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llvm/test/Transforms/LoopUnroll/runtime-loop-multiple-exits.ll
Anna Thomas f6b4a0347c [RuntimeUnrolling] Add logic for loops with multiple exit blocks 
Summary:
Runtime unrolling is done for loops with a single exit block and a
single exiting block (and this exiting block should be the latch block).
This patch adds logic to support unrolling in the presence of multiple exit
blocks (which also means multiple exiting blocks).
Currently this is under an off-by-default option and is supported when
epilog code is generated. Support in presence of prolog code will be in
a future patch (we just need to add more tests, and update comments).

This patch is essentially an implementation patch. I have not added any
heuristic (in terms of branches added or code size) to decide when
this should be enabled.

Reviewers: mkuper, sanjoy, reames, evstupac

Reviewed by: reames

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D33001

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@306846 91177308-0d34-0410-b5e6-96231b3b80d8
2017-06-30 17:57:07 +00:00

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; RUN: opt < %s -loop-unroll -unroll-runtime=true -unroll-runtime-epilog=true -unroll-runtime-multi-exit=true -verify-dom-info -verify-loop-info -instcombine -S| FileCheck %s
; RUN: opt < %s -loop-unroll -unroll-runtime -unroll-count=2 -unroll-runtime-epilog=true -unroll-runtime-multi-exit=true -verify-dom-info -verify-loop-info -instcombine
; the second RUN generates an epilog remainder block for all the test
; cases below (it does not generate a loop).
; test with three exiting and three exit blocks.
; none of the exit blocks have successors
define void @test1(i64 %trip, i1 %cond) {
; CHECK-LABEL: test1
; CHECK-NEXT: entry:
; CHECK-NEXT: [[TMP0:%.*]] = add i64 [[TRIP:%.*]], -1
; CHECK-NEXT: [[XTRAITER:%.*]] = and i64 [[TRIP]], 7
; CHECK-NEXT: [[TMP1:%.*]] = icmp ult i64 [[TMP0]], 7
; CHECK-NEXT: br i1 [[TMP1]], label %exit2.loopexit.unr-lcssa, label [[ENTRY_NEW:%.*]]
; CHECK: entry.new:
; CHECK-NEXT: [[UNROLL_ITER:%.*]] = sub i64 [[TRIP]], [[XTRAITER]]
; CHECK-NEXT: br label [[LOOP_HEADER:%.*]]
; CHECK-LABEL: loop_latch.epil:
; CHECK-NEXT: %epil.iter.sub = add i64 %epil.iter, -1
; CHECK-NEXT: %epil.iter.cmp = icmp eq i64 %epil.iter.sub, 0
; CHECK-NEXT: br i1 %epil.iter.cmp, label %exit2.loopexit.epilog-lcssa, label %loop_header.epil
; CHECK-LABEL: loop_latch.7:
; CHECK-NEXT: %niter.nsub.7 = add i64 %niter, -8
; CHECK-NEXT: %niter.ncmp.7 = icmp eq i64 %niter.nsub.7, 0
; CHECK-NEXT: br i1 %niter.ncmp.7, label %exit2.loopexit.unr-lcssa.loopexit, label %loop_header
entry:
br label %loop_header
loop_header:
%iv = phi i64 [ 0, %entry ], [ %iv_next, %loop_latch ]
br i1 %cond, label %loop_latch, label %loop_exiting_bb1
loop_exiting_bb1:
br i1 false, label %loop_exiting_bb2, label %exit1
loop_exiting_bb2:
br i1 false, label %loop_latch, label %exit3
exit3:
ret void
loop_latch:
%iv_next = add i64 %iv, 1
%cmp = icmp ne i64 %iv_next, %trip
br i1 %cmp, label %loop_header, label %exit2.loopexit
exit1:
ret void
exit2.loopexit:
ret void
}
; test with three exiting and two exit blocks.
; The non-latch exit block has 2 unique predecessors.
; There are 2 values passed to the exit blocks that are calculated at every iteration.
; %sum.02 and %add. Both of these are incoming values for phi from every exiting
