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llvm-project/llvm/test/Transforms/LoopUnroll/runtime-small-upperbound.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

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; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt -S -passes=loop-unroll -unroll-runtime %s -o - | FileCheck %s
; RUN: opt -S -passes=loop-unroll -unroll-runtime -unroll-max-upperbound=6 %s -o - | FileCheck %s --check-prefix=UPPER
target datalayout = "e-m:e-p:32:32-i64:64-v128:64:128-a:0:32-n32-S64"
@global = dso_local local_unnamed_addr global i32 0, align 4
@global.1 = dso_local local_unnamed_addr global ptr null, align 4
; Check that loop in hoge_3, with a runtime upperbound of 3, is not unrolled.
define dso_local void @hoge_3(i8 %arg) {
; CHECK-LABEL: @hoge_3(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[X:%.*]] = load i32, ptr @global, align 4
; CHECK-NEXT: [[Y:%.*]] = load ptr, ptr @global.1, align 4
; CHECK-NEXT: [[TMP0:%.*]] = icmp ult i32 [[X]], 17
; CHECK-NEXT: br i1 [[TMP0]], label [[LOOP_PREHEADER:%.*]], label [[EXIT:%.*]]
; CHECK: loop.preheader:
; CHECK-NEXT: br label [[LOOP:%.*]]
; CHECK: loop:
; CHECK-NEXT: [[IV:%.*]] = phi i32 [ [[IV_NEXT:%.*]], [[LOOP]] ], [ [[X]], [[LOOP_PREHEADER]] ]
; CHECK-NEXT: [[PTR:%.*]] = phi ptr [ [[PTR_NEXT:%.*]], [[LOOP]] ], [ [[Y]], [[LOOP_PREHEADER]] ]
; CHECK-NEXT: [[IV_NEXT]] = add nuw i32 [[IV]], 8
; CHECK-NEXT: [[PTR_NEXT]] = getelementptr inbounds i8, ptr [[PTR]], i32 1
; CHECK-NEXT: store i8 [[ARG:%.*]], ptr [[PTR_NEXT]], align 1
; CHECK-NEXT: [[TMP1:%.*]] = icmp ult i32 [[IV_NEXT]], 17
; CHECK-NEXT: br i1 [[TMP1]], label [[LOOP]], label [[EXIT_LOOPEXIT:%.*]]
; CHECK: exit.loopexit:
; CHECK-NEXT: br label [[EXIT]]
; CHECK: exit:
; CHECK-NEXT: ret void
;
; UPPER-LABEL: @hoge_3(
; UPPER-NEXT: entry:
; UPPER-NEXT: [[X:%.*]] = load i32, ptr @global, align 4
; UPPER-NEXT: [[Y:%.*]] = load ptr, ptr @global.1, align 4
; UPPER-NEXT: [[TMP0:%.*]] = icmp ult i32 [[X]], 17
; UPPER-NEXT: br i1 [[TMP0]], label [[LOOP_PREHEADER:%.*]], label [[EXIT:%.*]]
; UPPER: loop.preheader:
; UPPER-NEXT: br label [[LOOP:%.*]]
; UPPER: loop:
; UPPER-NEXT: [[IV:%.*]] = phi i32 [ [[IV_NEXT:%.*]], [[LOOP]] ], [ [[X]], [[LOOP_PREHEADER]] ]
; UPPER-NEXT: [[PTR:%.*]] = phi ptr [ [[PTR_NEXT:%.*]], [[LOOP]] ], [ [[Y]], [[LOOP_PREHEADER]] ]
; UPPER-NEXT: [[IV_NEXT]] = add nuw i32 [[IV]], 8
