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llvm-mirror/test/Transforms/LoopUnroll/runtime-loop-branchweight.ll

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[LoopUnroll] Update branch weight for remainder loop Unrolling a loop with compile-time unknown trip count results in a remainder loop. The remainder loop executes the remaining iterations of the original loop when the original trip count is not a multiple of the unroll factor. For better profile counts maintenance throughout the optimization pipeline, I'm assigning an artificial weight to the latch branch of the remainder loop. A remainder loop runs up to as many times as the unroll factor subtracted by 1. Therefore I'm assigning the maximum possible trip count as the back edge weight. This should be more accurate than the default non-profile weight, which assumes the back edge runs much more frequently than the exit edge. Differential Revision: https://reviews.llvm.org/D83187
2020-07-05 05:24:11 +02:00
; RUN: opt < %s -S -loop-unroll -unroll-runtime=true -unroll-count=4 | FileCheck %s
; RUN: opt < %s -S -passes=loop-unroll -unroll-runtime=true -unroll-count=4 | FileCheck %s
;; Check that the remainder loop is properly assigned a branch weight for its latch branch.
; CHECK-LABEL: @test(
; CHECK-LABEL: for.body:
; CHECK: br i1 [[COND1:%.*]], label %for.end.loopexit.unr-lcssa.loopexit, label %for.body, !prof ![[#PROF:]], !llvm.loop ![[#LOOP:]]
; CHECK-LABEL: for.body.epil:
; CHECK: br i1 [[COND2:%.*]], label %for.body.epil, label %for.end.loopexit.epilog-lcssa, !prof ![[#PROF2:]], !llvm.loop ![[#LOOP2:]]
Revert "Use uint64_t for branch weights instead of uint32_t" This reverts commit 10f2a0d662d8d72eaac48d3e9b31ca8dc90df5a4. More uint64_t overflows.
2020-10-31 08:15:46 +01:00
; CHECK: ![[#PROF]] = !{!"branch_weights", i32 1, i32 9999}
; CHECK: ![[#PROF2]] = !{!"branch_weights", i32 3, i32 1}
[LoopUnroll] Update branch weight for remainder loop Unrolling a loop with compile-time unknown trip count results in a remainder loop. The remainder loop executes the remaining iterations of the original loop when the original trip count is not a multiple of the unroll factor. For better profile counts maintenance throughout the optimization pipeline, I'm assigning an artificial weight to the latch branch of the remainder loop. A remainder loop runs up to as many times as the unroll factor subtracted by 1. Therefore I'm assigning the maximum possible trip count as the back edge weight. This should be more accurate than the default non-profile weight, which assumes the back edge runs much more frequently than the exit edge. Differential Revision: https://reviews.llvm.org/D83187
2020-07-05 05:24:11 +02:00
define i3 @test(i3* %a, i3 %n) {
entry:
%cmp1 = icmp eq i3 %n, 0
br i1 %cmp1, label %for.end, label %for.body
for.body:
%indvars.iv = phi i64 [ %indvars.iv.next, %for.body ], [ 0, %entry ]
%sum.02 = phi i3 [ %add, %for.body ], [ 0, %entry ]
%arrayidx = getelementptr inbounds i3, i3* %a, i64 %indvars.iv
%0 = load i3, i3* %arrayidx
%add = add nsw i3 %0, %sum.02
%indvars.iv.next = add i64 %indvars.iv, 1
%lftr.wideiv = trunc i64 %indvars.iv.next to i3
%exitcond = icmp eq i3 %lftr.wideiv, %n
br i1 %exitcond, label %for.end, label %for.body, !prof !0
for.end:
%sum.0.lcssa = phi i3 [ 0, %entry ], [ %add, %for.body ]
ret i3 %sum.0.lcssa
}
Revert "Use uint64_t for branch weights instead of uint32_t" This reverts commit 10f2a0d662d8d72eaac48d3e9b31ca8dc90df5a4. More uint64_t overflows.
2020-10-31 08:15:46 +01:00
!0 = !{!"branch_weights", i32 1, i32 9999}
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