; unrolled block.
define i32 @test2(i32* nocapture %a, i64 %n) {
; CHECK-LABEL: test2
; CHECK-LABEL: for.exit2.loopexit:
; CHECK-NEXT: %retval.ph = phi i32 [ 42, %for.exiting_block ], [ %sum.02, %header ], [ %add, %for.body ], [ 42, %for.exiting_block.1 ], [ %add.1, %for.body.1 ], [ 42, %for.exiting_block.2 ], [ %add.2, %for.body.2 ], [ 42, %for.exiting_block.3 ],
; CHECK-NEXT: br label %for.exit2
; CHECK-LABEL: for.exit2.loopexit2:
; CHECK-NEXT: %retval.ph3 = phi i32 [ 42, %for.exiting_block.epil ], [ %sum.02.epil, %header.epil ]
; CHECK-NEXT: br label %for.exit2
; CHECK-LABEL: for.exit2:
; CHECK-NEXT: %retval = phi i32 [ %retval.ph, %for.exit2.loopexit ], [ %retval.ph3, %for.exit2.loopexit2 ]
; CHECK-NEXT: ret i32 %retval
; CHECK: %niter.nsub.7 = add i64 %niter, -8
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 ]
br i1 false, label %for.exit2, label %for.exiting_block
for.exiting_block:
%cmp = icmp eq i64 %n, 42
br i1 %cmp, label %for.exit2, label %for.body
for.body:
%arrayidx = getelementptr inbounds i32, i32* %a, i64 %indvars.iv
%0 = load i32, i32* %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: ; preds = %for.body
%sum.0.lcssa = phi i32 [ %add, %for.body ]
ret i32 %sum.0.lcssa
for.exit2:
%retval = phi i32 [ %sum.02, %header ], [ 42, %for.exiting_block ]
ret i32 %retval
}
; test with two exiting and three exit blocks.
; the non-latch exiting block has a switch.
define void @test3(i64 %trip, i64 %add) {
; CHECK-LABEL: test3
; CHECK-NEXT: entry:
; CHECK-NEXT: [[TMP0:%.*]] = add i64 [[TRIP:%.*]], -1
; CHECK-NEXT: [[XTRAITER:%.*]] = and i64 [[TRIP]], 7
; CHECK-NEXT: [[TMP1:%.*]] = icmp ult i64 [[TMP0]], 7
; CHECK-NEXT: br i1 [[TMP1]], label %exit2.loopexit.unr-lcssa, label [[ENTRY_NEW:%.*]]
; CHECK: entry.new:
; CHECK-NEXT: %unroll_iter = sub i64 [[TRIP]], [[XTRAITER]]
; CHECK-NEXT: br label [[LOOP_HEADER:%.*]]
; CHECK-LABEL: loop_header:
; CHECK-NEXT: %sum = phi i64 [ 0, %entry.new ], [ %sum.next.7, %loop_latch.7 ]
; CHECK-NEXT: %niter = phi i64 [ %unroll_iter, %entry.new ], [ %niter.nsub.7, %loop_latch.7 ]
; CHECK-LABEL: loop_exiting_bb1.7:
; CHECK-NEXT: switch i64 %sum.next.6, label %loop_latch.7
; CHECK-LABEL: loop_latch.7:
; CHECK-NEXT: %sum.next.7 = add i64 %sum.next.6, %add
; CHECK-NEXT: %niter.nsub.7 = add i64 %niter, -8
; CHECK-NEXT: %niter.ncmp.7 = icmp eq i64 %niter.nsub.7, 0
; CHECK-NEXT: br i1 %niter.ncmp.7, label %exit2.loopexit.unr-lcssa.loopexit, label %loop_header
entry:
br label %loop_header
loop_header:
%iv = phi i64 [ 0, %entry ], [ %iv_next, %loop_latch ]
%sum = phi i64 [ 0, %entry ], [ %sum.next, %loop_latch ]
br i1 undef, label %loop_latch, label %loop_exiting_bb1
loop_exiting_bb1:
switch i64 %sum, label %loop_latch [
i64 24, label %exit1
i64 42, label %exit3
]
exit3:
ret void
loop_latch:
%iv_next = add nuw nsw i64 %iv, 1
%sum.next = add i64 %sum, %add
%cmp = icmp ne i64 %iv_next, %trip
br i1 %cmp, label %loop_header, label %exit2.loopexit
exit1:
ret void
exit2.loopexit:
ret void
}
; FIXME: Support multiple exiting blocks to the same latch exit block.
define i32 @test4(i32* nocapture %a, i64 %n, i1 %cond) {
; CHECK-LABEL: test4
; CHECK-NOT: .unr
; CHECK-NOT: .epil
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 ]
br i1 %cond, label %for.end, label %for.exiting_block
for.exiting_block:
%cmp = icmp eq i64 %n, 42
br i1 %cmp, label %for.exit2, label %for.body
for.body: ; preds = %for.body, %entry
