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clang-p2996/llvm/test/Transforms/LoopUnroll/runtime-loop-at-most-two-exits.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

166 lines
11 KiB
LLVM
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; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt < %s -passes=loop-unroll -unroll-runtime=true -unroll-runtime-epilog=true -unroll-runtime-other-exit-predictable=true -verify-loop-lcssa -verify-dom-info -verify-loop-info -S | FileCheck %s --check-prefix=ENABLED
; RUN: opt < %s -passes=loop-unroll -unroll-runtime=true -unroll-runtime-epilog=true -unroll-runtime-other-exit-predictable=false -verify-loop-lcssa -verify-dom-info -verify-loop-info -S | FileCheck %s --check-prefix=DISABLED
define i32 @test(ptr nocapture %a, i64 %n) {
; ENABLED-LABEL: @test(
; ENABLED-NEXT: entry:
; ENABLED-NEXT: [[TMP0:%.*]] = freeze i64 [[N:%.*]]
; ENABLED-NEXT: [[TMP1:%.*]] = add i64 [[TMP0]], -1
; ENABLED-NEXT: [[XTRAITER:%.*]] = and i64 [[TMP0]], 7
; ENABLED-NEXT: [[TMP2:%.*]] = icmp ult i64 [[TMP1]], 7
; ENABLED-NEXT: br i1 [[TMP2]], label [[FOR_END_UNR_LCSSA:%.*]], label [[ENTRY_NEW:%.*]]
; ENABLED: entry.new:
; ENABLED-NEXT: [[UNROLL_ITER:%.*]] = sub i64 [[TMP0]], [[XTRAITER]]
; ENABLED-NEXT: br label [[HEADER:%.*]]
; ENABLED: header:
; ENABLED-NEXT: [[INDVARS_IV:%.*]] = phi i64 [ 0, [[ENTRY_NEW]] ], [ [[INDVARS_IV_NEXT_7:%.*]], [[FOR_BODY_7:%.*]] ]
; ENABLED-NEXT: [[SUM_02:%.*]] = phi i32 [ 0, [[ENTRY_NEW]] ], [ [[ADD_7:%.*]], [[FOR_BODY_7]] ]
; ENABLED-NEXT: [[NITER:%.*]] = phi i64 [ 0, [[ENTRY_NEW]] ], [ [[NITER_NEXT_7:%.*]], [[FOR_BODY_7]] ]
; ENABLED-NEXT: [[CMP:%.*]] = icmp eq i64 [[N]], 42
; ENABLED-NEXT: br i1 [[CMP]], label [[FOR_EXIT2_LOOPEXIT:%.*]], label [[FOR_BODY:%.*]]
; ENABLED: for.body:
; ENABLED-NEXT: [[ARRAYIDX:%.*]] = getelementptr inbounds i32, ptr [[A:%.*]], i64 [[INDVARS_IV]]
; ENABLED-NEXT: [[TMP3:%.*]] = load i32, ptr [[ARRAYIDX]], align 4
; ENABLED-NEXT: [[ADD:%.*]] = add nsw i32 [[TMP3]], [[SUM_02]]
; ENABLED-NEXT: [[INDVARS_IV_NEXT:%.*]] = add nuw nsw i64 [[INDVARS_IV]], 1
; ENABLED-NEXT: br i1 false, label [[FOR_EXIT2_LOOPEXIT]], label [[FOR_BODY_1:%.*]]
; ENABLED: for.body.1:
; ENABLED-NEXT: [[ARRAYIDX_1:%.*]] = getelementptr inbounds i32, ptr [[A]], i64 [[INDVARS_IV_NEXT]]
; ENABLED-NEXT: [[TMP4:%.*]] = load i32, ptr [[ARRAYIDX_1]], align 4
; ENABLED-NEXT: [[ADD_1:%.*]] = add nsw i32 [[TMP4]], [[ADD]]
; ENABLED-NEXT: [[INDVARS_IV_NEXT_1:%.*]] = add nuw nsw i64 [[INDVARS_IV]], 2
; ENABLED-NEXT: [[CMP_2:%.*]] = icmp eq i64 [[N]], 42
; ENABLED-NEXT: br i1 [[CMP_2]], label [[FOR_EXIT2_LOOPEXIT]], label [[FOR_BODY_2:%.*]]
