forked from OSchip/llvm-project
d0e42037bf
This change introduces a MIR target-independent pseudo instruction corresponding to the IR intrinsic llvm.pseudoprobe for pseudo-probe block instrumentation. Please refer to https://reviews.llvm.org/D86193 for the whole story. An `llvm.pseudoprobe` intrinsic call will be lowered into a target-independent operation named `PSEUDO_PROBE`. Given the following instrumented IR, ``` define internal void @foo2(i32 %x, void (i32)* %f) !dbg !4 { bb0: %cmp = icmp eq i32 %x, 0 call void @llvm.pseudoprobe(i64 837061429793323041, i64 1) br i1 %cmp, label %bb1, label %bb2 bb1: call void @llvm.pseudoprobe(i64 837061429793323041, i64 2) br label %bb3 bb2: call void @llvm.pseudoprobe(i64 837061429793323041, i64 3) br label %bb3 bb3: call void @llvm.pseudoprobe(i64 837061429793323041, i64 4) ret void } ``` the corresponding MIR is shown below. Note that block `bb3` is duplicated into `bb1` and `bb2` where its probe is duplicated too. This allows for an accurate execution count to be collected for `bb3`, which is basically the sum of the counts of `bb1` and `bb2`. ``` bb.0.bb0: frame-setup PUSH64r undef $rax, implicit-def $rsp, implicit $rsp TEST32rr killed renamable $edi, renamable $edi, implicit-def $eflags PSEUDO_PROBE 837061429793323041, 1, 0 $edi = MOV32ri 1, debug-location !13; test.c:0 JCC_1 %bb.1, 4, implicit $eflags bb.2.bb2: PSEUDO_PROBE 837061429793323041, 3, 0 PSEUDO_PROBE 837061429793323041, 4, 0 $rax = frame-destroy POP64r implicit-def $rsp, implicit $rsp RETQ bb.1.bb1: PSEUDO_PROBE 837061429793323041, 2, 0 PSEUDO_PROBE 837061429793323041, 4, 0 $rax = frame-destroy POP64r implicit-def $rsp, implicit $rsp RETQ ``` The target op PSEUDO_PROBE will be converted into a piece of binary data by the object emitter with no machine instructions generated. This is done in a different patch. Reviewed By: wmi Differential Revision: https://reviews.llvm.org/D86495 |
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| llvm.spec.in | ||
README.txt
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