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clang-p2996/llvm/test/Transforms/LoopUnroll/runtime-loop5.ll
Nikita Popov b9808e5660 [LoopUnroll] Fold add chains during unrolling 
Loop unrolling tends to produce chains of
`%x1 = add %x0, 1; %x2 = add %x1, 1; ...` with one add per unrolled
iteration. This patch simplifies these adds to `%xN = add %x0, N`
directly during unrolling, rather than waiting for InstCombine to do so.

The motivation for this is that having a single add (rather than
an add chain) on the induction variable makes it a simple recurrence,
which we specially recognize in a number of places. This allows
InstCombine to directly perform folds with that knowledge, instead
of first folding the add chains, and then doing other folds in another
InstCombine iteration.

Due to the reduced number of InstCombine iterations, this also
results in a small compile-time improvement.

Differential Revision: https://reviews.llvm.org/D153540
2023-07-05 09:54:28 +02:00

154 lines
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; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt < %s -S -passes=loop-unroll -unroll-runtime=true -unroll-count=16 | FileCheck --check-prefix=UNROLL-16 %s
; RUN: opt < %s -S -passes=loop-unroll -unroll-runtime=true -unroll-count=4 | FileCheck --check-prefix=UNROLL-4 %s
; RUN: opt < %s -S -passes='require<opt-remark-emit>,loop-unroll' -unroll-runtime=true -unroll-count=16 | FileCheck --check-prefix=UNROLL-16 %s
; RUN: opt < %s -S -passes='require<opt-remark-emit>,loop-unroll' -unroll-runtime=true -unroll-count=4 | FileCheck --check-prefix=UNROLL-4 %s
; Given that the trip-count of this loop is a 3-bit value, we cannot
; safely unroll it with a count of anything more than 8.
define i3 @test(ptr %a, i3 %n) {
; UNROLL-16-LABEL: @test(
; UNROLL-16-NEXT: entry:
; UNROLL-16-NEXT: [[CMP1:%.*]] = icmp eq i3 [[N:%.*]], 0
; UNROLL-16-NEXT: br i1 [[CMP1]], label [[FOR_END:%.*]], label [[FOR_BODY_PREHEADER:%.*]]
; UNROLL-16: for.body.preheader:
; UNROLL-16-NEXT: br label [[FOR_BODY:%.*]]
; UNROLL-16: for.body:
; UNROLL-16-NEXT: [[TMP0:%.*]] = load i3, ptr [[A:%.*]], align 1
; UNROLL-16-NEXT: [[EXITCOND:%.*]] = icmp eq i3 1, [[N]]
