df8956442f
In https://reviews.llvm.org/D129599, non-trivial switching was disabled for cold loops in the interest of code size. This added a dependency on BlockFrequencyInfo with PGO, but in loop passes this is only available on a lossy basis: see https://reviews.llvm.org/D86156 LICM moved away from BFI so as of today SimpleLoopUnswitch is the only remaining loop pass that uses BFI, for the sole reason to prevent code size increases in PGO builds. It doesn't use BFI if there's no profile summary available. After some investigation on llvm-test-suite it turns out that the lossy BFI causes very significant deviations in block frequency, since when new loops are deleted/created during the loop pass manager it can return frequencies for different loops altogether. This results in unswitchable loops being mistakenly skipped because they are thought to be cold. This patch removes the use of BFI from SimpleLoopUnswitch and thus the last remaining use of BFI in a loop pass. To recover the original intent of not unswitching cold code, PGOForceFunctionAttrs can be used to annotate functions which can be optimized for code size, since SimpleLoopUnswitch will respect OptSize: https://reviews.llvm.org/D94559 This isn't 100% the same behaviour since the previous behaviour checked for coldness at the loop level and this is now at the function level. We could expand PGOForceFunctionAttrs to be more granular at the loop level, https://github.com/llvm/llvm-project/issues/159595 tracks this idea.
126 lines
5.6 KiB
LLVM
126 lines
5.6 KiB
LLVM
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 2
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; RUN: opt < %s -passes='pgo-force-function-attrs,function(loop-mssa(simple-loop-unswitch<nontrivial>))' -pgo-kind=pgo-instr-use-pipeline -pgo-cold-func-opt=optsize -S | FileCheck %s
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; RUN: opt < %s -passes='pgo-force-function-attrs,function(loop-mssa(simple-loop-unswitch<nontrivial>))' -pgo-kind=pgo-instr-use-pipeline -pgo-cold-func-opt=minsize -S | FileCheck %s
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;; Check that non-trivial loop unswitching is not applied to a cold loop in a
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;; cold loop nest.
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;; IR was generated from the following loop nest, profiled when called
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;; with M=0 and N=0.
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;; void function(bool cond, int M, int N, int * A, int *B, int *C) {
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;; for (unsigned j = 0; j < M; j++)
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;; for (unsigned i=0; i < N; i++) {
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;; A[i] = B[i] + C[i];
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;; if (cond) do_something();
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;; }
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;; }
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define void @_Z11functionbiiPiS_S_(i1 %cond, i32 %M, i32 %N, ptr %A, ptr %B, ptr %C) !prof !36 {
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; CHECK-LABEL: define void @_Z11functionbiiPiS_S_
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; CHECK-SAME: (i1 [[COND:%.*]], i32 [[M:%.*]], i32 [[N:%.*]], ptr [[A:%.*]], ptr [[B:%.*]], ptr [[C:%.*]]) {{.*}}{
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; CHECK-NEXT: entry:
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; CHECK-NEXT: [[CMP19_NOT:%.*]] = icmp eq i32 [[M]], 0
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; CHECK-NEXT: br i1 [[CMP19_NOT]], label [[FOR_COND_CLEANUP:%.*]], label [[FOR_COND1_PREHEADER_LR_PH:%.*]], !prof [[PROF17:![0-9]+]]
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; CHECK: for.cond1.preheader.lr.ph:
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; CHECK-NEXT: [[CMP217_NOT:%.*]] = icmp eq i32 [[N]], 0
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; CHECK-NEXT: br label [[FOR_COND1_PREHEADER:%.*]]
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; CHECK: for.cond1.preheader:
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; CHECK-NEXT: [[J_020:%.*]] = phi i32 [ 0, [[FOR_COND1_PREHEADER_LR_PH]] ], [ [[INC10:%.*]], [[FOR_COND_CLEANUP3:%.*]] ]
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; CHECK-NEXT: br i1 [[CMP217_NOT]], label [[FOR_COND_CLEANUP3]], label [[FOR_BODY4_PREHEADER:%.*]]
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; CHECK: for.body4.preheader:
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; CHECK-NEXT: br label [[FOR_BODY4:%.*]]
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; CHECK: for.cond.cleanup.loopexit:
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; CHECK-NEXT: br label [[FOR_COND_CLEANUP]]
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; CHECK: for.cond.cleanup:
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; CHECK-NEXT: ret void
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; CHECK: for.cond.cleanup3.loopexit:
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; CHECK-NEXT: br label [[FOR_COND_CLEANUP3]]
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; CHECK: for.cond.cleanup3:
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; CHECK-NEXT: [[INC10]] = add nuw i32 [[J_020]], 1
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; CHECK-NEXT: [[EXITCOND22_NOT:%.*]] = icmp eq i32 [[INC10]], [[M]]
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; CHECK-NEXT: br i1 [[EXITCOND22_NOT]], label [[FOR_COND_CLEANUP_LOOPEXIT:%.*]], label [[FOR_COND1_PREHEADER]], !prof [[PROF17]]
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; CHECK: for.body4:
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; CHECK-NEXT: [[INDVARS_IV:%.*]] = phi i64 [ [[INDVARS_IV_NEXT:%.*]], [[FOR_INC:%.*]] ], [ 0, [[FOR_BODY4_PREHEADER]] ]
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; CHECK-NEXT: [[ARRAYIDX:%.*]] = getelementptr inbounds i32, ptr [[B]], i64 [[INDVARS_IV]]
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; CHECK-NEXT: [[TMP0:%.*]] = load i32, ptr [[ARRAYIDX]], align 4
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; CHECK-NEXT: [[ARRAYIDX6:%.*]] = getelementptr inbounds i32, ptr [[C]], i64 [[INDVARS_IV]]
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; CHECK-NEXT: [[TMP1:%.*]] = load i32, ptr [[ARRAYIDX6]], align 4
