[all-commits] [llvm/llvm-project] d0e420: [CSSPGO] MIR target-independent pseudo instruction...

[Hongtao Yu via All-commits]

  Branch: refs/heads/master
  Home:   https://github.com/llvm/llvm-project
  Commit: d0e42037bf0ce110cc8c6e9b536687fa40e90b99
      https://github.com/llvm/llvm-project/commit/d0e42037bf0ce110cc8c6e9b536687fa40e90b99
  Author: Hongtao Yu <hoy at fb.com>
  Date:   2020-11-20 (Fri, 20 Nov 2020)

  Changed paths:
    M llvm/include/llvm/CodeGen/ISDOpcodes.h
    M llvm/include/llvm/CodeGen/MachineInstr.h
    M llvm/include/llvm/CodeGen/SelectionDAG.h
    M llvm/include/llvm/CodeGen/SelectionDAGNodes.h
    M llvm/include/llvm/Support/TargetOpcodes.def
    M llvm/include/llvm/Target/Target.td
    M llvm/lib/CodeGen/SelectionDAG/InstrEmitter.cpp
    M llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
    M llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
    M llvm/lib/CodeGen/SelectionDAG/SelectionDAGDumper.cpp
    M llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
    A llvm/test/Transforms/SampleProfile/pseudo-probe.mir

  Log Message:
  -----------
  [CSSPGO] MIR target-independent pseudo instruction for pseudo-probe intrinsic

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