit:
+; CHECK-NEXT:    br label [[FOR_COND_CLEANUP]]
+; CHECK:       for.cond.cleanup:
+; CHECK-NEXT:    ret void
+;
+entry:
+  %cmp5 = icmp slt i32 %N, 0
+  br i1 %cmp5, label %for.body, label %for.cond.cleanup
+
+for.body:
+  %i.06 = phi i32 [ %dec, %for.body ], [ 0, %entry ]
+  %cond = tail call i32 @llvm.smin.i32(i32 %i.06, i32 -2)
+  tail call void @foo(i32 noundef signext %cond)
+  %dec = add nsw i32 %i.06, -1
+  %cmp = icmp sgt i32 %dec, %N
+  br i1 %cmp, label %for.body, label %for.cond.cleanup
+
+for.cond.cleanup:
+  ret void
+}
+
+define void @test_negative(i32 %End, i32 %Step) {
+; CHECK-LABEL: define void @test_negative(
+; CHECK-SAME: i32 [[END:%.*]], i32 [[STEP:%.*]]) {
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[CMP_NOT5:%.*]] = icmp eq i32 [[END]], 0
+; CHECK-NEXT:    br i1 [[CMP_NOT5]], label [[FOR_COND_CLEANUP:%.*]], label [[FOR_BODY_PREHEADER:%.*]]
+; CHECK:       for.body.preheader:
+; CHECK-NEXT:    br label [[FOR_BODY:%.*]]
+; CHECK:       for.body:
+; CHECK-NEXT:    [[I_06:%.*]] = phi i32 [ [[ADD:%.*]], [[FOR_BODY]] ], [ 0, [[FOR_BODY_PREHEADER]] ]
+; CHECK-NEXT:    [[COND:%.*]] = tail call i32 @llvm.smin.i32(i32 [[I_06]], i32 2)
+; CHECK-NEXT:    tail call void @foo(i32 [[COND]])
+; CHECK-NEXT:    [[ADD]] = add nsw i32 [[I_06]], [[STEP]]
+; CHECK-NEXT:    [[CMP_NOT:%.*]] = icmp eq i32 [[ADD]], [[END]]
+; CHECK-NEXT:    br i1 [[CMP_NOT]], label [[FOR_COND_CLEANUP_LOOPEXIT:%.*]], label [[FOR_BODY]]
+; CHECK:       for.cond.cleanup.loopexit:
+; CHECK-NEXT:    br label [[FOR_COND_CLEANUP]]
+; CHECK:       for.cond.cleanup:
+; CHECK-NEXT:    ret void
+;
+entry:
+  %cmp.not5 = icmp eq i32 %End, 0
+  br i1 %cmp.not5, label %for.cond.cleanup, label %for.body
+
+for.body:
+  %i.06 = phi i32 [ %add, %for.body ], [ 0, %entry ]
+  %cond = tail call i32 @llvm.smin.i32(i32 %i.06, i32 2)
+  tail call void @foo(i32 %cond)
+  %add = add nsw i32 %i.06, %Step
+  %cmp.not = icmp eq i32 %add, %End
+  br i1 %cmp.not, label %for.cond.cleanup, label %for.body
+
+for.cond.cleanup:
+  ret void
+}

>From c5a8d648afd9d8d8b7b2ad3eaf8711505c6a729e Mon Sep 17 00:00:00 2001
From: Sergey Kachkov <sergey.kachkov at syntacore.com>
Date: Thu, 16 May 2024 18:34:52 +0300
Subject: [PATCH 2/2] [LoopPeel] Support min/max intrinsics in loop peeling

---
 llvm/lib/Transforms/Utils/LoopPeel.cpp        |  49 +++++++
 .../peel-loop-min-max-intrinsics.ll           | 131 +++++++++++++++---
 2 files changed, 164 insertions(+), 16 deletions(-)

diff --git a/llvm/lib/Transforms/Utils/LoopPeel.cpp b/llvm/lib/Transforms/Utils/LoopPeel.cpp
index f76fa3bb6c611..a6d37b9bdf11d 100644
--- a/llvm/lib/Transforms/Utils/LoopPeel.cpp
+++ b/llvm/lib/Transforms/Utils/LoopPeel.cpp
@@ -449,10 +449,59 @@ static unsigned countToEliminateCompares(Loop &L, unsigned MaxPeelCount,
     DesiredPeelCount = std::max(DesiredPeelCount, NewPeelCount);
   };
 
+  auto ComputePeelCountMinMax = [&](IntrinsicInst *II) {
+    bool IsSigned;
+    switch (II->getIntrinsicID()) {
+    case Intrinsic::smax:
+    case Intrinsic::smin:
+      IsSigned = true;
+      break;
+    case Intrinsic::umax:
+    case Intrinsic::umin:
+      IsSigned = false;
+      break;
+    default:
+      return;
+    }
+    Value *LHS = II->getOperand(0), *RHS = II->getOperand(1);
+    const SCEV *BoundSCEV, *IterSCEV;
+    if (L.isLoopInvariant(LHS)) {
+      BoundSCEV = SE.getSCEV(LHS);
+      IterSCEV = SE.getSCEV(RHS);
+    } else if (L.isLoopInvariant(RHS)) {
+      BoundSCEV = SE.getSCEV(RHS);
+      IterSCEV = SE.getSCEV(LHS);
+    } else
+      return;
+    const auto *AddRec = dyn_cast<SCEVAddRecExpr>(IterSCEV);
+    // For simplicity, we support only affine recurrences.