; UPPER-NEXT: [[PTR_NEXT]] = getelementptr inbounds i8, ptr [[PTR]], i32 1
; UPPER-NEXT: store i8 [[ARG:%.*]], ptr [[PTR_NEXT]], align 1
; UPPER-NEXT: [[TMP1:%.*]] = icmp ult i32 [[IV_NEXT]], 17
; UPPER-NEXT: br i1 [[TMP1]], label [[LOOP]], label [[EXIT_LOOPEXIT:%.*]]
; UPPER: exit.loopexit:
; UPPER-NEXT: br label [[EXIT]]
; UPPER: exit:
; UPPER-NEXT: ret void
;
entry:
%x = load i32, ptr @global, align 4
%y = load ptr, ptr @global.1, align 4
%0 = icmp ult i32 %x, 17
br i1 %0, label %loop, label %exit
loop:
%iv = phi i32 [ %x, %entry ], [ %iv.next, %loop ]
%ptr = phi ptr [ %y, %entry ], [ %ptr.next, %loop ]
%iv.next = add nuw i32 %iv, 8
%ptr.next = getelementptr inbounds i8, ptr %ptr, i32 1
store i8 %arg, ptr %ptr.next, align 1
%1 = icmp ult i32 %iv.next, 17
br i1 %1, label %loop, label %exit
exit:
ret void
}
; Check that loop in hoge_5, with a runtime upperbound of 5, is unrolled when -unroll-max-upperbound=4
define dso_local void @hoge_5(i8 %arg) {
; CHECK-LABEL: @hoge_5(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[X:%.*]] = load i32, ptr @global, align 4
; CHECK-NEXT: [[Y:%.*]] = load ptr, ptr @global.1, align 4
; CHECK-NEXT: [[TMP0:%.*]] = icmp ult i32 [[X]], 17
; CHECK-NEXT: br i1 [[TMP0]], label [[LOOP_PREHEADER:%.*]], label [[EXIT:%.*]]
; CHECK: loop.preheader:
; CHECK-NEXT: br label [[LOOP:%.*]]
; CHECK: loop:
; CHECK-NEXT: [[IV:%.*]] = phi i32 [ [[IV_NEXT:%.*]], [[LOOP]] ], [ [[X]], [[LOOP_PREHEADER]] ]
; CHECK-NEXT: [[PTR:%.*]] = phi ptr [ [[PTR_NEXT:%.*]], [[LOOP]] ], [ [[Y]], [[LOOP_PREHEADER]] ]
; CHECK-NEXT: [[IV_NEXT]] = add nuw i32 [[IV]], 4
; CHECK-NEXT: [[PTR_NEXT]] = getelementptr inbounds i8, ptr [[PTR]], i32 1
; CHECK-NEXT: store i8 [[ARG:%.*]], ptr [[PTR_NEXT]], align 1
; CHECK-NEXT: [[TMP1:%.*]] = icmp ult i32 [[IV_NEXT]], 17
; CHECK-NEXT: br i1 [[TMP1]], label [[LOOP]], label [[EXIT_LOOPEXIT:%.*]]
; CHECK: exit.loopexit:
; CHECK-NEXT: br label [[EXIT]]
; CHECK: exit:
; CHECK-NEXT: ret void
;
; UPPER-LABEL: @hoge_5(
; UPPER-NEXT: entry:
; UPPER-NEXT: [[X:%.*]] = load i32, ptr @global, align 4
; UPPER-NEXT: [[Y:%.*]] = load ptr, ptr @global.1, align 4
; UPPER-NEXT: [[TMP0:%.*]] = icmp ult i32 [[X]], 17
; UPPER-NEXT: br i1 [[TMP0]], label [[LOOP_PREHEADER:%.*]], label [[EXIT:%.*]]
; UPPER: loop.preheader:
; UPPER-NEXT: br label [[LOOP:%.*]]
; UPPER: loop:
; UPPER-NEXT: [[IV_NEXT:%.*]] = add nuw i32 [[X]], 4