; UNROLL-16-NEXT: br i1 [[EXITCOND]], label [[FOR_END_LOOPEXIT:%.*]], label [[FOR_BODY_1:%.*]]
; UNROLL-16: for.body.1:
; UNROLL-16-NEXT: [[ARRAYIDX_1:%.*]] = getelementptr inbounds i3, ptr [[A]], i64 1
; UNROLL-16-NEXT: [[TMP1:%.*]] = load i3, ptr [[ARRAYIDX_1]], align 1
; UNROLL-16-NEXT: [[ADD_1:%.*]] = add nsw i3 [[TMP1]], [[TMP0]]
; UNROLL-16-NEXT: [[EXITCOND_1:%.*]] = icmp eq i3 2, [[N]]
; UNROLL-16-NEXT: br i1 [[EXITCOND_1]], label [[FOR_END_LOOPEXIT]], label [[FOR_BODY_2:%.*]]
; UNROLL-16: for.body.2:
; UNROLL-16-NEXT: [[ARRAYIDX_2:%.*]] = getelementptr inbounds i3, ptr [[A]], i64 2
; UNROLL-16-NEXT: [[TMP2:%.*]] = load i3, ptr [[ARRAYIDX_2]], align 1
; UNROLL-16-NEXT: [[ADD_2:%.*]] = add nsw i3 [[TMP2]], [[ADD_1]]
; UNROLL-16-NEXT: [[EXITCOND_2:%.*]] = icmp eq i3 3, [[N]]
; UNROLL-16-NEXT: br i1 [[EXITCOND_2]], label [[FOR_END_LOOPEXIT]], label [[FOR_BODY_3:%.*]]
; UNROLL-16: for.body.3:
; UNROLL-16-NEXT: [[ARRAYIDX_3:%.*]] = getelementptr inbounds i3, ptr [[A]], i64 3
; UNROLL-16-NEXT: [[TMP3:%.*]] = load i3, ptr [[ARRAYIDX_3]], align 1
; UNROLL-16-NEXT: [[ADD_3:%.*]] = add nsw i3 [[TMP3]], [[ADD_2]]
; UNROLL-16-NEXT: [[EXITCOND_3:%.*]] = icmp eq i3 -4, [[N]]
; UNROLL-16-NEXT: br i1 [[EXITCOND_3]], label [[FOR_END_LOOPEXIT]], label [[FOR_BODY_4:%.*]]
; UNROLL-16: for.body.4:
; UNROLL-16-NEXT: [[ARRAYIDX_4:%.*]] = getelementptr inbounds i3, ptr [[A]], i64 4
; UNROLL-16-NEXT: [[TMP4:%.*]] = load i3, ptr [[ARRAYIDX_4]], align 1
; UNROLL-16-NEXT: [[ADD_4:%.*]] = add nsw i3 [[TMP4]], [[ADD_3]]
; UNROLL-16-NEXT: [[EXITCOND_4:%.*]] = icmp eq i3 -3, [[N]]
; UNROLL-16-NEXT: br i1 [[EXITCOND_4]], label [[FOR_END_LOOPEXIT]], label [[FOR_BODY_5:%.*]]
; UNROLL-16: for.body.5:
; UNROLL-16-NEXT: [[ARRAYIDX_5:%.*]] = getelementptr inbounds i3, ptr [[A]], i64 5
; UNROLL-16-NEXT: [[TMP5:%.*]] = load i3, ptr [[ARRAYIDX_5]], align 1
; UNROLL-16-NEXT: [[ADD_5:%.*]] = add nsw i3 [[TMP5]], [[ADD_4]]
; UNROLL-16-NEXT: [[EXITCOND_5:%.*]] = icmp eq i3 -2, [[N]]
; UNROLL-16-NEXT: br i1 [[EXITCOND_5]], label [[FOR_END_LOOPEXIT]], label [[FOR_BODY_6:%.*]]
; UNROLL-16: for.body.6:
; UNROLL-16-NEXT: [[ARRAYIDX_6:%.*]] = getelementptr inbounds i3, ptr [[A]], i64 6
; UNROLL-16-NEXT: [[TMP6:%.*]] = load i3, ptr [[ARRAYIDX_6]], align 1