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; CHECK-NEXT: [[ADD:%.*]] = add nsw i32 [[TMP1]], [[TMP0]]
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; CHECK-NEXT: [[ARRAYIDX8:%.*]] = getelementptr inbounds i32, ptr [[A]], i64 [[INDVARS_IV]]
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; CHECK-NEXT: store i32 [[ADD]], ptr [[ARRAYIDX8]], align 4
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; CHECK-NEXT: br i1 [[COND]], label [[IF_THEN:%.*]], label [[FOR_INC]]
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; CHECK: if.then:
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; CHECK-NEXT: tail call void @_Z12do_somethingv()
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; CHECK-NEXT: br label [[FOR_INC]]
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; CHECK: for.inc:
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; CHECK-NEXT: [[WIDE_TRIP_COUNT:%.*]] = zext i32 [[N]] to i64
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; CHECK-NEXT: [[INDVARS_IV_NEXT]] = add nuw nsw i64 [[INDVARS_IV]], 1
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; CHECK-NEXT: [[EXITCOND_NOT:%.*]] = icmp eq i64 [[INDVARS_IV_NEXT]], [[WIDE_TRIP_COUNT]]
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; CHECK-NEXT: br i1 [[EXITCOND_NOT]], label [[FOR_COND_CLEANUP3_LOOPEXIT:%.*]], label [[FOR_BODY4]]
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;
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entry:
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%cmp19.not = icmp eq i32 %M, 0
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br i1 %cmp19.not, label %for.cond.cleanup, label %for.cond1.preheader.lr.ph, !prof !37
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for.cond1.preheader.lr.ph:
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%cmp217.not = icmp eq i32 %N, 0
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br label %for.cond1.preheader
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for.cond1.preheader:
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%j.020 = phi i32 [ 0, %for.cond1.preheader.lr.ph ], [ %inc10, %for.cond.cleanup3 ]
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br i1 %cmp217.not, label %for.cond.cleanup3, label %for.body4
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for.cond.cleanup:
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ret void
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for.cond.cleanup3:
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%inc10 = add nuw i32 %j.020, 1
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%exitcond22.not = icmp eq i32 %inc10, %M
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br i1 %exitcond22.not, label %for.cond.cleanup, label %for.cond1.preheader, !prof !37
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for.body4:
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%indvars.iv = phi i64 [ %indvars.iv.next, %for.inc ], [ 0, %for.cond1.preheader ]
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%arrayidx = getelementptr inbounds i32, ptr %B, i64 %indvars.iv
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%0 = load i32, ptr %arrayidx, align 4
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%arrayidx6 = getelementptr inbounds i32, ptr %C, i64 %indvars.iv
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%1 = load i32, ptr %arrayidx6, align 4
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%add = add nsw i32 %1, %0
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%arrayidx8 = getelementptr inbounds i32, ptr %A, i64 %indvars.iv
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store i32 %add, ptr %arrayidx8, align 4
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br i1 %cond, label %if.then, label %for.inc
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if.then:
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tail call void @_Z12do_somethingv()
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br label %for.inc
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for.inc:
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%wide.trip.count = zext i32 %N to i64
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%indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
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%exitcond.not = icmp eq i64 %indvars.iv.next, %wide.trip.count
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br i1 %exitcond.not, label %for.cond.cleanup3, label %for.body4
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}
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declare void @_Z12do_somethingv()
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!llvm.module.flags = !{!6}
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!6 = !{i32 1, !"ProfileSummary", !7}
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!7 = !{!8, !9, !10, !11, !12, !13, !14, !15, !16, !17}
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!8 = !{!"ProfileFormat", !"InstrProf"}
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!9 = !{!"TotalCount", i64 1002}
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!10 = !{!"MaxCount", i64 1000}
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!11 = !{!"MaxInternalCount", i64 1000}
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!12 = !{!"MaxFunctionCount", i64 1}
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!13 = !{!"NumCounts", i64 6}
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!14 = !{!"NumFunctions", i64 3}
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!15 = !{!"IsPartialProfile", i64 0}
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!16 = !{!"PartialProfileRatio", double 0.000000e+00}
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!17 = !{!"DetailedSummary", !18}
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!18 = !{!19, !31, !34}
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!19 = !{i32 10000, i64 1000, i32 1}
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!31 = !{i32 999000, i64 1000, i32 1}
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!34 = !{i32 999999, i64 1, i32 3}
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!36 = !{!"function_entry_count", i64 1}
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!37 = !{!"branch_weights", i32 1, i32 0}
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