; ENABLED: for.body.2:
; ENABLED-NEXT: [[ARRAYIDX_2:%.*]] = getelementptr inbounds i32, ptr [[A]], i64 [[INDVARS_IV_NEXT_1]]
; ENABLED-NEXT: [[TMP5:%.*]] = load i32, ptr [[ARRAYIDX_2]], align 4
; ENABLED-NEXT: [[ADD_2:%.*]] = add nsw i32 [[TMP5]], [[ADD_1]]
; ENABLED-NEXT: [[INDVARS_IV_NEXT_2:%.*]] = add nuw nsw i64 [[INDVARS_IV]], 3
; ENABLED-NEXT: br i1 false, label [[FOR_EXIT2_LOOPEXIT]], label [[FOR_BODY_3:%.*]]
; ENABLED: for.body.3:
; ENABLED-NEXT: [[ARRAYIDX_3:%.*]] = getelementptr inbounds i32, ptr [[A]], i64 [[INDVARS_IV_NEXT_2]]
; ENABLED-NEXT: [[TMP6:%.*]] = load i32, ptr [[ARRAYIDX_3]], align 4
; ENABLED-NEXT: [[ADD_3:%.*]] = add nsw i32 [[TMP6]], [[ADD_2]]
; ENABLED-NEXT: [[INDVARS_IV_NEXT_3:%.*]] = add nuw nsw i64 [[INDVARS_IV]], 4
; ENABLED-NEXT: [[CMP_4:%.*]] = icmp eq i64 [[N]], 42
; ENABLED-NEXT: br i1 [[CMP_4]], label [[FOR_EXIT2_LOOPEXIT]], label [[FOR_BODY_4:%.*]]
; ENABLED: for.body.4:
; ENABLED-NEXT: [[ARRAYIDX_4:%.*]] = getelementptr inbounds i32, ptr [[A]], i64 [[INDVARS_IV_NEXT_3]]
; ENABLED-NEXT: [[TMP7:%.*]] = load i32, ptr [[ARRAYIDX_4]], align 4
; ENABLED-NEXT: [[ADD_4:%.*]] = add nsw i32 [[TMP7]], [[ADD_3]]
; ENABLED-NEXT: [[INDVARS_IV_NEXT_4:%.*]] = add nuw nsw i64 [[INDVARS_IV]], 5
; ENABLED-NEXT: br i1 false, label [[FOR_EXIT2_LOOPEXIT]], label [[FOR_BODY_5:%.*]]
; ENABLED: for.body.5:
; ENABLED-NEXT: [[ARRAYIDX_5:%.*]] = getelementptr inbounds i32, ptr [[A]], i64 [[INDVARS_IV_NEXT_4]]
; ENABLED-NEXT: [[TMP8:%.*]] = load i32, ptr [[ARRAYIDX_5]], align 4
; ENABLED-NEXT: [[ADD_5:%.*]] = add nsw i32 [[TMP8]], [[ADD_4]]
; ENABLED-NEXT: [[INDVARS_IV_NEXT_5:%.*]] = add nuw nsw i64 [[INDVARS_IV]], 6
; ENABLED-NEXT: [[CMP_6:%.*]] = icmp eq i64 [[N]], 42
; ENABLED-NEXT: br i1 [[CMP_6]], label [[FOR_EXIT2_LOOPEXIT]], label [[FOR_BODY_6:%.*]]
; ENABLED: for.body.6:
; ENABLED-NEXT: [[ARRAYIDX_6:%.*]] = getelementptr inbounds i32, ptr [[A]], i64 [[INDVARS_IV_NEXT_5]]
; ENABLED-NEXT: [[TMP9:%.*]] = load i32, ptr [[ARRAYIDX_6]], align 4
; ENABLED-NEXT: [[ADD_6:%.*]] = add nsw i32 [[TMP9]], [[ADD_5]]
; ENABLED-NEXT: [[INDVARS_IV_NEXT_6:%.*]] = add nuw nsw i64 [[INDVARS_IV]], 7
; ENABLED-NEXT: br i1 false, label [[FOR_EXIT2_LOOPEXIT]], label [[FOR_BODY_7]]
; ENABLED: for.body.7:
; ENABLED-NEXT: [[ARRAYIDX_7:%.*]] = getelementptr inbounds i32, ptr [[A]], i64 [[INDVARS_IV_NEXT_6]]
; ENABLED-NEXT: [[TMP10:%.*]] = load i32, ptr [[ARRAYIDX_7]], align 4
; ENABLED-NEXT: [[ADD_7]] = add nsw i32 [[TMP10]], [[ADD_6]]
; ENABLED-NEXT: [[INDVARS_IV_NEXT_7]] = add i64 [[INDVARS_IV]], 8
; ENABLED-NEXT: [[NITER_NEXT_7]] = add i64 [[NITER]], 8
