[LoopInterchange] Don't consider loops with BTC=0 #167113
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@@ -46,6 +46,7 @@ | |
| #include "llvm/Transforms/Utils/Local.h" | ||
| #include "llvm/Transforms/Utils/LoopUtils.h" | ||
| #include <cassert> | ||
| #include <map> | ||
| #include <utility> | ||
| #include <vector> | ||
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@@ -1462,6 +1463,25 @@ std::optional<bool> LoopInterchangeProfitability::isProfitableForVectorization( | |
| bool LoopInterchangeProfitability::isProfitable( | ||
| const Loop *InnerLoop, const Loop *OuterLoop, unsigned InnerLoopId, | ||
| unsigned OuterLoopId, CharMatrix &DepMatrix, CacheCostManager &CCM) { | ||
| // A loop with a backedge that isn't taken, e.g. an unconditional branch | ||
| // true, isn't really a loop and we don't want to consider it as a | ||
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| // candidate. | ||
| // TODO: when interchange is forced, we should probably also allow | ||
| // interchange for these loops, and thus this logic should be moved just | ||
| // below the cost-model ignore check below. But this check is done first | ||
| // to avoid the issue in #163954. | ||
| const SCEV *InnerBTC = SE->getBackedgeTakenCount(InnerLoop); | ||
| const SCEV *OuterBTC = SE->getBackedgeTakenCount(OuterLoop); | ||
| if (InnerBTC && InnerBTC->isZero()) { | ||
| LLVM_DEBUG(dbgs() << "Inner loop back-edge isn't taken, rejecting " | ||
| "single iteration loop\n"); | ||
| return false; | ||
| } | ||
| if (OuterBTC && OuterBTC->isZero()) { | ||
| LLVM_DEBUG(dbgs() << "Outer loop back-edge isn't taken, rejecting " | ||
| "single iteration loop\n"); | ||
| return false; | ||
| } | ||
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| // Return true if interchange is forced and the cost-model ignored. | ||
| if (Profitabilities.size() == 1 && Profitabilities[0] == RuleTy::Ignore) | ||
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| @@ -0,0 +1,74 @@ | ||
| ; RUN: opt < %s -passes=loop-interchange -verify-dom-info -verify-loop-info \ | ||
| ; RUN: -pass-remarks-output=%t -pass-remarks='loop-interchange' -S | ||
| ; RUN: cat %t | FileCheck %s | ||
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| target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128" | ||
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| @D = common global [100 x [100 x [100 x i32]]] zeroinitializer | ||
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| ; The outer loop's backedge isn't taken. Check the loop with BTC=0 is considered | ||
| ; unprofitable, but that we still interchange the two inner loops. | ||
| ; | ||
| ; for(int i=0;i<1;i++) | ||
| ; for(int j=0;j<100;j++) | ||
| ; for(int k=0;k<100;k++) | ||
| ; D[i][k][j] = D[i][k][j]+t; | ||
| ; | ||
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| ; CHECK: --- !Analysis | ||
| ; CHECK-NEXT: Pass: loop-interchange | ||
| ; CHECK-NEXT: Name: Dependence | ||
| ; CHECK-NEXT: Function: interchange_i_and_j | ||
| ; CHECK-NEXT: Args: | ||
| ; CHECK-NEXT: - String: Computed dependence info, invoking the transform. | ||
| ; CHECK-NEXT: ... | ||
| ; CHECK-NEXT: --- !Passed | ||
| ; CHECK-NEXT: Pass: loop-interchange | ||
| ; CHECK-NEXT: Name: Interchanged | ||
| ; CHECK-NEXT: Function: interchange_i_and_j | ||
| ; CHECK-NEXT: Args: | ||
| ; CHECK-NEXT: - String: Loop interchanged with enclosing loop. | ||
| ; CHECK-NEXT: ... | ||
| ; CHECK-NEXT: --- !Missed | ||
| ; CHECK-NEXT: Pass: loop-interchange | ||
| ; CHECK-NEXT: Name: InterchangeNotProfitable | ||
| ; CHECK-NEXT: Function: interchange_i_and_j | ||
| ; CHECK-NEXT: Args: | ||
| ; CHECK-NEXT: - String: Insufficient information to calculate the cost of loop for interchange. | ||
| ; CHECK-NEXT: ... | ||
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| define void @interchange_i_and_j(i32 %t){ | ||
| entry: | ||
| br label %outer.header | ||
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| outer.header: | ||
| %i = phi i64 [ 0, %entry ], [ %inc16, %for.inc15 ] | ||