%arrayidx = getelementptr inbounds i32, i32* %a, i64 %indvars.iv
%0 = load i32, i32* %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: ; preds = %for.body, %entry
%sum.0.lcssa = phi i32 [ 0, %header ], [ %add, %for.body ]
ret i32 %sum.0.lcssa
for.exit2:
ret i32 42
}
; two exiting and two exit blocks.
; the non-latch exiting block has duplicate edges to the non-latch exit block.
define i64 @test5(i64 %trip, i64 %add, i1 %cond) {
; CHECK-LABEL: test5
; CHECK-LABEL: exit1.loopexit:
; CHECK-NEXT: %result.ph = phi i64 [ %ivy, %loop_exiting ], [ %ivy, %loop_exiting ], [ %ivy.1, %loop_exiting.1 ], [ %ivy.1, %loop_exiting.1 ], [ %ivy.2, %loop_exiting.2 ],
; CHECK-NEXT: br label %exit1
; CHECK-LABEL: exit1.loopexit2:
; CHECK-NEXT: %ivy.epil = add i64 %iv.epil, %add
; CHECK-NEXT: br label %exit1
; CHECK-LABEL: exit1:
; CHECK-NEXT: %result = phi i64 [ %result.ph, %exit1.loopexit ], [ %ivy.epil, %exit1.loopexit2 ]
; CHECK-NEXT: ret i64 %result
; CHECK-LABEL: loop_latch.7:
; CHECK: %niter.nsub.7 = add i64 %niter, -8
entry:
br label %loop_header
loop_header:
%iv = phi i64 [ 0, %entry ], [ %iv_next, %loop_latch ]
%sum = phi i64 [ 0, %entry ], [ %sum.next, %loop_latch ]
br i1 %cond, label %loop_latch, label %loop_exiting
loop_exiting:
%ivy = add i64 %iv, %add
switch i64 %sum, label %loop_latch [
i64 24, label %exit1
i64 42, label %exit1
]
loop_latch:
%iv_next = add nuw nsw i64 %iv, 1
%sum.next = add i64 %sum, %add
%cmp = icmp ne i64 %iv_next, %trip
br i1 %cmp, label %loop_header, label %latchexit
exit1:
%result = phi i64 [ %ivy, %loop_exiting ], [ %ivy, %loop_exiting ]
ret i64 %result
latchexit:
ret i64 %sum.next
}
; test when exit blocks have successors.
define i32 @test6(i32* nocapture %a, i64 %n, i1 %cond, i32 %x) {
; CHECK-LABEL: test6
; CHECK-LABEL: for.exit2.loopexit:
; CHECK-NEXT: %retval.ph = phi i32 [ 42, %for.exiting_block ], [ %sum.02, %header ], [ %add, %latch ], [ 42, %for.exiting_block.1 ], [ %add.1, %latch.1 ], [ 42, %for.exiting_block.2 ], [ %add.2, %latch.2 ],
; CHECK-NEXT: br label %for.exit2
; CHECK-LABEL: for.exit2.loopexit2:
; CHECK-NEXT: %retval.ph3 = phi i32 [ 42, %for.exiting_block.epil ], [ %sum.02.epil, %header.epil ]
; CHECK-NEXT: br label %for.exit2
; CHECK-LABEL: for.exit2:
; CHECK-NEXT: %retval = phi i32 [ %retval.ph, %for.exit2.loopexit ], [ %retval.ph3, %for.exit2.loopexit2 ]
; CHECK-NEXT: br i1 %cond, label %exit_true, label %exit_false
; CHECK-LABEL: latch.7:
; CHECK: %niter.nsub.7 = add i64 %niter, -8
entry:
br label %header
header:
%indvars.iv = phi i64 [ %indvars.iv.next, %latch ], [ 0, %entry ]
%sum.02 = phi i32 [ %add, %latch ], [ 0, %entry ]
br i1 false, label %for.exit2, label %for.exiting_block
for.exiting_block:
%cmp = icmp eq i64 %n, 42
br i1 %cmp, label %for.exit2, label %latch
latch:
%arrayidx = getelementptr inbounds i32, i32* %a, i64 %indvars.iv
%load = load i32, i32* %arrayidx, align 4
%add = add nsw i32 %load, %sum.02
%indvars.iv.next = add i64 %indvars.iv, 1
%exitcond = icmp eq i64 %indvars.iv.next, %n
br i1 %exitcond, label %latch_exit, label %header
latch_exit:
%sum.0.lcssa = phi i32 [ %add, %latch ]
ret i32 %sum.0.lcssa
for.exit2:
%retval = phi i32 [ %sum.02, %header ], [ 42, %for.exiting_block ]
%addx = add i32 %retval, %x
br i1 %cond, label %exit_true, label %exit_false
exit_true:
ret i32 %retval
exit_false:
ret i32 %addx
}
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