maxjhandsome
/
llvm-project
forked from OSchip/llvm-project
1
0
Fork 0
Code Issues Pull Requests Packages Releases Wiki Activity
llvm-project/llvm/test/CodeGen/X86/xray-loop-detection.ll

24 lines
648 B
LLVM
Raw Normal View History

[XRay] Detect loops in functions being lowered Summary: This is an implementation of the loop detection logic that XRay needs to determine whether a function might take time at runtime. Without this heuristic, XRay will tend to not instrument short functions that have loops that might have runtime dependent on inputs or external values. While this implementation doesn't do any further analysis than just figuring out whether there is a loop in the MachineFunction being code-gen'ed, we're paving the way for being able to perform more sophisticated analysis of the function in the future (for example to determine whether the trip count for the loop might be constant, and make a decision on that instead). This enables us to cover more functions with the default heuristics, and potentially identify ones that have variable runtime latency just by looking for the presence of loops. Reviewers: chandlerc, rnk, pelikan Subscribers: llvm-commits Differential Revision: https://reviews.llvm.org/D32274 llvm-svn: 302103
2017-05-04 09:24:26 +08:00
; RUN: llc -filetype=asm -o - -mtriple=x86_64-unknown-linux-gnu < %s | FileCheck %s
; RUN: llc -filetype=asm -o - -mtriple=x86_64-darwin-unknown < %s | FileCheck %s
define i32 @foo(i32 %i) nounwind noinline uwtable "xray-instruction-threshold"="1" {
entry:
br label %Test
Test:
%indvar = phi i32 [0, %entry], [%nextindvar, %Inc]
%cond = icmp eq i32 %indvar, %i
br i1 %cond, label %Exit, label %Inc
Inc:
%nextindvar = add i32 %indvar, 1
br label %Test
Exit:
%retval = phi i32 [%indvar, %Test]
ret i32 %retval
}
; CHECK-LABEL: xray_sled_0:
; CHECK-NEXT: .ascii "\353\t"
; CHECK-NEXT: nopw 512(%rax,%rax)
Revert r311525: "[XRay][CodeGen] Use PIC-friendly code in XRay sleds; remove synthetic references in .text" Breaks builds internally. Will forward repo instructions to author. llvm-svn: 312243
2017-08-31 23:17:17 +08:00
; CHECK-LABEL: Ltmp0:
[XRay] Detect loops in functions being lowered Summary: This is an implementation of the loop detection logic that XRay needs to determine whether a function might take time at runtime. Without this heuristic, XRay will tend to not instrument short functions that have loops that might have runtime dependent on inputs or external values. While this implementation doesn't do any further analysis than just figuring out whether there is a loop in the MachineFunction being code-gen'ed, we're paving the way for being able to perform more sophisticated analysis of the function in the future (for example to determine whether the trip count for the loop might be constant, and make a decision on that instead). This enables us to cover more functions with the default heuristics, and potentially identify ones that have variable runtime latency just by looking for the presence of loops. Reviewers: chandlerc, rnk, pelikan Subscribers: llvm-commits Differential Revision: https://reviews.llvm.org/D32274 llvm-svn: 302103
2017-05-04 09:24:26 +08:00