## This checks that shrink wrapping does not pessimize a CFG pattern where two ## blocks can be proved to have the same execution count but, because of profile ## inaccuricies, we could move saves into the second block. We can prove two ## blocks have the same frequency when B post-dominate A and A dominates B and ## are at the same loop nesting level. This would be a pessimization because ## shrink wrapping is unlikely to be able to cleanly move PUSH instructions, ## inserting additional store instructions. # REQUIRES: system-linux # RUN: llvm-mc -filetype=obj -triple x86_64-unknown-unknown \ # RUN: %s -o %t.o # RUN: link_fdata %s %t.o %t.fdata # RUN: llvm-strip --strip-unneeded %t.o # RUN: %clang %cflags %t.o -o %t.exe -Wl,-q -nostdlib # RUN: llvm-bolt -relocs %t.exe -o %t.out -data %t.fdata \ # RUN: -frame-opt=all -equalize-bb-counts | FileCheck %s ## Here we create a CFG pattern with two blocks A and B belonging to the same ## equivalency class as defined by dominance relations and having in theory ## the same frequency. But we tweak edge counts from profile to make block A ## hotter than block B. .globl _start .type _start, %function _start: .cfi_startproc ## Hot prologue # FDATA: 0 [unknown] 0 1 _start 0 0 10 push %rbp mov %rsp, %rbp push %rbx push %r14 subq $0x20, %rsp b: je end_if_1 # FDATA: 1 _start #b# 1 _start #end_if_1# 0 1 if_false: movq rel(%rip), %rdi # Add this to create a relocation and run bolt w/ relocs c: jmp end_if_1 ## Reduce frequency from 9 to 1 to simulate an inaccurate profile # FDATA: 1 _start #c# 1 _start #end_if_1# 0 1 end_if_1: # first uses of R14 and RBX appear at this point, possible move point for SW mov %r14, %rdi mov %rbx, %rdi leaq -0x20(%rbp), %r14 movq -0x20(%rbp), %rdi addq $0x20, %rsp pop %r14 pop %rbx pop %rbp ret .cfi_endproc .size _start, .-_start .data rel: .quad _start # CHECK: BOLT-INFO: Shrink wrapping moved 0 spills inserting load/stores and 0 spills inserting push/pops