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llvm-project/llvm/test/Transforms/LoopRotate/update-branch-weights.ll
Haohai Wen 896037c75a
[LoopRotate] Set loop back edge weight to not less than exit weight (#86496) 
Branch weight from sample-based PGO may be not inaccurate due to
sampling. If the loop body must be executed, then origin loop back
edge weight must be not less than exit weight.
2024-03-28 20:07:15 +08:00

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; RUN: opt < %s -passes='print<block-freq>' -disable-output 2>&1 | FileCheck %s --check-prefixes=BFI_BEFORE
; RUN: opt < %s -passes='loop(loop-rotate),print<block-freq>' -disable-output 2>&1 | FileCheck %s --check-prefixes=BFI_AFTER
; RUN: opt < %s -passes='loop(loop-rotate)' -S | FileCheck %s --check-prefixes=IR
@g = global i32 0
; We should get the same "count =" results for "outer_loop_body" and
; "inner_loop_body" before and after the transformation.
; BFI_BEFORE-LABEL: block-frequency-info: func0
; BFI_BEFORE: - entry: {{.*}} count = 1
; BFI_BEFORE: - outer_loop_header: {{.*}} count = 1001
; BFI_BEFORE: - outer_loop_body: {{.*}} count = 1000
; BFI_BEFORE: - inner_loop_header: {{.*}} count = 4000
; BFI_BEFORE: - inner_loop_body: {{.*}} count = 3000
; BFI_BEFORE: - inner_loop_exit: {{.*}} count = 1000
; BFI_BEFORE: - outer_loop_exit: {{.*}} count = 1
; BFI_AFTER-LABEL: block-frequency-info: func0
; BFI_AFTER: - entry: {{.*}} count = 1
; BFI_AFTER: - outer_loop_body: {{.*}} count = 1000
; BFI_AFTER: - inner_loop_body: {{.*}} count = 3000
; BFI_AFTER: - inner_loop_exit: {{.*}} count = 1000
; BFI_AFTER: - outer_loop_exit: {{.*}} count = 1
; IR-LABEL: define void @func0
; IR: inner_loop_body:
; IR: br i1 %cmp1, label %inner_loop_body, label %inner_loop_exit, !prof [[PROF_FUNC0_0:![0-9]+]]
; IR: inner_loop_exit:
; IR: br i1 %cmp0, label %outer_loop_body, label %outer_loop_exit, !prof [[PROF_FUNC0_1:![0-9]+]]
;
; A function with known loop-bounds where after loop-rotation we end with an
; unconditional branch in the pre-header.
define void @func0() !prof !0 {
entry:
br label %outer_loop_header
outer_loop_header:
%i0 = phi i32 [0, %entry], [%i0_inc, %inner_loop_exit]
%cmp0 = icmp slt i32 %i0, 1000
br i1 %cmp0, label %outer_loop_body, label %outer_loop_exit, !prof !1
outer_loop_body:
store volatile i32 %i0, ptr @g, align 4
br label %inner_loop_header
inner_loop_header:
%i1 = phi i32 [0, %outer_loop_body], [%i1_inc, %inner_loop_body]
%cmp1 = icmp slt i32 %i1, 3
br i1 %cmp1, label %inner_loop_body, label %inner_loop_exit, !prof !2
inner_loop_body:
store volatile i32 %i1, ptr @g, align 4
%i1_inc = add i32 %i1, 1
br label %inner_loop_header
inner_loop_exit:
%i0_inc = add i32 %i0, 1
br label %outer_loop_header
outer_loop_exit:
ret void
}
; BFI_BEFORE-LABEL: block-frequency-info: func1
; BFI_BEFORE: - entry: {{.*}} count = 1024
; BFI_BEFORE: - loop_header: {{.*}} count = 21504
; BFI_BEFORE: - loop_body: {{.*}} count = 20480
; BFI_BEFORE: - loop_exit: {{.*}} count = 1024
; BFI_AFTER-LABEL: block-frequency-info: func1
; BFI_AFTER: - entry: {{.*}} count = 1024
; BFI_AFTER: - loop_body.lr.ph: {{.*}} count = 1016
; BFI_AFTER: - loop_body: {{.*}} count = 20480
; BFI_AFTER: - loop_header.loop_exit_crit_edge: {{.*}} count = 1016
; BFI_AFTER: - loop_exit: {{.*}} count = 1024
; IR-LABEL: define void @func1
; IR: entry:
; IR: br i1 %cmp1, label %loop_body.lr.ph, label %loop_exit, !prof [[PROF_FUNC1_0:![0-9]+]]
; IR: loop_body:
; IR: br i1 %cmp, label %loop_body, label %loop_header.loop_exit_crit_edge, !prof [[PROF_FUNC1_1:![0-9]+]]
; A function with unknown loop-bounds so loop-rotation ends up with a
; condition jump in pre-header and loop body. branch_weight shows body is
; executed more often than header.