| br label %inner1.header | ||
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| inner1.header: | ||
| %j = phi i64 [ 0, %outer.header ], [ %inc13, %for.inc12 ] | ||
| br label %inner2.body | ||
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| inner2.body: | ||
| %k = phi i64 [ 0, %inner1.header ], [ %inc, %inner2.body ] | ||
| %arrayidx8 = getelementptr inbounds [100 x [100 x i32]], ptr @D, i64 %i, i64 %k, i64 %j | ||
| %0 = load i32, ptr %arrayidx8 | ||
| %add = add nsw i32 %0, %t | ||
| store i32 %add, ptr %arrayidx8 | ||
| %inc = add nuw nsw i64 %k, 1 | ||
| %exitcond = icmp eq i64 %inc, 100 | ||
| br i1 %exitcond, label %for.inc12, label %inner2.body | ||
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| for.inc12: | ||
| %inc13 = add nuw nsw i64 %j, 1 | ||
| %exitcond29 = icmp eq i64 %inc13, 100 | ||
| br i1 %exitcond29, label %for.inc15, label %inner1.header | ||
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| for.inc15: | ||
| %inc16 = add nuw nsw i64 %i, 1 | ||
| %exitcond30 = icmp eq i64 %inc16, 1 | ||
| br i1 %exitcond30, label %for.end17, label %outer.header | ||
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| for.end17: | ||
| ret void | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,54 @@ | ||
| ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 6 | ||
| ; RUN: opt < %s -passes=loop-interchange -loop-interchange-profitabilities=ignore -cache-line-size=64 -verify-dom-info -verify-loop-info -verify-scev -verify-loop-lcssa -S | FileCheck %s | ||
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| ; Test case for issue: https://github.com/llvm/llvm-project/issues/163954 | ||
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| define void @test() { | ||
| ; CHECK-LABEL: define void @test() { | ||
| ; CHECK-NEXT: [[ENTRY:.*]]: | ||
| ; CHECK-NEXT: br label %[[OUTER_HEADER:.*]] | ||
| ; CHECK: [[OUTER_HEADER]]: | ||
| ; CHECK-NEXT: [[I:%.*]] = phi i8 [ 0, %[[ENTRY]] ], [ [[DOTLCSSA:%.*]], %[[OUTER_LATCH:.*]] ] | ||
| ; CHECK-NEXT: br label %[[INNER_HEADER:.*]] | ||
| ; CHECK: [[INNER_HEADER]]: | ||
| ; CHECK-NEXT: [[J:%.*]] = phi i64 [ 0, %[[OUTER_HEADER]] ], [ [[J_NEXT:%.*]], %[[INNER_LATCH:.*]] ] | ||
| ; CHECK-NEXT: [[TMP0:%.*]] = phi i8 [ [[I]], %[[OUTER_HEADER]] ], [ [[TMP1:%.*]], %[[INNER_LATCH]] ] | ||
| ; CHECK-NEXT: br label %[[INNER_BODY:.*]] | ||
| ; CHECK: [[INNER_BODY]]: | ||
| ; CHECK-NEXT: br i1 true, label %[[INNER_LATCH]], label %[[INNER_BODY]] | ||
| ; CHECK: [[INNER_LATCH]]: | ||
| ; CHECK-NEXT: [[TMP1]] = or i8 [[TMP0]], 0 | ||
| ; CHECK-NEXT: [[J_NEXT]] = add i64 [[J]], 1 | ||
| ; CHECK-NEXT: br i1 true, label %[[OUTER_LATCH]], label %[[INNER_HEADER]] | ||
| ; CHECK: [[OUTER_LATCH]]: | ||
| ; CHECK-NEXT: [[DOTLCSSA]] = phi i8 [ [[TMP1]], %[[INNER_LATCH]] ] | ||
| ; CHECK-NEXT: br i1 true, label %[[EXIT:.*]], label %[[OUTER_HEADER]] | ||
| ; CHECK: [[EXIT]]: | ||
| ; CHECK-NEXT: ret void | ||
| ; | ||
| entry: | ||
| br label %outer.header | ||
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| outer.header: | ||
| %i = phi i8 [ 0, %entry ], [ %1, %outer.latch ] | ||
| br label %inner.header | ||
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| inner.header: | ||
| %j = phi i64 [ 0, %outer.header ], [ %j.next, %inner.latch ] | ||
| %0 = phi i8 [ %i, %outer.header ], [ %1, %inner.latch ] | ||
| br label %inner.body | ||
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| inner.body: | ||
| br i1 true, label %inner.latch, label %inner.body ; another (self) loop, but never taken | ||
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| inner.latch: | ||
| %1 = or i8 %0, 0 | ||
| %j.next = add i64 %j, 1 | ||
| br i1 true, label %outer.latch, label %inner.header | ||
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| outer.latch: | ||
| br i1 true, label %exit, label %outer.header | ||
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| exit: | ||
| ret void | ||
| } |
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Maybe unnecessary?