; UNROLL-16-NEXT: [[ADD_6:%.*]] = add nsw i3 [[TMP6]], [[ADD_5]]
; UNROLL-16-NEXT: br label [[FOR_END_LOOPEXIT]]
; UNROLL-16: for.end.loopexit:
; UNROLL-16-NEXT: [[ADD_LCSSA:%.*]] = phi i3 [ [[TMP0]], [[FOR_BODY]] ], [ [[ADD_1]], [[FOR_BODY_1]] ], [ [[ADD_2]], [[FOR_BODY_2]] ], [ [[ADD_3]], [[FOR_BODY_3]] ], [ [[ADD_4]], [[FOR_BODY_4]] ], [ [[ADD_5]], [[FOR_BODY_5]] ], [ [[ADD_6]], [[FOR_BODY_6]] ]
; UNROLL-16-NEXT: br label [[FOR_END]]
; UNROLL-16: for.end:
; UNROLL-16-NEXT: [[SUM_0_LCSSA:%.*]] = phi i3 [ 0, [[ENTRY:%.*]] ], [ [[ADD_LCSSA]], [[FOR_END_LOOPEXIT]] ]
; UNROLL-16-NEXT: ret i3 [[SUM_0_LCSSA]]
;
; UNROLL-4-LABEL: @test(
; UNROLL-4-NEXT: entry:
; UNROLL-4-NEXT: [[CMP1:%.*]] = icmp eq i3 [[N:%.*]], 0
; UNROLL-4-NEXT: br i1 [[CMP1]], label [[FOR_END:%.*]], label [[FOR_BODY_PREHEADER:%.*]]
; UNROLL-4: for.body.preheader:
; UNROLL-4-NEXT: [[TMP0:%.*]] = add i3 [[N]], -1
; UNROLL-4-NEXT: [[XTRAITER:%.*]] = and i3 [[N]], 3
; UNROLL-4-NEXT: [[TMP1:%.*]] = icmp ult i3 [[TMP0]], 3
; UNROLL-4-NEXT: br i1 [[TMP1]], label [[FOR_END_LOOPEXIT_UNR_LCSSA:%.*]], label [[FOR_BODY_PREHEADER_NEW:%.*]]
; UNROLL-4: for.body.preheader.new:
; UNROLL-4-NEXT: [[UNROLL_ITER:%.*]] = sub i3 [[N]], [[XTRAITER]]
; UNROLL-4-NEXT: br label [[FOR_BODY:%.*]]
; UNROLL-4: for.body:
; UNROLL-4-NEXT: [[INDVARS_IV:%.*]] = phi i64 [ 0, [[FOR_BODY_PREHEADER_NEW]] ], [ [[INDVARS_IV_NEXT_3:%.*]], [[FOR_BODY]] ]
; UNROLL-4-NEXT: [[SUM_02:%.*]] = phi i3 [ 0, [[FOR_BODY_PREHEADER_NEW]] ], [ [[ADD_3:%.*]], [[FOR_BODY]] ]
; UNROLL-4-NEXT: [[NITER:%.*]] = phi i3 [ 0, [[FOR_BODY_PREHEADER_NEW]] ], [ [[NITER_NEXT_3:%.*]], [[FOR_BODY]] ]
; UNROLL-4-NEXT: [[ARRAYIDX:%.*]] = getelementptr inbounds i3, ptr [[A:%.*]], i64 [[INDVARS_IV]]
; UNROLL-4-NEXT: [[TMP2:%.*]] = load i3, ptr [[ARRAYIDX]], align 1
; UNROLL-4-NEXT: [[ADD:%.*]] = add nsw i3 [[TMP2]], [[SUM_02]]
; UNROLL-4-NEXT: [[INDVARS_IV_NEXT:%.*]] = add nuw nsw i64 [[INDVARS_IV]], 1
; UNROLL-4-NEXT: [[ARRAYIDX_1:%.*]] = getelementptr inbounds i3, ptr [[A]], i64 [[INDVARS_IV_NEXT]]
; UNROLL-4-NEXT: [[TMP3:%.*]] = load i3, ptr [[ARRAYIDX_1]], align 1
; UNROLL-4-NEXT: [[ADD_1:%.*]] = add nsw i3 [[TMP3]], [[ADD]]
; UNROLL-4-NEXT: [[INDVARS_IV_NEXT_1:%.*]] = add nuw nsw i64 [[INDVARS_IV]], 2