define void @func1(i32 %n) !prof !3 {
entry:
br label %loop_header
loop_header:
%i = phi i32 [0, %entry], [%i_inc, %loop_body]
%cmp = icmp slt i32 %i, %n
br i1 %cmp, label %loop_body, label %loop_exit, !prof !4
loop_body:
store volatile i32 %i, ptr @g, align 4
%i_inc = add i32 %i, 1
br label %loop_header
loop_exit:
ret void
}
; BFI_BEFORE-LABEL: block-frequency-info: func2
; BFI_BEFORE: - entry: {{.*}} count = 1024
; BFI_BEFORE: - loop_header: {{.*}} count = 1056
; BFI_BEFORE: - loop_body: {{.*}} count = 32
; BFI_BEFORE: - loop_exit: {{.*}} count = 1024
; BFI_AFTER-LABEL: block-frequency-info: func2
; - entry: {{.*}} count = 1024
; - loop_body.lr.ph: {{.*}} count = 32
; - loop_body: {{.*}} count = 32
; - loop_header.loop_exit_crit_edge: {{.*}} count = 32
; - loop_exit: {{.*}} count = 1024
; IR-LABEL: define void @func2
; IR: entry:
; IR: br i1 %cmp1, label %loop_exit, label %loop_body.lr.ph, !prof [[PROF_FUNC2_0:![0-9]+]]
; IR: loop_body:
; IR: br i1 %cmp, label %loop_header.loop_exit_crit_edge, label %loop_body, !prof [[PROF_FUNC2_1:![0-9]+]]
; A function with unknown loop-bounds so loop-rotation ends up with a
; condition jump in pre-header and loop body. Similar to `func1` but here
; loop-exit count is higher than backedge count.
define void @func2(i32 %n) !prof !3 {
entry:
br label %loop_header
loop_header:
%i = phi i32 [0, %entry], [%i_inc, %loop_body]
%cmp = icmp slt i32 %i, %n
br i1 %cmp, label %loop_exit, label %loop_body, !prof !5
loop_body:
store volatile i32 %i, ptr @g, align 4
%i_inc = add i32 %i, 1
br label %loop_header
loop_exit:
ret void
}
; BFI_BEFORE-LABEL: block-frequency-info: func3_zero_branch_weight
; BFI_BEFORE: - entry: {{.*}} count = 1024
; BFI_BEFORE: - loop_header: {{.*}} count = 2199023255552
; BFI_BEFORE: - loop_body: {{.*}} count = 2199023254528
; BFI_BEFORE: - loop_exit: {{.*}} count = 1024
; BFI_AFTER-LABEL: block-frequency-info: func3_zero_branch_weight
; BFI_AFTER: - entry: {{.*}} count = 1024
; BFI_AFTER: - loop_body.lr.ph: {{.*}} count = 1024
; BFI_AFTER: - loop_body: {{.*}} count = 2199023255552
; BFI_AFTER: - loop_header.loop_exit_crit_edge: {{.*}} count = 1024
; BFI_AFTER: - loop_exit: {{.*}} count = 1024
; IR-LABEL: define void @func3_zero_branch_weight
; IR: entry:
; IR: br i1 %cmp1, label %loop_exit, label %loop_body.lr.ph, !prof [[PROF_FUNC3_0:![0-9]+]]
; IR: loop_body:
; IR: br i1 %cmp, label %loop_header.loop_exit_crit_edge, label %loop_body, !prof [[PROF_FUNC3_0]]
define void @func3_zero_branch_weight(i32 %n) !prof !3 {
entry:
br label %loop_header
loop_header:
%i = phi i32 [0, %entry], [%i_inc, %loop_body]
%cmp = icmp slt i32 %i, %n
br i1 %cmp, label %loop_exit, label %loop_body, !prof !6
loop_body:
store volatile i32 %i, ptr @g, align 4
%i_inc = add i32 %i, 1
br label %loop_header
loop_exit:
ret void
}
; IR-LABEL: define void @func4_zero_branch_weight
; IR: entry:
; IR: br i1 %cmp1, label %loop_exit, label %loop_body.lr.ph, !prof [[PROF_FUNC4_0:![0-9]+]]
; IR: loop_body:
; IR: br i1 %cmp, label %loop_header.loop_exit_crit_edge, label %loop_body, !prof [[PROF_FUNC4_0]]
define void @func4_zero_branch_weight(i32 %n) !prof !3 {
entry:
br label %loop_header
loop_header:
%i = phi i32 [0, %entry], [%i_inc, %loop_body]
%cmp = icmp slt i32 %i, %n
br i1 %cmp, label %loop_exit, label %loop_body, !prof !7
loop_body:
store volatile i32 %i, ptr @g, align 4
%i_inc = add i32 %i, 1
br label %loop_header
loop_exit:
ret void
}
; IR-LABEL: define void @func5_zero_branch_weight
; IR: entry:
; IR: br i1 %cmp1, label %loop_exit, label %loop_body.lr.ph, !prof [[PROF_FUNC5_0:![0-9]+]]
; IR: loop_body:
; IR: br i1 %cmp, label %loop_header.loop_exit_crit_edge, label %loop_body, !prof [[PROF_FUNC5_0]]
define void @func5_zero_branch_weight(i32 %n) !prof !3 {
entry:
br label %loop_header
loop_header:
%i = phi i32 [0, %entry], [%i_inc, %loop_body]
%cmp = icmp slt i32 %i, %n
br i1 %cmp, label %loop_exit, label %loop_body, !prof !8
loop_body:
store volatile i32 %i, ptr @g, align 4
%i_inc = add i32 %i, 1
br label %loop_header
loop_exit:
ret void
}
; BFI_BEFORE-LABEL: block-frequency-info: func6_inaccurate_branch_weight
; BFI_BEFORE: - entry: {{.*}} count = 1024
; BFI_BEFORE: - loop_header: {{.*}} count = 2047
; BFI_BEFORE: - loop_body: {{.*}} count = 1023
; BFI_BEFORE: - loop_exit: {{.*}} count = 1024
; BFI_AFTER-LABEL: block-frequency-info: func6_inaccurate_branch_weight
; BFI_AFTER: - entry: {{.*}} count = 1024
; BFI_AFTER: - loop_body: {{.*}} count = 1024
; BFI_AFTER: - loop_exit: {{.*}} count = 1024
; IR-LABEL: define void @func6_inaccurate_branch_weight(
; IR: entry:
; IR: br label %loop_body
; IR: loop_body:
; IR: br i1 %cmp, label %loop_body, label %loop_exit, !prof [[PROF_FUNC6_0:![0-9]+]]
; IR: loop_exit:
; IR: ret void
; Branch weight from sample-based PGO may be inaccurate due to sampling.
; Count for loop_body in following case should be not less than loop_exit.
; However this may not hold for Sample-based PGO.
define void @func6_inaccurate_branch_weight() !prof !3 {
entry:
br label %loop_header
loop_header:
%i = phi i32 [0, %entry], [%i_inc, %loop_body]
%cmp = icmp slt i32 %i, 2
br i1 %cmp, label %loop_body, label %loop_exit, !prof !9
loop_body:
store volatile i32 %i, ptr @g, align 4
%i_inc = add i32 %i, 1
br label %loop_header
loop_exit:
ret void
}
!0 = !{!"function_entry_count", i64 1}
!1 = !{!"branch_weights", i32 1000, i32 1}
!2 = !{!"branch_weights", i32 3000, i32 1000}
!3 = !{!"function_entry_count", i64 1024}
!4 = !{!"branch_weights", i32 40, i32 2}
!5 = !{!"branch_weights", i32 10240, i32 320}
!6 = !{!"branch_weights", i32 0, i32 1}
!7 = !{!"branch_weights", i32 1, i32 0}
!8 = !{!"branch_weights", i32 0, i32 0}
!9 = !{!"branch_weights", i32 1023, i32 1024}
; IR: [[PROF_FUNC0_0]] = !{!"branch_weights", i32 2000, i32 1000}
; IR: [[PROF_FUNC0_1]] = !{!"branch_weights", i32 999, i32 1}
; IR: [[PROF_FUNC1_0]] = !{!"branch_weights", i32 127, i32 1}
; IR: [[PROF_FUNC1_1]] = !{!"branch_weights", i32 2433, i32 127}
; IR: [[PROF_FUNC2_0]] = !{!"branch_weights", i32 9920, i32 320}
; IR: [[PROF_FUNC2_1]] = !{!"branch_weights", i32 320, i32 0}
; IR: [[PROF_FUNC3_0]] = !{!"branch_weights", i32 0, i32 1}
; IR: [[PROF_FUNC4_0]] = !{!"branch_weights", i32 1, i32 0}
; IR: [[PROF_FUNC5_0]] = !{!"branch_weights", i32 0, i32 0}
; IR: [[PROF_FUNC6_0]] = !{!"branch_weights", i32 0, i32 1024}
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