; ENABLED-NEXT: [[NITER_NCMP_7:%.*]] = icmp eq i64 [[NITER_NEXT_7]], [[UNROLL_ITER]]
; ENABLED-NEXT: br i1 [[NITER_NCMP_7]], label [[FOR_END_UNR_LCSSA_LOOPEXIT:%.*]], label [[HEADER]]
; ENABLED: for.end.unr-lcssa.loopexit:
; ENABLED-NEXT: [[SUM_0_LCSSA_PH_PH:%.*]] = phi i32 [ [[ADD_7]], [[FOR_BODY_7]] ]
; ENABLED-NEXT: [[INDVARS_IV_UNR_PH:%.*]] = phi i64 [ [[INDVARS_IV_NEXT_7]], [[FOR_BODY_7]] ]
; ENABLED-NEXT: [[SUM_02_UNR_PH:%.*]] = phi i32 [ [[ADD_7]], [[FOR_BODY_7]] ]
; ENABLED-NEXT: br label [[FOR_END_UNR_LCSSA]]
; ENABLED: for.end.unr-lcssa:
; ENABLED-NEXT: [[SUM_0_LCSSA_PH:%.*]] = phi i32 [ undef, [[ENTRY:%.*]] ], [ [[SUM_0_LCSSA_PH_PH]], [[FOR_END_UNR_LCSSA_LOOPEXIT]] ]
; ENABLED-NEXT: [[INDVARS_IV_UNR:%.*]] = phi i64 [ 0, [[ENTRY]] ], [ [[INDVARS_IV_UNR_PH]], [[FOR_END_UNR_LCSSA_LOOPEXIT]] ]
; ENABLED-NEXT: [[SUM_02_UNR:%.*]] = phi i32 [ 0, [[ENTRY]] ], [ [[SUM_02_UNR_PH]], [[FOR_END_UNR_LCSSA_LOOPEXIT]] ]
; ENABLED-NEXT: [[LCMP_MOD:%.*]] = icmp ne i64 [[XTRAITER]], 0
; ENABLED-NEXT: br i1 [[LCMP_MOD]], label [[HEADER_EPIL_PREHEADER:%.*]], label [[FOR_END:%.*]]
; ENABLED: header.epil.preheader:
; ENABLED-NEXT: br label [[HEADER_EPIL:%.*]]
; ENABLED: header.epil:
; ENABLED-NEXT: [[INDVARS_IV_EPIL:%.*]] = phi i64 [ [[INDVARS_IV_NEXT_EPIL:%.*]], [[FOR_BODY_EPIL:%.*]] ], [ [[INDVARS_IV_UNR]], [[HEADER_EPIL_PREHEADER]] ]
; ENABLED-NEXT: [[SUM_02_EPIL:%.*]] = phi i32 [ [[ADD_EPIL:%.*]], [[FOR_BODY_EPIL]] ], [ [[SUM_02_UNR]], [[HEADER_EPIL_PREHEADER]] ]
; ENABLED-NEXT: [[EPIL_ITER:%.*]] = phi i64 [ 0, [[HEADER_EPIL_PREHEADER]] ], [ [[EPIL_ITER_NEXT:%.*]], [[FOR_BODY_EPIL]] ]
; ENABLED-NEXT: [[CMP_EPIL:%.*]] = icmp eq i64 [[N]], 42
; ENABLED-NEXT: br i1 [[CMP_EPIL]], label [[FOR_EXIT2_LOOPEXIT2:%.*]], label [[FOR_BODY_EPIL]]
; ENABLED: for.body.epil:
; ENABLED-NEXT: [[ARRAYIDX_EPIL:%.*]] = getelementptr inbounds i32, ptr [[A]], i64 [[INDVARS_IV_EPIL]]
; ENABLED-NEXT: [[TMP11:%.*]] = load i32, ptr [[ARRAYIDX_EPIL]], align 4
; ENABLED-NEXT: [[ADD_EPIL]] = add nsw i32 [[TMP11]], [[SUM_02_EPIL]]
; ENABLED-NEXT: [[INDVARS_IV_NEXT_EPIL]] = add i64 [[INDVARS_IV_EPIL]], 1
; ENABLED-NEXT: [[EXITCOND_EPIL:%.*]] = icmp eq i64 [[INDVARS_IV_NEXT_EPIL]], [[N]]
; ENABLED-NEXT: [[EPIL_ITER_NEXT]] = add i64 [[EPIL_ITER]], 1
; ENABLED-NEXT: [[EPIL_ITER_CMP:%.*]] = icmp ne i64 [[EPIL_ITER_NEXT]], [[XTRAITER]]
; ENABLED-NEXT: br i1 [[EPIL_ITER_CMP]], label [[HEADER_EPIL]], label [[FOR_END_EPILOG_LCSSA:%.*]], !llvm.loop [[LOOP0:![0-9]+]]
; ENABLED: for.end.epilog-lcssa:
; ENABLED-NEXT: [[SUM_0_LCSSA_PH1:%.*]] = phi i32 [ [[ADD_EPIL]], [[FOR_BODY_EPIL]] ]
; ENABLED-NEXT: br label [[FOR_END]]
; ENABLED: for.end:
