[llvm] [Propeller] CFG drift detect (PR #80431)
via llvm-commits
llvm-commits at lists.llvm.org
Fri Feb 2 05:17:12 PST 2024
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-backend-x86
Author: None (lifengxiang1025)
<details>
<summary>Changes</summary>
Now Propeller only detect code drift when using pgo together. This patch aims to add the ability to detect cfg drift.
---
Full diff: https://github.com/llvm/llvm-project/pull/80431.diff
3 Files Affected:
- (modified) llvm/include/llvm/CodeGen/MachineBasicBlock.h (+1-1)
- (modified) llvm/lib/CodeGen/BasicBlockSections.cpp (+53)
- (added) llvm/test/CodeGen/X86/basic-block-sections-cfg-drift-detect.ll (+67)
``````````diff
diff --git a/llvm/include/llvm/CodeGen/MachineBasicBlock.h b/llvm/include/llvm/CodeGen/MachineBasicBlock.h
index dc2035fa598c4..c3d8f14313d0f 100644
--- a/llvm/include/llvm/CodeGen/MachineBasicBlock.h
+++ b/llvm/include/llvm/CodeGen/MachineBasicBlock.h
@@ -659,7 +659,7 @@ class MachineBasicBlock
/// Sets the fixed BBID of this basic block.
void setBBID(const UniqueBBID &V) {
- assert(!BBID.has_value() && "Cannot change BBID.");
+ assert((!BBID.has_value() || BBID->BaseID == 0) && "Cannot change BBID.");
BBID = V;
}
diff --git a/llvm/lib/CodeGen/BasicBlockSections.cpp b/llvm/lib/CodeGen/BasicBlockSections.cpp
index eb3f9e7078f1a..4ca278f405d54 100644
--- a/llvm/lib/CodeGen/BasicBlockSections.cpp
+++ b/llvm/lib/CodeGen/BasicBlockSections.cpp
@@ -79,6 +79,8 @@
#include "llvm/InitializePasses.h"
#include "llvm/Target/TargetMachine.h"
#include <optional>
+#include <queue>
+#include <unordered_set>
using namespace llvm;
@@ -97,6 +99,17 @@ static cl::opt<bool> BBSectionsDetectSourceDrift(
"mismatch for this function"),
cl::init(true), cl::Hidden);
+static cl::opt<bool> BBSectionsDetectCFGDrift(
+ "bbsections-detect-cfg-drift",
+ cl::desc("This checks if function's cfg hash mismatch "
+ "with cfg hash recorded in profile"),
+ cl::init(false), cl::Hidden);
+
+static cl::opt<bool>
+ FirstMBBContainCFGHash("first-mbb-contain-cfg-hash",
+ cl::desc("Use cfg hash as first mbb base id"),
+ cl::init(false), cl::Hidden);
+
namespace {
class BasicBlockSections : public MachineFunctionPass {
@@ -284,9 +297,44 @@ bool llvm::hasInstrProfHashMismatch(MachineFunction &MF) {
return false;
}
+static uint64_t getCFGMD5(MachineFunction &MF) {
+ std::unordered_set<MachineBasicBlock *> Visited;
+ MD5 Hash;
+ std::queue<MachineBasicBlock *> Q;
+ if (!MF.empty()) {
+ Q.push(&*MF.begin());
+ Visited.insert(&*MF.begin());
+ }
+ while (!Q.empty()) {
+ MachineBasicBlock *Now = Q.front();
+ Q.pop();
+ using namespace llvm::support;
+ uint64_t Value = endian::byte_swap<uint32_t, llvm::endianness::little>(
+ Now->getBBID()->BaseID);
+ Hash.update(llvm::ArrayRef((uint8_t *)&Value, sizeof(Value)));
+ for (auto Iter = Now->succ_begin(); Iter != Now->succ_end(); Iter++) {
+ if (Visited.count(&**Iter)) {
+ continue;
+ }
+ Q.push(&**Iter);
+ Visited.insert(&**Iter);
+ }
+ }
+ llvm::MD5::MD5Result Result;
+ Hash.final(Result);
+ return Result.low();
+}
+
// Identify, arrange, and modify basic blocks which need separate sections
// according to the specification provided by the -fbasic-block-sections flag.
bool BasicBlockSections::handleBBSections(MachineFunction &MF) {
+ unsigned CFGHash = 0;
+ if (BBSectionsDetectCFGDrift) {
+ CFGHash = static_cast<unsigned>(getCFGMD5(MF));
+ if (FirstMBBContainCFGHash)
+ MF.begin()->setBBID({CFGHash, 0});
+ }
+
auto BBSectionsType = MF.getTarget().getBBSectionsType();
if (BBSectionsType == BasicBlockSection::None)
return false;
@@ -316,6 +364,11 @@ bool BasicBlockSections::handleBBSections(MachineFunction &MF) {
.getClusterInfoForFunction(MF.getName());
if (!HasProfile)
return false;
+ // Check for cfg drift.
