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clang-p2996/llvm/test/Transforms/LoopUnroll/nonlatchcondbr.ll
Philip Reames de2fed6152 [unroll] Keep unrolled iterations with initial iteration 
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.
2021-11-12 11:40:50 -08:00

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; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt < %s -loop-unroll -unroll-runtime -unroll-count=4 -S | FileCheck %s
; RUN: opt < %s -passes='require<opt-remark-emit>,loop-unroll' -unroll-runtime -unroll-count=4 -S | FileCheck %s
; Check that loop unroll pass correctly handle loops with
; single exiting block not the loop header or latch.
define void @test1(i32* noalias %A) {
; CHECK-LABEL: @test1(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[TMP0:%.*]] = load i32, i32* [[A:%.*]], align 4
; CHECK-NEXT: call void @bar(i32 [[TMP0]])
; CHECK-NEXT: br label [[FOR_HEADER:%.*]]
; CHECK: for.header:
; CHECK-NEXT: call void @bar(i32 [[TMP0]])
; CHECK-NEXT: br label [[FOR_BODY:%.*]]
; CHECK: for.body:
; CHECK-NEXT: br label [[FOR_BODY_FOR_BODY_CRIT_EDGE:%.*]]
; CHECK: for.body.for.body_crit_edge:
; CHECK-NEXT: [[ARRAYIDX_PHI_TRANS_INSERT:%.*]] = getelementptr inbounds i32, i32* [[A]], i64 1
; CHECK-NEXT: [[DOTPRE:%.*]] = load i32, i32* [[ARRAYIDX_PHI_TRANS_INSERT]], align 4
; CHECK-NEXT: call void @bar(i32 [[DOTPRE]])
; CHECK-NEXT: br label [[FOR_BODY_1:%.*]]
; CHECK: for.body.1:
; CHECK-NEXT: br label [[FOR_BODY_FOR_BODY_CRIT_EDGE_1:%.*]]
; CHECK: for.body.for.body_crit_edge.1:
; CHECK-NEXT: [[ARRAYIDX_PHI_TRANS_INSERT_1:%.*]] = getelementptr inbounds i32, i32* [[A]], i64 2
; CHECK-NEXT: [[DOTPRE_1:%.*]] = load i32, i32* [[ARRAYIDX_PHI_TRANS_INSERT_1]], align 4
; CHECK-NEXT: call void @bar(i32 [[DOTPRE_1]])
; CHECK-NEXT: br label [[FOR_BODY_2:%.*]]
; CHECK: for.body.2:
; CHECK-NEXT: br label [[FOR_BODY_FOR_BODY_CRIT_EDGE_2:%.*]]
; CHECK: for.body.for.body_crit_edge.2:
; CHECK-NEXT: [[ARRAYIDX_PHI_TRANS_INSERT_2:%.*]] = getelementptr inbounds i32, i32* [[A]], i64 3
; CHECK-NEXT: [[DOTPRE_2:%.*]] = load i32, i32* [[ARRAYIDX_PHI_TRANS_INSERT_2]], align 4
; CHECK-NEXT: call void @bar(i32 [[DOTPRE_2]])
; CHECK-NEXT: br label [[FOR_BODY_3:%.*]]
; CHECK: for.body.3:
; CHECK-NEXT: br i1 false, label [[FOR_BODY_FOR_BODY_CRIT_EDGE_3:%.*]], label [[FOR_END:%.*]]
; CHECK: for.body.for.body_crit_edge.3:
; CHECK-NEXT: unreachable
; CHECK: for.end:
; CHECK-NEXT: ret void
;
entry:
%0 = load i32, i32* %A, align 4
call void @bar(i32 %0)
br label %for.header
for.header:
%1 = phi i32 [ %0, %entry ], [ %.pre, %for.body.for.body_crit_edge ]
%i = phi i64 [ 0, %entry ], [ %inc, %for.body.for.body_crit_edge ]
%arrayidx = getelementptr inbounds i32, i32* %A, i64 %i
call void @bar(i32 %1)
br label %for.body
for.body:
%inc = add nsw i64 %i, 1
%cmp = icmp slt i64 %inc, 4
br i1 %cmp, label %for.body.for.body_crit_edge, label %for.end
for.body.for.body_crit_edge:
%arrayidx.phi.trans.insert = getelementptr inbounds i32, i32* %A, i64 %inc
%.pre = load i32, i32* %arrayidx.phi.trans.insert, align 4
br label %for.header
for.end:
ret void
}
; Check that loop unroll pass correctly handle loops with
; (1) exiting block not dominating the loop latch; and
; (2) exiting terminator instructions cannot be simplified to unconditional.