+    if (!AddRec || !AddRec->isAffine() || AddRec->getLoop() != &L)
+      return;
+    const SCEV *Step = AddRec->getStepRecurrence(SE);
+    // To minimize number of peeled iterations, we use strict relational
+    // predicates here.
+    ICmpInst::Predicate Pred;
+    if (SE.isKnownPositive(Step))
+      Pred = IsSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT;
+    else if (SE.isKnownNegative(Step))
+      Pred = IsSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
+    else
+      return;
+    const SCEV *IterVal = AddRec->evaluateAtIteration(
+        SE.getConstant(AddRec->getType(), DesiredPeelCount), SE);
+    while (DesiredPeelCount < MaxPeelCount &&
+           SE.isKnownPredicate(Pred, IterVal, BoundSCEV)) {
+      IterVal = SE.getAddExpr(IterVal, Step);
+      ++DesiredPeelCount;
+    }
+  };
+
   for (BasicBlock *BB : L.blocks()) {
     for (Instruction &I : *BB) {
       if (SelectInst *SI = dyn_cast<SelectInst>(&I))
         ComputePeelCount(SI->getCondition(), 0);
+      if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(&I))
+        ComputePeelCountMinMax(II);
     }
 
     auto *BI = dyn_cast<BranchInst>(BB->getTerminator());
diff --git a/llvm/test/Transforms/LoopUnroll/peel-loop-min-max-intrinsics.ll b/llvm/test/Transforms/LoopUnroll/peel-loop-min-max-intrinsics.ll
index bf895d6de3850..1a3f60b482793 100644
--- a/llvm/test/Transforms/LoopUnroll/peel-loop-min-max-intrinsics.ll
+++ b/llvm/test/Transforms/LoopUnroll/peel-loop-min-max-intrinsics.ll
@@ -15,14 +15,37 @@ define void @test1(i32 %N) {
 ; CHECK-NEXT:    [[CMP5_NOT:%.*]] = icmp eq i32 [[N]], 0
 ; CHECK-NEXT:    br i1 [[CMP5_NOT]], label [[FOR_COND_CLEANUP:%.*]], label [[FOR_BODY_PREHEADER:%.*]]
 ; CHECK:       for.body.preheader:
+; CHECK-NEXT:    br label [[FOR_BODY_PEEL_BEGIN:%.*]]
+; CHECK:       for.body.peel.begin:
+; CHECK-NEXT:    br label [[FOR_BODY_PEEL:%.*]]
+; CHECK:       for.body.peel:
+; CHECK-NEXT:    [[COND_PEEL:%.*]] = tail call i32 @llvm.umin.i32(i32 0, i32 2)
+; CHECK-NEXT:    tail call void @foo(i32 [[COND_PEEL]])
+; CHECK-NEXT:    [[INC_PEEL:%.*]] = add nuw i32 0, 1
+; CHECK-NEXT:    [[EXITCOND_NOT_PEEL:%.*]] = icmp eq i32 [[INC_PEEL]], [[N]]
+; CHECK-NEXT:    br i1 [[EXITCOND_NOT_PEEL]], label [[FOR_COND_CLEANUP_LOOPEXIT:%.*]], label [[FOR_BODY_PEEL_NEXT:%.*]]
+; CHECK:       for.body.peel.next:
+; CHECK-NEXT:    br label [[FOR_BODY_PEEL2:%.*]]
+; CHECK:       for.body.peel2:
+; CHECK-NEXT:    [[COND_PEEL3:%.*]] = tail call i32 @llvm.umin.i32(i32 [[INC_PEEL]], i32 2)
