Add an option to disable codegen prepare critical edge splitting. In theory, PHI elimination is already doing all (most?) of the splitting needed. But machine-licm and machine-sink seem to miss some important optimizations when splitting is disabled.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@111224 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Scalar/CodeGenPrepare.cpp b/lib/Transforms/Scalar/CodeGenPrepare.cpp
index 823cace..a4fcf63 100644
--- a/lib/Transforms/Scalar/CodeGenPrepare.cpp
+++ b/lib/Transforms/Scalar/CodeGenPrepare.cpp
@@ -33,6 +33,7 @@
#include "llvm/ADT/SmallSet.h"
#include "llvm/Assembly/Writer.h"
#include "llvm/Support/CallSite.h"
+#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/GetElementPtrTypeIterator.h"
#include "llvm/Support/PatternMatch.h"
@@ -41,6 +42,11 @@
using namespace llvm;
using namespace llvm::PatternMatch;
+static cl::opt<bool>
+CriticalEdgeSplit("cgp-critical-edge-splitting",
+ cl::desc("Split critical edges during codegen prepare"),
+ cl::init(true), cl::Hidden);
+
namespace {
class CodeGenPrepare : public FunctionPass {
/// TLI - Keep a pointer of a TargetLowering to consult for determining
@@ -891,12 +897,14 @@
bool MadeChange = false;
// Split all critical edges where the dest block has a PHI.
- TerminatorInst *BBTI = BB.getTerminator();
- if (BBTI->getNumSuccessors() > 1 && !isa<IndirectBrInst>(BBTI)) {
- for (unsigned i = 0, e = BBTI->getNumSuccessors(); i != e; ++i) {
- BasicBlock *SuccBB = BBTI->getSuccessor(i);
- if (isa<PHINode>(SuccBB->begin()) && isCriticalEdge(BBTI, i, true))
- SplitEdgeNicely(BBTI, i, BackEdges, this);
+ if (CriticalEdgeSplit) {
+ TerminatorInst *BBTI = BB.getTerminator();
+ if (BBTI->getNumSuccessors() > 1 && !isa<IndirectBrInst>(BBTI)) {
+ for (unsigned i = 0, e = BBTI->getNumSuccessors(); i != e; ++i) {
+ BasicBlock *SuccBB = BBTI->getSuccessor(i);
+ if (isa<PHINode>(SuccBB->begin()) && isCriticalEdge(BBTI, i, true))
+ SplitEdgeNicely(BBTI, i, BackEdges, this);
+ }
}
}