define void @test2(i32* noalias %A) {
; CHECK-LABEL: @test2(
; CHECK-NEXT: entry:
; CHECK-NEXT: br i1 true, label [[FOR_PREHEADER:%.*]], label [[FOR_END:%.*]]
; CHECK: for.preheader:
; CHECK-NEXT: [[TMP0:%.*]] = load i32, i32* [[A:%.*]], align 4
; CHECK-NEXT: call void @bar(i32 [[TMP0]])
; CHECK-NEXT: br label [[FOR_HEADER:%.*]]
; CHECK: for.header:
; CHECK-NEXT: [[TMP1:%.*]] = phi i32 [ [[TMP0]], [[FOR_PREHEADER]] ], [ [[DOTPRE_3:%.*]], [[FOR_BODY_FOR_BODY_CRIT_EDGE_3:%.*]] ]
; CHECK-NEXT: [[I:%.*]] = phi i64 [ 0, [[FOR_PREHEADER]] ], [ [[INC_3:%.*]], [[FOR_BODY_FOR_BODY_CRIT_EDGE_3]] ]
; CHECK-NEXT: call void @bar(i32 [[TMP1]])
; CHECK-NEXT: [[INC:%.*]] = add nuw nsw i64 [[I]], 1
; CHECK-NEXT: br i1 true, label [[FOR_BODY:%.*]], label [[FOR_BODY_FOR_BODY_CRIT_EDGE:%.*]]
; CHECK: for.body:
; CHECK-NEXT: [[CMP:%.*]] = call i1 @foo(i64 [[I]])
; CHECK-NEXT: br i1 [[CMP]], label [[FOR_BODY_FOR_BODY_CRIT_EDGE]], label [[FOR_END_LOOPEXIT:%.*]]
; CHECK: for.body.for.body_crit_edge:
; CHECK-NEXT: [[ARRAYIDX_PHI_TRANS_INSERT:%.*]] = getelementptr inbounds i32, i32* [[A]], i64 [[INC]]
; CHECK-NEXT: [[DOTPRE:%.*]] = load i32, i32* [[ARRAYIDX_PHI_TRANS_INSERT]], align 4
; CHECK-NEXT: call void @bar(i32 [[DOTPRE]])
; CHECK-NEXT: [[INC_1:%.*]] = add nuw nsw i64 [[INC]], 1
; CHECK-NEXT: br i1 true, label [[FOR_BODY_1:%.*]], label [[FOR_BODY_FOR_BODY_CRIT_EDGE_1:%.*]]
; CHECK: for.body.1:
; CHECK-NEXT: [[CMP_1:%.*]] = call i1 @foo(i64 [[INC]])
; CHECK-NEXT: br i1 [[CMP_1]], label [[FOR_BODY_FOR_BODY_CRIT_EDGE_1]], label [[FOR_END_LOOPEXIT]]
; CHECK: for.body.for.body_crit_edge.1:
; CHECK-NEXT: [[ARRAYIDX_PHI_TRANS_INSERT_1:%.*]] = getelementptr inbounds i32, i32* [[A]], i64 [[INC_1]]
; CHECK-NEXT: [[DOTPRE_1:%.*]] = load i32, i32* [[ARRAYIDX_PHI_TRANS_INSERT_1]], align 4
; CHECK-NEXT: call void @bar(i32 [[DOTPRE_1]])
; CHECK-NEXT: [[INC_2:%.*]] = add nuw nsw i64 [[INC_1]], 1
; CHECK-NEXT: br i1 true, label [[FOR_BODY_2:%.*]], label [[FOR_BODY_FOR_BODY_CRIT_EDGE_2:%.*]]
; CHECK: for.body.2:
; CHECK-NEXT: [[CMP_2:%.*]] = call i1 @foo(i64 [[INC_1]])