+; CHECK-NEXT:    tail call void @foo(i32 [[COND_PEEL3]])
+; CHECK-NEXT:    [[INC_PEEL4:%.*]] = add nuw i32 [[INC_PEEL]], 1
+; CHECK-NEXT:    [[EXITCOND_NOT_PEEL5:%.*]] = icmp eq i32 [[INC_PEEL4]], [[N]]
+; CHECK-NEXT:    br i1 [[EXITCOND_NOT_PEEL5]], label [[FOR_COND_CLEANUP_LOOPEXIT]], label [[FOR_BODY_PEEL_NEXT1:%.*]]
+; CHECK:       for.body.peel.next1:
+; CHECK-NEXT:    br label [[FOR_BODY_PEEL_NEXT6:%.*]]
+; CHECK:       for.body.peel.next6:
+; CHECK-NEXT:    br label [[FOR_BODY_PREHEADER_PEEL_NEWPH:%.*]]
+; CHECK:       for.body.preheader.peel.newph:
 ; CHECK-NEXT:    br label [[FOR_BODY:%.*]]
 ; CHECK:       for.body:
-; CHECK-NEXT:    [[I_06:%.*]] = phi i32 [ [[INC:%.*]], [[FOR_BODY]] ], [ 0, [[FOR_BODY_PREHEADER]] ]
-; CHECK-NEXT:    [[COND:%.*]] = tail call i32 @llvm.umin.i32(i32 [[I_06]], i32 2)
-; CHECK-NEXT:    tail call void @foo(i32 [[COND]])
+; CHECK-NEXT:    [[I_06:%.*]] = phi i32 [ [[INC:%.*]], [[FOR_BODY]] ], [ [[INC_PEEL4]], [[FOR_BODY_PREHEADER_PEEL_NEWPH]] ]
+; CHECK-NEXT:    tail call void @foo(i32 2)
 ; CHECK-NEXT:    [[INC]] = add nuw i32 [[I_06]], 1
 ; CHECK-NEXT:    [[EXITCOND_NOT:%.*]] = icmp eq i32 [[INC]], [[N]]
-; CHECK-NEXT:    br i1 [[EXITCOND_NOT]], label [[FOR_COND_CLEANUP_LOOPEXIT:%.*]], label [[FOR_BODY]]
+; CHECK-NEXT:    br i1 [[EXITCOND_NOT]], label [[FOR_COND_CLEANUP_LOOPEXIT_LOOPEXIT:%.*]], label [[FOR_BODY]], !llvm.loop [[LOOP0:![0-9]+]]
+; CHECK:       for.cond.cleanup.loopexit.loopexit:
+; CHECK-NEXT:    br label [[FOR_COND_CLEANUP_LOOPEXIT]]
 ; CHECK:       for.cond.cleanup.loopexit:
 ; CHECK-NEXT:    br label [[FOR_COND_CLEANUP]]
 ; CHECK:       for.cond.cleanup:
@@ -51,14 +74,37 @@ define void @test2(i32 %N) {
 ; CHECK-NEXT:    [[CMP5_NOT:%.*]] = icmp eq i32 [[N]], 0
 ; CHECK-NEXT:    br i1 [[CMP5_NOT]], label [[FOR_COND_CLEANUP:%.*]], label [[FOR_BODY_PREHEADER:%.*]]
 ; CHECK:       for.body.preheader:
+; CHECK-NEXT:    br label [[FOR_BODY_PEEL_BEGIN:%.*]]
+; CHECK:       for.body.peel.begin:
+; CHECK-NEXT:    br label [[FOR_BODY_PEEL:%.*]]
+; CHECK:       for.body.peel:
+; CHECK-NEXT:    [[COND_PEEL:%.*]] = tail call i32 @llvm.umax.i32(i32 0, i32 2)
+; CHECK-NEXT:    tail call void @foo(i32 [[COND_PEEL]])
+; CHECK-NEXT:    [[INC_PEEL:%.*]] = add nuw i32 0, 1
+; CHECK-NEXT:    [[EXITCOND_NOT_PEEL:%.*]] = icmp eq i32 [[INC_PEEL]], [[N]]
+; CHECK-NEXT:    br i1 [[EXITCOND_NOT_PEEL]], label [[FOR_COND_CLEANUP_LOOPEXIT:%.*]], label [[FOR_BODY_PEEL_NEXT:%.*]]
+; CHECK:       for.body.peel.next:
+; CHECK-NEXT:    br label [[FOR_BODY_PEEL2:%.*]]
+; CHECK:       for.body.peel2:
+; CHECK-NEXT:    [[COND_PEEL3:%.*]] = tail call i32 @llvm.umax.i32(i32 [[INC_PEEL]], i32 2)
+; CHECK-NEXT:    tail call void @foo(i32 [[COND_PEEL3]])
+; CHECK-NEXT:    [[INC_PEEL4:%.*]] = add nuw i32 [[INC_PEEL]], 1
+; CHECK-NEXT:    [[EXITCOND_NOT_PEEL5:%.*]] = icmp eq i32 [[INC_PEEL4]], [[N]]
+; CHECK-NEXT:    br i1 [[EXITCOND_NOT_PEEL5]], label [[FOR_COND_CLEANUP_LOOPEXIT]], label [[FOR_BODY_PEEL_NEXT1:%.*]]
+; CHECK:       for.body.peel.next1:
+; CHECK-NEXT:    br label [[FOR_BODY_PEEL_NEXT6:%.*]]
+; CHECK:       for.body.peel.next6:
+; CHECK-NEXT:    br label [[FOR_BODY_PREHEADER_PEEL_NEWPH:%.*]]
+; CHECK:       for.body.preheader.peel.newph:
 ; CHECK-NEXT:    br label [[FOR_BODY:%.*]]
 ; CHECK:       for.body:
-; CHECK-NEXT:    [[I_06:%.*]] = phi i32 [ [[INC:%.*]], [[FOR_BODY]] ], [ 0, [[FOR_BODY_PREHEADER]] ]
-; CHECK-NEXT:    [[COND:%.*]] = tail call i32 @llvm.umax.i32(i32 [[I_06]], i32 2)
-; CHECK-NEXT:    tail call void @foo(i32 [[COND]])
+; CHECK-NEXT:    [[I_06:%.*]] = phi i32 [ [[INC:%.*]], [[FOR_BODY]] ], [ [[INC_PEEL4]], [[FOR_BODY_PREHEADER_PEEL_NEWPH]] ]
+; CHECK-NEXT:    tail call void @foo(i32 [[I_06]])
 ; CHECK-NEXT:    [[INC]] = add nuw i32 [[I_06]], 1
 ; CHECK-NEXT:    [[EXITCOND_NOT:%.*]] = icmp eq i32 [[INC]], [[N]]
-; CHECK-NEXT:    br i1 [[EXITCOND_NOT]], label [[FOR_COND_CLEANUP_LOOPEXIT:%.*]], label [[FOR_BODY]]
+; CHECK-NEXT:    br i1 [[EXITCOND_NOT]], label [[FOR_COND_CLEANUP_LOOPEXIT_LOOPEXIT:%.*]], label [[FOR_BODY]], !llvm.loop [[LOOP2:![0-9]+]]
+; CHECK:       for.cond.cleanup.loopexit.loopexit:
+; CHECK-NEXT:    br label [[FOR_COND_CLEANUP_LOOPEXIT]]
 ; CHECK:       for.cond.cleanup.loopexit:
 ; CHECK-NEXT:    br label [[FOR_COND_CLEANUP]]
 ; CHECK:       for.cond.cleanup:
@@ -87,14 +133,37 @@ define void @test3(i32 %N) {
 ; CHECK-NEXT:    [[CMP5:%.*]] = icmp slt i32 [[N]], 0
 ; CHECK-NEXT:    br i1 [[CMP5]], label [[FOR_BODY_PREHEADER:%.*]], label [[FOR_COND_CLEANUP:%.*]]
 ; CHECK:       for.body.preheader:
+; CHECK-NEXT:    br label [[FOR_BODY_PEEL_BEGIN:%.*]]
+; CHECK:       for.body.peel.begin:
+; CHECK-NEXT:    br label [[FOR_BODY_PEEL:%.*]]
+; CHECK:       for.body.peel:
+; CHECK-NEXT:    [[COND_PEEL:%.*]] = tail call i32 @llvm.smax.i32(i32 0, i32 -2)
+; CHECK-NEXT:    tail call void @foo(i32 [[COND_PEEL]])
+; CHECK-NEXT:    [[DEC_PEEL:%.*]] = add nsw i32 0, -1
+; CHECK-NEXT:    [[CMP_PEEL:%.*]] = icmp sgt i32 [[DEC_PEEL]], [[N]]
