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Flags for displaying only hot nodes in CFGPrinter graph 

Added two flags to omit uncommon or dead paths in the CFG graphs:
  -cfg-hide-unreachable-paths
  -cfg-hide-deoptimize-paths

The main purpose is performance analysis when such block are not
"interesting" from perspective of common path performance.

Reviewed By: apilipenko, davidxl

Differential Revision: https://reviews.llvm.org/D74346
This commit is contained in:
Kirill Naumov 2020-02-21 16:36:09 -08:00 committed by Artur Pilipenko
parent 3648370a79
commit e33c9bb245
3 changed files with 74 additions and 0 deletions
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5
llvm/include/llvm/Analysis/CFGPrinter.h
View File

@ -53,6 +53,9 @@ public:
template<>
struct DOTGraphTraits<const Function*> : public DefaultDOTGraphTraits {
// Cache for is hidden property
llvm::DenseMap <const BasicBlock *, bool> isHiddenBasicBlock;
DOTGraphTraits (bool isSimple=false) : DefaultDOTGraphTraits(isSimple) {}
static std::string getGraphName(const Function *F) {
@ -173,6 +176,8 @@ struct DOTGraphTraits<const Function*> : public DefaultDOTGraphTraits {
// profile count (due to scaling).
return ("label=\"W:" + Twine(Weight->getZExtValue()) + "\"").str();
}
bool isNodeHidden(const BasicBlock *Node);
void computeHiddenNodes(const Function *F);
};
} // End llvm namespace

36
llvm/lib/Analysis/CFGPrinter.cpp
View File

@ -17,11 +17,14 @@
//
//===----------------------------------------------------------------------===//
#include "llvm/ADT/PostOrderIterator.h"
#include "llvm/Analysis/CFGPrinter.h"
#include "llvm/InitializePasses.h"
#include "llvm/Pass.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/FileSystem.h"
#include <algorithm>
using namespace llvm;
static cl::opt<std::string> CFGFuncName(
@ -33,6 +36,12 @@ static cl::opt<std::string> CFGDotFilenamePrefix(
"cfg-dot-filename-prefix", cl::Hidden,
cl::desc("The prefix used for the CFG dot file names."));
static cl::opt<bool> HideUnreachablePaths("cfg-hide-unreachable-paths",
cl::init(false));
static cl::opt<bool> HideDeoptimizePaths("cfg-hide-deoptimize-paths",
cl::init(false));
namespace {
struct CFGViewerLegacyPass : public FunctionPass {
static char ID; // Pass identifcation, replacement for typeid
@ -200,3 +209,30 @@ FunctionPass *llvm::createCFGOnlyPrinterLegacyPassPass () {
return new CFGOnlyPrinterLegacyPass();
}
void DOTGraphTraits<const Function *>::computeHiddenNodes(const Function *F) {
auto evaluateBB = [&](const BasicBlock *Node) {
if (succ_begin(Node) == succ_end(Node)) {
const Instruction *TI = Node->getTerminator();
isHiddenBasicBlock[Node] =
(HideUnreachablePaths && isa<UnreachableInst>(TI)) ||
(HideDeoptimizePaths && Node->getTerminatingDeoptimizeCall());
return;
}
isHiddenBasicBlock[Node] = std::all_of(
succ_begin(Node), succ_end(Node),
[this](const BasicBlock *BB) { return isHiddenBasicBlock[BB]; });
};
/// The post order traversal iteration is done to know the status of
/// isHiddenBasicBlock for all the successors on the current BB.
for_each(po_begin(&F->getEntryBlock()), po_end(&F->getEntryBlock()),
evaluateBB);
}
bool DOTGraphTraits<const Function *>::isNodeHidden(const BasicBlock *Node) {
// If both restricting flags are false, all nodes are displayed.
if (!HideUnreachablePaths && !HideDeoptimizePaths)
return false;
if (isHiddenBasicBlock.find(Node) == isHiddenBasicBlock.end())
computeHiddenNodes(Node->getParent());
return isHiddenBasicBlock[Node];
}