; CHECK-NEXT: br i1 [[CMP_2]], label [[FOR_BODY_FOR_BODY_CRIT_EDGE_2]], label [[FOR_END_LOOPEXIT]]
; CHECK: for.body.for.body_crit_edge.2:
; CHECK-NEXT: [[ARRAYIDX_PHI_TRANS_INSERT_2:%.*]] = getelementptr inbounds i32, i32* [[A]], i64 [[INC_2]]
; CHECK-NEXT: [[DOTPRE_2:%.*]] = load i32, i32* [[ARRAYIDX_PHI_TRANS_INSERT_2]], align 4
; CHECK-NEXT: call void @bar(i32 [[DOTPRE_2]])
; CHECK-NEXT: [[INC_3]] = add nsw i64 [[INC_2]], 1
; CHECK-NEXT: br i1 true, label [[FOR_BODY_3:%.*]], label [[FOR_BODY_FOR_BODY_CRIT_EDGE_3]]
; CHECK: for.body.3:
; CHECK-NEXT: [[CMP_3:%.*]] = call i1 @foo(i64 [[INC_2]])
; CHECK-NEXT: br i1 [[CMP_3]], label [[FOR_BODY_FOR_BODY_CRIT_EDGE_3]], label [[FOR_END_LOOPEXIT]]
; CHECK: for.body.for.body_crit_edge.3:
; CHECK-NEXT: [[ARRAYIDX_PHI_TRANS_INSERT_3:%.*]] = getelementptr inbounds i32, i32* [[A]], i64 [[INC_3]]
; CHECK-NEXT: [[DOTPRE_3]] = load i32, i32* [[ARRAYIDX_PHI_TRANS_INSERT_3]], align 4
; CHECK-NEXT: br label [[FOR_HEADER]], !llvm.loop [[LOOP0:![0-9]+]]
; CHECK: for.end.loopexit:
; CHECK-NEXT: br label [[FOR_END]]
; CHECK: for.end:
; CHECK-NEXT: ret void
;
entry:
br i1 true, label %for.preheader, label %for.end
for.preheader:
%0 = load i32, i32* %A, align 4
call void @bar(i32 %0)
br label %for.header
for.header:
%1 = phi i32 [ %0, %for.preheader ], [ %.pre, %for.body.for.body_crit_edge ]
%i = phi i64 [ 0, %for.preheader ], [ %inc, %for.body.for.body_crit_edge ]
%arrayidx = getelementptr inbounds i32, i32* %A, i64 %i
call void @bar(i32 %1)
%inc = add nsw i64 %i, 1
br i1 true, label %for.body, label %for.body.for.body_crit_edge
for.body:
%cmp = call i1 @foo(i64 %i)
br i1 %cmp, label %for.body.for.body_crit_edge, label %for.end
for.body.for.body_crit_edge:
%arrayidx.phi.trans.insert = getelementptr inbounds i32, i32* %A, i64 %inc
%.pre = load i32, i32* %arrayidx.phi.trans.insert, align 4
br label %for.header
for.end:
ret void
}
; Check that loop unroll pass correctly handle loops with
; (1) multiple exiting blocks; and
; (2) loop latch is not an exiting block.