+; CHECK-NEXT:    br i1 [[CMP_PEEL]], label [[FOR_BODY_PEEL_NEXT:%.*]], label [[FOR_COND_CLEANUP_LOOPEXIT:%.*]]
+; CHECK:       for.body.peel.next:
+; CHECK-NEXT:    br label [[FOR_BODY_PEEL2:%.*]]
+; CHECK:       for.body.peel2:
+; CHECK-NEXT:    [[COND_PEEL3:%.*]] = tail call i32 @llvm.smax.i32(i32 [[DEC_PEEL]], i32 -2)
+; CHECK-NEXT:    tail call void @foo(i32 [[COND_PEEL3]])
+; CHECK-NEXT:    [[DEC_PEEL4:%.*]] = add nsw i32 [[DEC_PEEL]], -1
+; CHECK-NEXT:    [[CMP_PEEL5:%.*]] = icmp sgt i32 [[DEC_PEEL4]], [[N]]
+; CHECK-NEXT:    br i1 [[CMP_PEEL5]], label [[FOR_BODY_PEEL_NEXT1:%.*]], label [[FOR_COND_CLEANUP_LOOPEXIT]]
+; CHECK:       for.body.peel.next1:
+; CHECK-NEXT:    br label [[FOR_BODY_PEEL_NEXT6:%.*]]
+; CHECK:       for.body.peel.next6:
+; CHECK-NEXT:    br label [[FOR_BODY_PREHEADER_PEEL_NEWPH:%.*]]
+; CHECK:       for.body.preheader.peel.newph:
 ; CHECK-NEXT:    br label [[FOR_BODY:%.*]]
 ; CHECK:       for.body:
-; CHECK-NEXT:    [[I_06:%.*]] = phi i32 [ [[DEC:%.*]], [[FOR_BODY]] ], [ 0, [[FOR_BODY_PREHEADER]] ]
-; CHECK-NEXT:    [[COND:%.*]] = tail call i32 @llvm.smax.i32(i32 [[I_06]], i32 -2)
-; CHECK-NEXT:    tail call void @foo(i32 [[COND]])
+; CHECK-NEXT:    [[I_06:%.*]] = phi i32 [ [[DEC:%.*]], [[FOR_BODY]] ], [ [[DEC_PEEL4]], [[FOR_BODY_PREHEADER_PEEL_NEWPH]] ]
+; CHECK-NEXT:    tail call void @foo(i32 -2)
 ; CHECK-NEXT:    [[DEC]] = add nsw i32 [[I_06]], -1
 ; CHECK-NEXT:    [[CMP:%.*]] = icmp sgt i32 [[DEC]], [[N]]
-; CHECK-NEXT:    br i1 [[CMP]], label [[FOR_BODY]], label [[FOR_COND_CLEANUP_LOOPEXIT:%.*]]
+; CHECK-NEXT:    br i1 [[CMP]], label [[FOR_BODY]], label [[FOR_COND_CLEANUP_LOOPEXIT_LOOPEXIT:%.*]], !llvm.loop [[LOOP3:![0-9]+]]
+; CHECK:       for.cond.cleanup.loopexit.loopexit:
+; CHECK-NEXT:    br label [[FOR_COND_CLEANUP_LOOPEXIT]]
 ; CHECK:       for.cond.cleanup.loopexit:
 ; CHECK-NEXT:    br label [[FOR_COND_CLEANUP]]
 ; CHECK:       for.cond.cleanup:
@@ -123,14 +192,37 @@ define void @test4(i32 %N) {
 ; CHECK-NEXT:    [[CMP5:%.*]] = icmp slt i32 [[N]], 0
 ; CHECK-NEXT:    br i1 [[CMP5]], label [[FOR_BODY_PREHEADER:%.*]], label [[FOR_COND_CLEANUP:%.*]]
 ; CHECK:       for.body.preheader:
+; CHECK-NEXT:    br label [[FOR_BODY_PEEL_BEGIN:%.*]]
+; CHECK:       for.body.peel.begin:
+; CHECK-NEXT:    br label [[FOR_BODY_PEEL:%.*]]
+; CHECK:       for.body.peel:
+; CHECK-NEXT:    [[COND_PEEL:%.*]] = tail call i32 @llvm.smin.i32(i32 0, i32 -2)
+; CHECK-NEXT:    tail call void @foo(i32 noundef signext [[COND_PEEL]])
