e3cf80c5c1
BlockFrequencyInfo calculates block frequencies as Scaled64 numbers but as a last step converts them to unsigned 64bit integers (`BlockFrequency`). This improves the factors picked for this conversion so that: * Avoid big numbers close to UINT64_MAX to avoid users overflowing/saturating when adding multiply frequencies together or when multiplying with integers. This leaves the topmost 10 bits unused to allow for some room. * Spread the difference between hottest/coldest block as much as possible to increase precision. * If the hot/cold spread cannot be represented loose precision at the lower end, but keep the frequencies at the upper end for hot blocks differentiable.
44 lines
1.1 KiB
LLVM
44 lines
1.1 KiB
LLVM
; RUN: opt < %s -disable-output -passes="print<block-freq>" 2>&1 | FileCheck %s
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; Sanity check precision for small-ish min/max spread.
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@g = global i32 0
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; CHECK-LABEL: block-frequency-info: func0
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; CHECK: - entry: float = 1.0, {{.*}}, count = 1000
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; CHECK: - cmp0_true: float = 0.4, {{.*}}, count = 400
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; CHECK: - cmp0_false: float = 0.6, {{.*}}, count = 600
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; CHECK: - cmp1_true: float = 0.1, {{.*}}, count = 100
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; CHECK: - cmp1_false: float = 0.3, {{.*}}, count = 300
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; CHECK: - join: float = 1.0, {{.*}}, count = 1000
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define void @func0(i32 %a0, i32 %a1) !prof !0 {
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entry:
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%cmp0 = icmp ne i32 %a0, 0
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br i1 %cmp0, label %cmp0_true, label %cmp0_false, !prof !1
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cmp0_true:
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store volatile i32 1, ptr @g
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%cmp1 = icmp ne i32 %a1, 0
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br i1 %cmp1, label %cmp1_true, label %cmp1_false, !prof !2
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cmp0_false:
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store volatile i32 2, ptr @g
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br label %join
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cmp1_true:
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store volatile i32 3, ptr @g
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br label %join
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cmp1_false:
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store volatile i32 4, ptr @g
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br label %join
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join:
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store volatile i32 5, ptr @g
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ret void
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}
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!0 = !{!"function_entry_count", i64 1000}
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!1 = !{!"branch_weights", i32 400, i32 600}
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!2 = !{!"branch_weights", i32 1, i32 3}
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