; UNROLL-4-NEXT: [[ARRAYIDX_2:%.*]] = getelementptr inbounds i3, ptr [[A]], i64 [[INDVARS_IV_NEXT_1]]
; UNROLL-4-NEXT: [[TMP4:%.*]] = load i3, ptr [[ARRAYIDX_2]], align 1
; UNROLL-4-NEXT: [[ADD_2:%.*]] = add nsw i3 [[TMP4]], [[ADD_1]]
; UNROLL-4-NEXT: [[INDVARS_IV_NEXT_2:%.*]] = add nuw nsw i64 [[INDVARS_IV]], 3
; UNROLL-4-NEXT: [[ARRAYIDX_3:%.*]] = getelementptr inbounds i3, ptr [[A]], i64 [[INDVARS_IV_NEXT_2]]
; UNROLL-4-NEXT: [[TMP5:%.*]] = load i3, ptr [[ARRAYIDX_3]], align 1
; UNROLL-4-NEXT: [[ADD_3]] = add nsw i3 [[TMP5]], [[ADD_2]]
; UNROLL-4-NEXT: [[INDVARS_IV_NEXT_3]] = add nuw nsw i64 [[INDVARS_IV]], 4
; UNROLL-4-NEXT: [[NITER_NEXT_3]] = add i3 [[NITER]], -4
; UNROLL-4-NEXT: [[NITER_NCMP_3:%.*]] = icmp eq i3 [[NITER_NEXT_3]], [[UNROLL_ITER]]
; UNROLL-4-NEXT: br i1 [[NITER_NCMP_3]], label [[FOR_END_LOOPEXIT_UNR_LCSSA_LOOPEXIT:%.*]], label [[FOR_BODY]], !llvm.loop [[LOOP0:![0-9]+]]
; UNROLL-4: for.end.loopexit.unr-lcssa.loopexit:
; UNROLL-4-NEXT: [[ADD_LCSSA_PH_PH:%.*]] = phi i3 [ [[ADD_3]], [[FOR_BODY]] ]
; UNROLL-4-NEXT: [[INDVARS_IV_UNR_PH:%.*]] = phi i64 [ [[INDVARS_IV_NEXT_3]], [[FOR_BODY]] ]
; UNROLL-4-NEXT: [[SUM_02_UNR_PH:%.*]] = phi i3 [ [[ADD_3]], [[FOR_BODY]] ]
; UNROLL-4-NEXT: br label [[FOR_END_LOOPEXIT_UNR_LCSSA]]
; UNROLL-4: for.end.loopexit.unr-lcssa:
; UNROLL-4-NEXT: [[ADD_LCSSA_PH:%.*]] = phi i3 [ undef, [[FOR_BODY_PREHEADER]] ], [ [[ADD_LCSSA_PH_PH]], [[FOR_END_LOOPEXIT_UNR_LCSSA_LOOPEXIT]] ]
; UNROLL-4-NEXT: [[INDVARS_IV_UNR:%.*]] = phi i64 [ 0, [[FOR_BODY_PREHEADER]] ], [ [[INDVARS_IV_UNR_PH]], [[FOR_END_LOOPEXIT_UNR_LCSSA_LOOPEXIT]] ]
; UNROLL-4-NEXT: [[SUM_02_UNR:%.*]] = phi i3 [ 0, [[FOR_BODY_PREHEADER]] ], [ [[SUM_02_UNR_PH]], [[FOR_END_LOOPEXIT_UNR_LCSSA_LOOPEXIT]] ]
; UNROLL-4-NEXT: [[LCMP_MOD:%.*]] = icmp ne i3 [[XTRAITER]], 0
; UNROLL-4-NEXT: br i1 [[LCMP_MOD]], label [[FOR_BODY_EPIL_PREHEADER:%.*]], label [[FOR_END_LOOPEXIT:%.*]]
; UNROLL-4: for.body.epil.preheader:
; UNROLL-4-NEXT: br label [[FOR_BODY_EPIL:%.*]]
; UNROLL-4: for.body.epil:
; UNROLL-4-NEXT: [[INDVARS_IV_EPIL:%.*]] = phi i64 [ [[INDVARS_IV_NEXT_EPIL:%.*]], [[FOR_BODY_EPIL]] ], [ [[INDVARS_IV_UNR]], [[FOR_BODY_EPIL_PREHEADER]] ]
; UNROLL-4-NEXT: [[SUM_02_EPIL:%.*]] = phi i3 [ [[ADD_EPIL:%.*]], [[FOR_BODY_EPIL]] ], [ [[SUM_02_UNR]], [[FOR_BODY_EPIL_PREHEADER]] ]