; UPPER-NEXT: [[PTR_NEXT:%.*]] = getelementptr inbounds i8, ptr [[Y]], i32 1
; UPPER-NEXT: store i8 [[ARG:%.*]], ptr [[PTR_NEXT]], align 1
; UPPER-NEXT: [[TMP1:%.*]] = icmp ult i32 [[IV_NEXT]], 17
; UPPER-NEXT: br i1 [[TMP1]], label [[LOOP_1:%.*]], label [[EXIT_LOOPEXIT:%.*]]
; UPPER: loop.1:
; UPPER-NEXT: [[IV_NEXT_1:%.*]] = add nuw i32 [[X]], 8
; UPPER-NEXT: [[PTR_NEXT_1:%.*]] = getelementptr inbounds i8, ptr [[PTR_NEXT]], i32 1
; UPPER-NEXT: store i8 [[ARG]], ptr [[PTR_NEXT_1]], align 1
; UPPER-NEXT: [[TMP2:%.*]] = icmp ult i32 [[IV_NEXT_1]], 17
; UPPER-NEXT: br i1 [[TMP2]], label [[LOOP_2:%.*]], label [[EXIT_LOOPEXIT]]
; UPPER: loop.2:
; UPPER-NEXT: [[IV_NEXT_2:%.*]] = add nuw i32 [[X]], 12
; UPPER-NEXT: [[PTR_NEXT_2:%.*]] = getelementptr inbounds i8, ptr [[PTR_NEXT_1]], i32 1
; UPPER-NEXT: store i8 [[ARG]], ptr [[PTR_NEXT_2]], align 1
; UPPER-NEXT: [[TMP3:%.*]] = icmp ult i32 [[IV_NEXT_2]], 17
; UPPER-NEXT: br i1 [[TMP3]], label [[LOOP_3:%.*]], label [[EXIT_LOOPEXIT]]
; UPPER: loop.3:
; UPPER-NEXT: [[IV_NEXT_3:%.*]] = add nuw i32 [[X]], 16
; UPPER-NEXT: [[PTR_NEXT_3:%.*]] = getelementptr inbounds i8, ptr [[PTR_NEXT_2]], i32 1
; UPPER-NEXT: store i8 [[ARG]], ptr [[PTR_NEXT_3]], align 1
; UPPER-NEXT: [[TMP4:%.*]] = icmp ult i32 [[IV_NEXT_3]], 17
; UPPER-NEXT: br i1 [[TMP4]], label [[LOOP_4:%.*]], label [[EXIT_LOOPEXIT]]
; UPPER: loop.4:
; UPPER-NEXT: [[PTR_NEXT_4:%.*]] = getelementptr inbounds i8, ptr [[PTR_NEXT_3]], i32 1
; UPPER-NEXT: store i8 [[ARG]], ptr [[PTR_NEXT_4]], align 1
; UPPER-NEXT: br i1 false, label [[LOOP_5:%.*]], label [[EXIT_LOOPEXIT]]
; UPPER: loop.5:
; UPPER-NEXT: [[PTR_NEXT_5:%.*]] = getelementptr inbounds i8, ptr [[PTR_NEXT_4]], i32 1
; UPPER-NEXT: store i8 [[ARG]], ptr [[PTR_NEXT_5]], align 1
; UPPER-NEXT: br label [[EXIT_LOOPEXIT]]
; UPPER: exit.loopexit:
; UPPER-NEXT: br label [[EXIT]]
; UPPER: exit:
; UPPER-NEXT: ret void
;
entry:
%x = load i32, ptr @global, align 4
%y = load ptr, ptr @global.1, align 4
%0 = icmp ult i32 %x, 17
br i1 %0, label %loop, label %exit
loop:
%iv = phi i32 [ %x, %entry ], [ %iv.next, %loop ]
%ptr = phi ptr [ %y, %entry ], [ %ptr.next, %loop ]
%iv.next = add nuw i32 %iv, 4
%ptr.next = getelementptr inbounds i8, ptr %ptr, i32 1
store i8 %arg, ptr %ptr.next, align 1
%1 = icmp ult i32 %iv.next, 17
br i1 %1, label %loop, label %exit
exit:
ret void
}
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