294f3ce5dd
…f weights" #95136 Reverts #95060, and relands #86609, with the unintended code generation changes addressed. This patch implements the changes to LLVM IR discussed in https://discourse.llvm.org/t/rfc-update-branch-weights-metadata-to-allow-tracking-branch-weight-origins/75032 In this patch, we add an optional field to MD_prof meatdata nodes for branch weights, which can be used to distinguish weights added from llvm.expect* intrinsics from those added via other methods, e.g. from profiles or inserted by the compiler. One of the major motivations, is for use with MisExpect diagnostics, which need to know if branch_weight metadata originates from an llvm.expect intrinsic. Without that information, we end up checking branch weights multiple times in the case if ThinLTO + SampleProfiling, leading to some inaccuracy in how we report MisExpect related diagnostics to users. Since we change the format of MD_prof metadata in a fundamental way, we need to update code handling branch weights in a number of places. We also update the lang ref for branch weights to reflect the change.
57 lines
1.6 KiB
LLVM
57 lines
1.6 KiB
LLVM
; RUN: opt -passes=lower-expect -S -o - < %s | FileCheck %s
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; RUN: opt -S -passes='function(lower-expect)' < %s | FileCheck %s
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; return __builtin_expect((a > b ? 1, goo(), 0);
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;
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; Function Attrs: noinline nounwind uwtable
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define i32 @foo(i32 %arg, i32 %arg1) {
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; CHECK-LABEL: i32 @foo
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bb:
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%tmp5 = icmp sgt i32 %arg, %arg1
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br i1 %tmp5, label %bb9, label %bb7
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; CHECK: br i1 %tmp5{{.*}}!prof [[WEIGHT:![0-9]+]]
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bb7: ; preds = %bb
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%tmp8 = call i32 @goo()
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br label %bb9
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bb9: ; preds = %bb7, %bb9
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%tmp10 = phi i32 [ 1, %bb ], [ %tmp8, %bb7 ]
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%tmp11 = sext i32 %tmp10 to i64
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%expect = call i64 @llvm.expect.i64(i64 %tmp11, i64 0)
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%tmp12 = trunc i64 %expect to i32
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ret i32 %tmp12
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}
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define i32 @foo2(i32 %arg, i32 %arg1) {
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bb:
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%tmp5 = icmp sgt i32 %arg, %arg1
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br i1 %tmp5, label %bb6, label %bb7
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; CHECK: br i1 %tmp5{{.*}}!prof [[WEIGHT:![0-9]+]]
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bb6: ; preds = %bb
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br label %bb9
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bb7: ; preds = %bb
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%tmp8 = call i32 @goo()
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br label %bb9
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bb9: ; preds = %bb7, %bb6
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%tmp10 = phi i32 [ 1, %bb6 ], [ %tmp8, %bb7 ]
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%tmp11 = sext i32 %tmp10 to i64
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%expect = call i64 @llvm.expect.i64(i64 %tmp11, i64 0)
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%tmp12 = trunc i64 %expect to i32
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ret i32 %tmp12
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}
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declare i32 @goo()
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declare i64 @llvm.expect.i64(i64, i64)
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!llvm.ident = !{!0}
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!0 = !{!"clang version 5.0.0 (trunk 302965)"}
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; CHECK: [[WEIGHT]] = !{!"branch_weights", !"expected", i32 1, i32 2000}
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