; UNROLL-4-NEXT: [[EPIL_ITER:%.*]] = phi i3 [ 0, [[FOR_BODY_EPIL_PREHEADER]] ], [ [[EPIL_ITER_NEXT:%.*]], [[FOR_BODY_EPIL]] ]
; UNROLL-4-NEXT: [[ARRAYIDX_EPIL:%.*]] = getelementptr inbounds i3, ptr [[A]], i64 [[INDVARS_IV_EPIL]]
; UNROLL-4-NEXT: [[TMP6:%.*]] = load i3, ptr [[ARRAYIDX_EPIL]], align 1
; UNROLL-4-NEXT: [[ADD_EPIL]] = add nsw i3 [[TMP6]], [[SUM_02_EPIL]]
; UNROLL-4-NEXT: [[INDVARS_IV_NEXT_EPIL]] = add i64 [[INDVARS_IV_EPIL]], 1
; UNROLL-4-NEXT: [[LFTR_WIDEIV_EPIL:%.*]] = trunc i64 [[INDVARS_IV_NEXT_EPIL]] to i3
; UNROLL-4-NEXT: [[EXITCOND_EPIL:%.*]] = icmp eq i3 [[LFTR_WIDEIV_EPIL]], [[N]]
; UNROLL-4-NEXT: [[EPIL_ITER_NEXT]] = add i3 [[EPIL_ITER]], 1
; UNROLL-4-NEXT: [[EPIL_ITER_CMP:%.*]] = icmp ne i3 [[EPIL_ITER_NEXT]], [[XTRAITER]]
; UNROLL-4-NEXT: br i1 [[EPIL_ITER_CMP]], label [[FOR_BODY_EPIL]], label [[FOR_END_LOOPEXIT_EPILOG_LCSSA:%.*]], !llvm.loop [[LOOP2:![0-9]+]]
; UNROLL-4: for.end.loopexit.epilog-lcssa:
; UNROLL-4-NEXT: [[ADD_LCSSA_PH1:%.*]] = phi i3 [ [[ADD_EPIL]], [[FOR_BODY_EPIL]] ]
; UNROLL-4-NEXT: br label [[FOR_END_LOOPEXIT]]
; UNROLL-4: for.end.loopexit:
; UNROLL-4-NEXT: [[ADD_LCSSA:%.*]] = phi i3 [ [[ADD_LCSSA_PH]], [[FOR_END_LOOPEXIT_UNR_LCSSA]] ], [ [[ADD_LCSSA_PH1]], [[FOR_END_LOOPEXIT_EPILOG_LCSSA]] ]
; UNROLL-4-NEXT: br label [[FOR_END]]
; UNROLL-4: for.end:
; UNROLL-4-NEXT: [[SUM_0_LCSSA:%.*]] = phi i3 [ 0, [[ENTRY:%.*]] ], [ [[ADD_LCSSA]], [[FOR_END_LOOPEXIT]] ]
; UNROLL-4-NEXT: ret i3 [[SUM_0_LCSSA]]
;
entry:
%cmp1 = icmp eq i3 %n, 0
br i1 %cmp1, label %for.end, label %for.body
for.body: ; preds = %for.body, %entry
%indvars.iv = phi i64 [ %indvars.iv.next, %for.body ], [ 0, %entry ]
%sum.02 = phi i3 [ %add, %for.body ], [ 0, %entry ]
%arrayidx = getelementptr inbounds i3, ptr %a, i64 %indvars.iv
%0 = load i3, ptr %arrayidx
%add = add nsw i3 %0, %sum.02
%indvars.iv.next = add i64 %indvars.iv, 1
%lftr.wideiv = trunc i64 %indvars.iv.next to i3
%exitcond = icmp eq i3 %lftr.wideiv, %n
br i1 %exitcond, label %for.end, label %for.body
for.end: ; preds = %for.body, %entry
%sum.0.lcssa = phi i3 [ 0, %entry ], [ %add, %for.body ]
ret i3 %sum.0.lcssa
}
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