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PGO: Add test case for branch weights and function call counts record…

…ing.
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michaelwoerister committed Nov 22, 2019
1 parent bd816fd commit 0675d65093e7173be676c07582085bf596ce966e
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# needs-profiler-support

-include ../tools.mk

# This test makes sure that instrumented binaries record the right counts for
# functions being called and branches being taken. We run an instrumented binary
# with an argument that causes a know path through the program and then check
# that the expected counts get added to the use-phase LLVM IR.

# LLVM doesn't support instrumenting binaries that use SEH:
# https://github.com/rust-lang/rust/issues/61002
#
# Things work fine with -Cpanic=abort though.
ifdef IS_MSVC
COMMON_FLAGS=-Cpanic=abort
endif

all:
# We don't compile `opaque` with either optimizations or instrumentation.
# We don't compile `opaque` with either optimizations or instrumentation.
$(RUSTC) $(COMMON_FLAGS) opaque.rs
# Compile the test program with instrumentation
mkdir -p "$(TMPDIR)"/prof_data_dir
$(RUSTC) $(COMMON_FLAGS) interesting.rs \
-Cprofile-generate="$(TMPDIR)"/prof_data_dir -O -Ccodegen-units=1
$(RUSTC) $(COMMON_FLAGS) main.rs -Cprofile-generate="$(TMPDIR)"/prof_data_dir -O
# The argument below generates to the expected branch weights
$(call RUN,main aaaaaaaaaaaa2bbbbbbbbbbbb2bbbbbbbbbbbbbbbbcc) || exit 1
"$(LLVM_BIN_DIR)"/llvm-profdata merge \
-o "$(TMPDIR)"/prof_data_dir/merged.profdata \
"$(TMPDIR)"/prof_data_dir
$(RUSTC) $(COMMON_FLAGS) interesting.rs \
-Cprofile-use="$(TMPDIR)"/prof_data_dir/merged.profdata -O \
-Ccodegen-units=1 --emit=llvm-ir
cat "$(TMPDIR)"/interesting.ll | "$(LLVM_FILECHECK)" filecheck-patterns.txt
@@ -0,0 +1,24 @@

# First, establish that certain !prof labels are attached to the expected
# functions and branching instructions.

CHECK: define void @function_called_twice(i32 %c) {{.*}} !prof !29 {
CHECK: br i1 {{.*}}, label {{.*}}, label {{.*}}, !prof !30

CHECK: define void @function_called_42_times(i32 %c) {{.*}} !prof !31 {
CHECK: switch i32 %c, label {{.*}} [
CHECK-NEXT: i32 97, label {{.*}}
CHECK-NEXT: i32 98, label {{.*}}
CHECK-NEXT: ], !prof !32

CHECK: define void @function_called_never(i32 {{.*}} !prof !33 {



# Now check that those !prof tags hold the expected counts

CHECK: !29 = !{!"function_entry_count", i64 2}
CHECK: !30 = !{!"branch_weights", i32 2, i32 0}
CHECK: !31 = !{!"function_entry_count", i64 42}
CHECK: !32 = !{!"branch_weights", i32 2, i32 12, i32 28}
CHECK: !33 = !{!"function_entry_count", i64 0}
@@ -0,0 +1,40 @@
#![crate_name="interesting"]
#![crate_type="rlib"]

extern crate opaque;

#[no_mangle]
#[inline(never)]
pub fn function_called_twice(c: char) {
if c == '2' {
// This branch is taken twice
opaque::f1();
} else {
// This branch is never taken
opaque::f2();
}
}

#[no_mangle]
#[inline(never)]
pub fn function_called_42_times(c: char) {
if c == 'a' {
// This branch is taken 12 times
opaque::f1();
} else {

if c == 'b' {
// This branch is taken 28 times
opaque::f2();
} else {
// This branch is taken 2 times
opaque::f3();
}
}
}

#[no_mangle]
#[inline(never)]
pub fn function_called_never(_: char) {
opaque::f1();
}
@@ -0,0 +1,17 @@
extern crate interesting;

fn main() {
let arg = std::env::args().skip(1).next().unwrap();

for c in arg.chars() {
if c == '2' {
interesting::function_called_twice(c);
} else {
interesting::function_called_42_times(c);
}

if c == '0' {
interesting::function_called_never(c);
}
}
}
@@ -0,0 +1,6 @@
#![crate_name="opaque"]
#![crate_type="rlib"]

pub fn f1() {}
pub fn f2() {}
pub fn f3() {}

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