de2fed6152
The unrolling code was previously inserting new cloned blocks at the end of the function. The result of this with typical loop structures is that the new iterations are placed far from the initial iteration. With unrolling, the general assumption is that the a) the loop is reasonable hot, and b) the first Count-1 copies of the loop are rarely (if ever) loop exiting. As such, placing Count-1 copies out of line is a fairly poor code placement choice. We'd much rather fall through into the hot (non-exiting) path. For code with branch profiles, later layout would fix this, but this may have a positive impact on non-PGO compiled code. However, the real motivation for this change isn't performance. Its readability and human understanding. Having to jump around long distances in an IR file to trace an unrolled loop structure is error prone and tedious.
87 lines
3.8 KiB
LLVM
87 lines
3.8 KiB
LLVM
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
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; RUN: opt -loop-unroll -S %s | FileCheck %s
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; Loop with multiple exiting blocks, where the header exits but not the latch,
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; e.g. because it has not been rotated.
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define i16 @full_unroll_multiple_exiting_blocks(i16* %A, i16 %x, i16 %y) {
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; CHECK-LABEL: @full_unroll_multiple_exiting_blocks(
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; CHECK-NEXT: entry:
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; CHECK-NEXT: br label [[HEADER:%.*]]
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; CHECK: header:
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; CHECK-NEXT: [[LV:%.*]] = load i16, i16* [[A:%.*]], align 2
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; CHECK-NEXT: [[RES_NEXT:%.*]] = add i16 123, [[LV]]
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; CHECK-NEXT: br label [[EXITING_1:%.*]]
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; CHECK: exiting.1:
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; CHECK-NEXT: [[EC_1:%.*]] = icmp eq i16 [[LV]], [[X:%.*]]
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; CHECK-NEXT: br i1 [[EC_1]], label [[EXIT:%.*]], label [[EXITING_2:%.*]]
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; CHECK: exiting.2:
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; CHECK-NEXT: [[EC_2:%.*]] = icmp eq i16 [[LV]], [[Y:%.*]]
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; CHECK-NEXT: br i1 [[EC_2]], label [[EXIT]], label [[LATCH:%.*]]
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; CHECK: latch:
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; CHECK-NEXT: [[PTR_1:%.*]] = getelementptr inbounds i16, i16* [[A]], i64 1
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; CHECK-NEXT: [[LV_1:%.*]] = load i16, i16* [[PTR_1]], align 2
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; CHECK-NEXT: [[RES_NEXT_1:%.*]] = add i16 [[RES_NEXT]], [[LV_1]]
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; CHECK-NEXT: br label [[EXITING_1_1:%.*]]
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; CHECK: exiting.1.1:
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; CHECK-NEXT: [[EC_1_1:%.*]] = icmp eq i16 [[LV_1]], [[X]]
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; CHECK-NEXT: br i1 [[EC_1_1]], label [[EXIT]], label [[EXITING_2_1:%.*]]
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; CHECK: exiting.2.1:
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; CHECK-NEXT: [[EC_2_1:%.*]] = icmp eq i16 [[LV_1]], [[Y]]
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; CHECK-NEXT: br i1 [[EC_2_1]], label [[EXIT]], label [[LATCH_1:%.*]]
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; CHECK: latch.1:
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; CHECK-NEXT: [[PTR_2:%.*]] = getelementptr inbounds i16, i16* [[A]], i64 2
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; CHECK-NEXT: [[LV_2:%.*]] = load i16, i16* [[PTR_2]], align 2
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; CHECK-NEXT: [[RES_NEXT_2:%.*]] = add i16 [[RES_NEXT_1]], [[LV_2]]
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; CHECK-NEXT: br label [[EXITING_1_2:%.*]]
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; CHECK: exiting.1.2:
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; CHECK-NEXT: [[EC_1_2:%.*]] = icmp eq i16 [[LV_2]], [[X]]
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; CHECK-NEXT: br i1 [[EC_1_2]], label [[EXIT]], label [[EXITING_2_2:%.*]]
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; CHECK: exiting.2.2:
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; CHECK-NEXT: [[EC_2_2:%.*]] = icmp eq i16 [[LV_2]], [[Y]]
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; CHECK-NEXT: br i1 [[EC_2_2]], label [[EXIT]], label [[LATCH_2:%.*]]
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; CHECK: latch.2:
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; CHECK-NEXT: [[PTR_3:%.*]] = getelementptr inbounds i16, i16* [[A]], i64 3
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; CHECK-NEXT: [[LV_3:%.*]] = load i16, i16* [[PTR_3]], align 2
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; CHECK-NEXT: [[RES_NEXT_3:%.*]] = add i16 [[RES_NEXT_2]], [[LV_3]]
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; CHECK-NEXT: br i1 false, label [[EXITING_1_3:%.*]], label [[EXIT]]
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; CHECK: exiting.1.3:
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; CHECK-NEXT: [[EC_1_3:%.*]] = icmp eq i16 [[LV_3]], [[X]]
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; CHECK-NEXT: br i1 [[EC_1_3]], label [[EXIT]], label [[EXITING_2_3:%.*]]
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; CHECK: exiting.2.3:
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; CHECK-NEXT: [[EC_2_3:%.*]] = icmp eq i16 [[LV_3]], [[Y]]
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; CHECK-NEXT: br i1 [[EC_2_3]], label [[EXIT]], label [[LATCH_3:%.*]]
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; CHECK: latch.3:
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; CHECK-NEXT: unreachable
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; CHECK: exit:
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; CHECK-NEXT: [[RES_LCSSA:%.*]] = phi i16 [ 0, [[EXITING_1]] ], [ 1, [[EXITING_2]] ], [ 0, [[EXITING_1_1]] ], [ 1, [[EXITING_2_1]] ], [ 0, [[EXITING_1_2]] ], [ 1, [[EXITING_2_2]] ], [ [[RES_NEXT_3]], [[LATCH_2]] ], [ 0, [[EXITING_1_3]] ], [ 1, [[EXITING_2_3]] ]
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; CHECK-NEXT: ret i16 [[RES_LCSSA]]
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;
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entry:
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br label %header
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header:
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%res = phi i16 [ 123, %entry ], [ %res.next, %latch ]
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%i.0 = phi i64 [ 0, %entry ], [ %inc9, %latch ]
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%ptr = getelementptr inbounds i16, i16* %A, i64 %i.0
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%lv = load i16, i16* %ptr
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%res.next = add i16 %res, %lv
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%cmp = icmp ult i64 %i.0, 3
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br i1 %cmp, label %exiting.1, label %exit
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exiting.1:
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%ec.1 = icmp eq i16 %lv, %x
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br i1 %ec.1, label %exit, label %exiting.2
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exiting.2:
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%ec.2 = icmp eq i16 %lv, %y
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br i1 %ec.2, label %exit, label %latch
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latch:
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%inc9 = add i64 %i.0, 1
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br label %header
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exit:
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%res.lcssa = phi i16 [ %res.next, %header ], [ 0, %exiting.1 ], [ 1, %exiting.2 ]
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ret i16 %res.lcssa
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}
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