+ if (BBSectionsDetectCFGDrift &&
+ ClusterInfo.begin()->BBID.BaseID != CFGHash) {
+ return false;
+ }
for (auto &BBClusterInfo : ClusterInfo) {
FuncClusterInfo.try_emplace(BBClusterInfo.BBID, BBClusterInfo);
}
diff --git a/llvm/test/CodeGen/X86/basic-block-sections-cfg-drift-detect.ll b/llvm/test/CodeGen/X86/basic-block-sections-cfg-drift-detect.ll
new file mode 100644
index 0000000000000..4e44c0bc6128a
--- /dev/null
+++ b/llvm/test/CodeGen/X86/basic-block-sections-cfg-drift-detect.ll
@@ -0,0 +1,67 @@
+; RUN: llc < %s -O0 -mtriple=x86_64-pc-linux -function-sections -basic-block-sections=labels -first-mbb-contain-cfg-hash=true -bbsections-detect-cfg-drift=true | FileCheck %s -check-prefix=HASH
+
+; RUN: echo '!_Z3fooi' > %t1
+; RUN: echo '!!2561660837 2' >> %t1
+; RUN: echo '!!1' >> %t1
+; RUN: llc < %s -O0 -mtriple=x86_64-pc-linux -function-sections -basic-block-sections=%t1 -first-mbb-contain-cfg-hash=true -bbsections-detect-cfg-drift=true | FileCheck %s -check-prefix=MATCH
+
+; RUN: echo '!_Z3fooi' > %t1
+; RUN: echo '!!11111111 2' >> %t1
+; RUN: echo '!!1' >> %t1
+; RUN: llc < %s -O0 -mtriple=x86_64-pc-linux -function-sections -basic-block-sections=%t1 -first-mbb-contain-cfg-hash=true -bbsections-detect-cfg-drift=true | FileCheck %s -check-prefix=MISMATCH
+
+; HASH: .ascii "\245\257\277\305\t" # BB id
+; MATCH: callq _Z3bazi at PLT
+; MATCH: callq _Z3bari at PLT
+; MISMATCH: callq _Z3bari at PLT
+; MISMATCH: callq _Z3bazi at PLT
+
+; ModuleID = 'foo.cc'
+source_filename = "foo.cc"
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+; Function Attrs: mustprogress noinline optnone uwtable
+define dso_local noundef i32 @_Z3fooi(i32 noundef %a) #0 {
+entry:
+ %retval = alloca i32, align 4
+ %a.addr = alloca i32, align 4
+ store i32 %a, ptr %a.addr, align 4
+ %0 = load i32, ptr %a.addr, align 4
+ %and = and i32 %0, 1
+ %tobool = icmp ne i32 %and, 0
+ br i1 %tobool, label %if.then, label %if.end
+
+if.then: ; preds = %entry
+ %1 = load i32, ptr %a.addr, align 4
+ %call = call noundef i32 @_Z3bari(i32 noundef %1)
+ store i32 %call, ptr %retval, align 4
+ br label %return
+
+if.end: ; preds = %entry
+ %2 = load i32, ptr %a.addr, align 4
+ %call1 = call noundef i32 @_Z3bazi(i32 noundef %2)
+ store i32 %call1, ptr %retval, align 4
+ br label %return
+
+return: ; preds = %if.end, %if.then
+ %3 = load i32, ptr %retval, align 4
+ ret i32 %3
+}
+
+declare noundef i32 @_Z3bari(i32 noundef) #1
+
+declare noundef i32 @_Z3bazi(i32 noundef) #1
+
+attributes #0 = { mustprogress noinline optnone uwtable "frame-pointer"="all" "min-legal-vector-width"="0" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+cmov,+cx8,+fxsr,+mmx,+sse,+sse2,+x87" "tune-cpu"="generic" }
+attributes #1 = { "frame-pointer"="all" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+cmov,+cx8,+fxsr,+mmx,+sse,+sse2,+x87" "tune-cpu"="generic" }
+
+!llvm.module.flags = !{!0, !1, !2, !3, !4}
+!llvm.ident = !{!5}
+
+!0 = !{i32 1, !"wchar_size", i32 4}
+!1 = !{i32 8, !"PIC Level", i32 2}
+!2 = !{i32 7, !"PIE Level", i32 2}
+!3 = !{i32 7, !"uwtable", i32 2}
+!4 = !{i32 7, !"frame-pointer", i32 2}
+!5 = !{!"clang version 18.0.0"}
``````````
</details>
https://github.com/llvm/llvm-project/pull/80431
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