; ENABLED-NEXT: [[SUM_0_LCSSA:%.*]] = phi i32 [ [[SUM_0_LCSSA_PH]], [[FOR_END_UNR_LCSSA]] ], [ [[SUM_0_LCSSA_PH1]], [[FOR_END_EPILOG_LCSSA]] ]
; ENABLED-NEXT: ret i32 [[SUM_0_LCSSA]]
; ENABLED: for.exit2.loopexit:
; ENABLED-NEXT: [[RETVAL_PH:%.*]] = phi i32 [ [[SUM_02]], [[HEADER]] ], [ [[ADD]], [[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]] ]
; ENABLED-NEXT: br label [[FOR_EXIT2:%.*]]
; ENABLED: for.exit2.loopexit2:
; ENABLED-NEXT: [[RETVAL_PH3:%.*]] = phi i32 [ [[SUM_02_EPIL]], [[HEADER_EPIL]] ]
; ENABLED-NEXT: br label [[FOR_EXIT2]]
; ENABLED: for.exit2:
; ENABLED-NEXT: [[RETVAL:%.*]] = phi i32 [ [[RETVAL_PH]], [[FOR_EXIT2_LOOPEXIT]] ], [ [[RETVAL_PH3]], [[FOR_EXIT2_LOOPEXIT2]] ]
; ENABLED-NEXT: ret i32 [[RETVAL]]
;
; DISABLED-LABEL: @test(
; DISABLED-NEXT: entry:
; DISABLED-NEXT: br label [[HEADER:%.*]]
; DISABLED: header:
; DISABLED-NEXT: [[INDVARS_IV:%.*]] = phi i64 [ [[INDVARS_IV_NEXT:%.*]], [[FOR_BODY:%.*]] ], [ 0, [[ENTRY:%.*]] ]
; DISABLED-NEXT: [[SUM_02:%.*]] = phi i32 [ [[ADD:%.*]], [[FOR_BODY]] ], [ 0, [[ENTRY]] ]
; DISABLED-NEXT: [[CMP:%.*]] = icmp eq i64 [[N:%.*]], 42
; DISABLED-NEXT: br i1 [[CMP]], label [[FOR_EXIT2:%.*]], label [[FOR_BODY]]
; DISABLED: for.body:
; DISABLED-NEXT: [[ARRAYIDX:%.*]] = getelementptr inbounds i32, ptr [[A:%.*]], i64 [[INDVARS_IV]]
; DISABLED-NEXT: [[TMP0:%.*]] = load i32, ptr [[ARRAYIDX]], align 4
; DISABLED-NEXT: [[ADD]] = add nsw i32 [[TMP0]], [[SUM_02]]
; DISABLED-NEXT: [[INDVARS_IV_NEXT]] = add i64 [[INDVARS_IV]], 1
; DISABLED-NEXT: [[EXITCOND:%.*]] = icmp eq i64 [[INDVARS_IV_NEXT]], [[N]]
; DISABLED-NEXT: br i1 [[EXITCOND]], label [[FOR_END:%.*]], label [[HEADER]]
; DISABLED: for.end:
; DISABLED-NEXT: [[SUM_0_LCSSA:%.*]] = phi i32 [ [[ADD]], [[FOR_BODY]] ]
; DISABLED-NEXT: ret i32 [[SUM_0_LCSSA]]
; DISABLED: for.exit2:
; DISABLED-NEXT: [[RETVAL:%.*]] = phi i32 [ [[SUM_02]], [[HEADER]] ]
; DISABLED-NEXT: ret i32 [[RETVAL]]
;
entry:
br label %header
header:
%indvars.iv = phi i64 [ %indvars.iv.next, %for.body ], [ 0, %entry ]
%sum.02 = phi i32 [ %add, %for.body ], [ 0, %entry ]
%cmp = icmp eq i64 %n, 42
br i1 %cmp, label %for.exit2, label %for.body
for.body:
%arrayidx = getelementptr inbounds i32, ptr %a, i64 %indvars.iv
%0 = load i32, ptr %arrayidx, align 4
%add = add nsw i32 %0, %sum.02
%indvars.iv.next = add i64 %indvars.iv, 1
%exitcond = icmp eq i64 %indvars.iv.next, %n
br i1 %exitcond, label %for.end, label %header
for.end:
%sum.0.lcssa = phi i32 [ %add, %for.body ]
ret i32 %sum.0.lcssa
for.exit2:
%retval = phi i32 [ %sum.02, %header ]
ret i32 %retval
}
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