define void @test3(i32* noalias %A, i1 %cond) {
; CHECK-LABEL: @test3(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[TMP0:%.*]] = load i32, i32* [[A:%.*]], align 4
; CHECK-NEXT: call void @bar(i32 [[TMP0]])
; CHECK-NEXT: br label [[FOR_HEADER:%.*]]
; CHECK: for.header:
; CHECK-NEXT: call void @bar(i32 [[TMP0]])
; CHECK-NEXT: br i1 [[COND:%.*]], label [[FOR_BODY:%.*]], label [[FOR_END:%.*]]
; CHECK: for.body:
; CHECK-NEXT: br label [[FOR_BODY_FOR_BODY_CRIT_EDGE:%.*]]
; CHECK: for.body.for.body_crit_edge:
; CHECK-NEXT: [[ARRAYIDX_PHI_TRANS_INSERT:%.*]] = getelementptr inbounds i32, i32* [[A]], i64 1
; CHECK-NEXT: [[DOTPRE:%.*]] = load i32, i32* [[ARRAYIDX_PHI_TRANS_INSERT]], align 4
; CHECK-NEXT: call void @bar(i32 [[DOTPRE]])
; CHECK-NEXT: br i1 [[COND]], label [[FOR_BODY_1:%.*]], label [[FOR_END]]
; CHECK: for.body.1:
; CHECK-NEXT: br label [[FOR_BODY_FOR_BODY_CRIT_EDGE_1:%.*]]
; CHECK: for.body.for.body_crit_edge.1:
; CHECK-NEXT: [[ARRAYIDX_PHI_TRANS_INSERT_1:%.*]] = getelementptr inbounds i32, i32* [[A]], i64 2
; CHECK-NEXT: [[DOTPRE_1:%.*]] = load i32, i32* [[ARRAYIDX_PHI_TRANS_INSERT_1]], align 4
; CHECK-NEXT: call void @bar(i32 [[DOTPRE_1]])
; CHECK-NEXT: br i1 [[COND]], label [[FOR_BODY_2:%.*]], label [[FOR_END]]
; CHECK: for.body.2:
; CHECK-NEXT: br label [[FOR_BODY_FOR_BODY_CRIT_EDGE_2:%.*]]
; CHECK: for.body.for.body_crit_edge.2:
; CHECK-NEXT: [[ARRAYIDX_PHI_TRANS_INSERT_2:%.*]] = getelementptr inbounds i32, i32* [[A]], i64 3
; CHECK-NEXT: [[DOTPRE_2:%.*]] = load i32, i32* [[ARRAYIDX_PHI_TRANS_INSERT_2]], align 4
; CHECK-NEXT: call void @bar(i32 [[DOTPRE_2]])
; CHECK-NEXT: br i1 [[COND]], label [[FOR_BODY_3:%.*]], label [[FOR_END]]
; CHECK: for.body.3:
; CHECK-NEXT: br i1 false, label [[FOR_BODY_FOR_BODY_CRIT_EDGE_3:%.*]], label [[FOR_END]]
; CHECK: for.body.for.body_crit_edge.3:
; CHECK-NEXT: unreachable
; CHECK: for.end:
; CHECK-NEXT: ret void
;
entry:
%0 = load i32, i32* %A, align 4
call void @bar(i32 %0)
br label %for.header
for.header:
%1 = phi i32 [ %0, %entry ], [ %.pre, %for.body.for.body_crit_edge ]
%i = phi i64 [ 0, %entry ], [ %inc, %for.body.for.body_crit_edge ]
%arrayidx = getelementptr inbounds i32, i32* %A, i64 %i
call void @bar(i32 %1)
br i1 %cond, label %for.body, label %for.end
for.body:
%inc = add nsw i64 %i, 1
%cmp = icmp slt i64 %inc, 4
br i1 %cmp, label %for.body.for.body_crit_edge, label %for.end
for.body.for.body_crit_edge:
%arrayidx.phi.trans.insert = getelementptr inbounds i32, i32* %A, i64 %inc
%.pre = load i32, i32* %arrayidx.phi.trans.insert, align 4
br label %for.header
for.end:
ret void
}
; Test it doesn't crash.
define void @test4(i32 %arg) {
; CHECK-LABEL: @test4(
; CHECK-NEXT: bb:
; CHECK-NEXT: br label [[BB1:%.*]]
; CHECK: bb1:
; CHECK-NEXT: br i1 false, label [[BB4:%.*]], label [[BB1_1:%.*]]
; CHECK: bb1.1:
; CHECK-NEXT: br i1 false, label [[BB4]], label [[BB1_2:%.*]]
; CHECK: bb1.2:
; CHECK-NEXT: br i1 false, label [[BB4]], label [[BB1_3:%.*]]
; CHECK: bb1.3:
; CHECK-NEXT: br i1 false, label [[BB4]], label [[BB1]], !llvm.loop [[LOOP2:![0-9]+]]
; CHECK: bb4:
; CHECK-NEXT: unreachable
;
bb:
br label %bb1
bb1: ; preds = %bb1, %bb
%tmp = phi i64 [ 0, %bb ], [ 65, %bb1 ]
%tmp2 = phi i32 [ %arg, %bb ], [ %tmp3, %bb1 ]
%tmp3 = add i32 0, -1880031232
br i1 false, label %bb4, label %bb1
bb4: ; preds = %bb1
unreachable
}
declare void @bar(i32)
declare i1 @foo(i64)
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