33
llvm/test/Other/cfg_deopt_unreach.ll Normal file
View File

@ -0,0 +1,33 @@
; RUN: opt < %s -analyze -dot-cfg -cfg-hide-unreachable-paths -cfg-dot-filename-prefix=unreach 2>/dev/null
; RUN: FileCheck %s -input-file=unreach.callee.dot -check-prefix=UNREACH
; RUN: opt < %s -analyze -dot-cfg -cfg-hide-deoptimize-paths -cfg-dot-filename-prefix=deopt 2>/dev/null
; RUN: FileCheck %s -input-file=deopt.callee.dot -check-prefix=DEOPT
; RUN: opt < %s -analyze -dot-cfg -cfg-dot-filename-prefix=no-flags 2>/dev/null
; RUN: FileCheck %s -input-file=no-flags.callee.dot -check-prefix=NO-FLAGS
; RUN: opt < %s -analyze -dot-cfg -cfg-hide-unreachable-paths -cfg-hide-deoptimize-paths -cfg-dot-filename-prefix=both-flags 2>/dev/null
; RUN: FileCheck %s -input-file=both-flags.callee.dot -check-prefix=BOTH-FLAGS
declare i8 @llvm.experimental.deoptimize.i8(...)
define i8 @callee(i1* %c) alwaysinline {
; NO-FLAGS: [shape=record,label="{%0:\l %c0 = load volatile i1, i1* %c\l br i1 %c0, label %lleft, label %lright\l|{<s0>T|<s1>F}}"];
; DEOPT: [shape=record,label="{%0:\l %c0 = load volatile i1, i1* %c\l br i1 %c0, label %lleft, label %lright\l|{<s0>T|<s1>F}}"];
; UNREACH: [shape=record,label="{%0:\l %c0 = load volatile i1, i1* %c\l br i1 %c0, label %lleft, label %lright\l|{<s0>T|<s1>F}}"];
; BOTH-FLAGS-NOT: [shape=record,label="{%0:\l %c0 = load volatile i1, i1* %c\l br i1 %c0, label %lleft, label %lright\l|{<s0>T|<s1>F}}"];
%c0 = load volatile i1, i1* %c
br i1 %c0, label %lleft, label %lright
; NO-FLAGS: [shape=record,label="{lleft: \l %v0 = call i8 (...) @llvm.experimental.deoptimize.i8(i32 1) [ \"deopt\"(i32 1)\l... ]\l ret i8 %v0\l}"];
; DEOPT-NOT: [shape=record,label="{lleft: \l %v0 = call i8 (...) @llvm.experimental.deoptimize.i8(i32 1) [ \"deopt\"(i32 1)\l... ]\l ret i8 %v0\l}"];
; UNREACH: [shape=record,label="{lleft: \l %v0 = call i8 (...) @llvm.experimental.deoptimize.i8(i32 1) [ \"deopt\"(i32 1)\l... ]\l ret i8 %v0\l}"];
; BOTH-FLAGS-NOT: [shape=record,label="{lleft: \l %v0 = call i8 (...) @llvm.experimental.deoptimize.i8(i32 1) [ \"deopt\"(i32 1)\l... ]\l ret i8 %v0\l}"];
lleft:
%v0 = call i8(...) @llvm.experimental.deoptimize.i8(i32 1) [ "deopt"(i32 1) ]
ret i8 %v0
; NO-FLAGS: [shape=record,label="{lright: \l unreachable\l}"];
; DEOPT: [shape=record,label="{lright: \l unreachable\l}"];
; UNREACH-NOT: [shape=record,label="{lright: \l unreachable\l}"];
; BOTH-FLAGS-NOT: [shape=record,label="{lright: \l unreachable\l}"];
lright:
unreachable
}