+; CHECK-NEXT:    [[DEC_PEEL:%.*]] = add nsw i32 0, -1
+; CHECK-NEXT:    [[CMP_PEEL:%.*]] = icmp sgt i32 [[DEC_PEEL]], [[N]]
+; CHECK-NEXT:    br i1 [[CMP_PEEL]], label [[FOR_BODY_PEEL_NEXT:%.*]], label [[FOR_COND_CLEANUP_LOOPEXIT:%.*]]
+; CHECK:       for.body.peel.next:
+; CHECK-NEXT:    br label [[FOR_BODY_PEEL2:%.*]]
+; CHECK:       for.body.peel2:
+; CHECK-NEXT:    [[COND_PEEL3:%.*]] = tail call i32 @llvm.smin.i32(i32 [[DEC_PEEL]], i32 -2)
+; CHECK-NEXT:    tail call void @foo(i32 noundef signext [[COND_PEEL3]])
+; CHECK-NEXT:    [[DEC_PEEL4:%.*]] = add nsw i32 [[DEC_PEEL]], -1
+; CHECK-NEXT:    [[CMP_PEEL5:%.*]] = icmp sgt i32 [[DEC_PEEL4]], [[N]]
+; CHECK-NEXT:    br i1 [[CMP_PEEL5]], label [[FOR_BODY_PEEL_NEXT1:%.*]], label [[FOR_COND_CLEANUP_LOOPEXIT]]
+; CHECK:       for.body.peel.next1:
+; CHECK-NEXT:    br label [[FOR_BODY_PEEL_NEXT6:%.*]]
+; CHECK:       for.body.peel.next6:
+; CHECK-NEXT:    br label [[FOR_BODY_PREHEADER_PEEL_NEWPH:%.*]]
+; CHECK:       for.body.preheader.peel.newph:
 ; CHECK-NEXT:    br label [[FOR_BODY:%.*]]
 ; CHECK:       for.body:
-; CHECK-NEXT:    [[I_06:%.*]] = phi i32 [ [[DEC:%.*]], [[FOR_BODY]] ], [ 0, [[FOR_BODY_PREHEADER]] ]
-; CHECK-NEXT:    [[COND:%.*]] = tail call i32 @llvm.smin.i32(i32 [[I_06]], i32 -2)
-; CHECK-NEXT:    tail call void @foo(i32 noundef signext [[COND]])
+; CHECK-NEXT:    [[I_06:%.*]] = phi i32 [ [[DEC:%.*]], [[FOR_BODY]] ], [ [[DEC_PEEL4]], [[FOR_BODY_PREHEADER_PEEL_NEWPH]] ]
+; CHECK-NEXT:    tail call void @foo(i32 noundef signext [[I_06]])
 ; CHECK-NEXT:    [[DEC]] = add nsw i32 [[I_06]], -1
 ; CHECK-NEXT:    [[CMP:%.*]] = icmp sgt i32 [[DEC]], [[N]]
-; CHECK-NEXT:    br i1 [[CMP]], label [[FOR_BODY]], label [[FOR_COND_CLEANUP_LOOPEXIT:%.*]]
+; CHECK-NEXT:    br i1 [[CMP]], label [[FOR_BODY]], label [[FOR_COND_CLEANUP_LOOPEXIT_LOOPEXIT:%.*]], !llvm.loop [[LOOP4:![0-9]+]]
+; CHECK:       for.cond.cleanup.loopexit.loopexit:
+; CHECK-NEXT:    br label [[FOR_COND_CLEANUP_LOOPEXIT]]
 ; CHECK:       for.cond.cleanup.loopexit:
 ; CHECK-NEXT:    br label [[FOR_COND_CLEANUP]]
 ; CHECK:       for.cond.cleanup:
@@ -187,3 +279,10 @@ for.body:
 for.cond.cleanup:
   ret void
 }
+;.
+; CHECK: [[LOOP0]] = distinct !{[[LOOP0]], [[META1:![0-9]+]]}
+; CHECK: [[META1]] = !{!"llvm.loop.peeled.count", i32 2}
+; CHECK: [[LOOP2]] = distinct !{[[LOOP2]], [[META1]]}
+; CHECK: [[LOOP3]] = distinct !{[[LOOP3]], [[META1]]}
+; CHECK: [[LOOP4]] = distinct !{[[LOOP4]], [[META1]]}
+;.



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