From 56e3793acf8099eafa36154d2b6c900d46b5965e Mon Sep 17 00:00:00 2001 From: Cameron Zwarich Date: Wed, 2 Mar 2011 03:31:46 +0000 Subject: [PATCH] Eliminate the unused CodeGenPrepare option to split critical edges. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@126825 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Transforms/Scalar/CodeGenPrepare.cpp | 129 +----------------- test/CodeGen/ARM/code-placement.ll | 2 +- .../X86/2010-09-30-CMOV-JumpTable-PHI.ll | 2 +- 3 files changed, 3 insertions(+), 130 deletions(-) diff --git a/lib/Transforms/Scalar/CodeGenPrepare.cpp b/lib/Transforms/Scalar/CodeGenPrepare.cpp index 5d17e5f8d52..c90cb32b98b 100644 --- a/lib/Transforms/Scalar/CodeGenPrepare.cpp +++ b/lib/Transforms/Scalar/CodeGenPrepare.cpp @@ -58,11 +58,6 @@ STATISTIC(NumMemoryInsts, "Number of memory instructions whose address " STATISTIC(NumExtsMoved, "Number of [s|z]ext instructions combined with loads"); STATISTIC(NumExtUses, "Number of uses of [s|z]ext instructions optimized"); -static cl::opt -CriticalEdgeSplit("cgp-critical-edge-splitting", - cl::desc("Split critical edges during codegen prepare"), - cl::init(false), cl::Hidden); - namespace { class CodeGenPrepare : public FunctionPass { /// TLI - Keep a pointer of a TargetLowering to consult for determining @@ -144,11 +139,6 @@ bool CodeGenPrepare::runOnFunction(Function &F) { // unconditional branch. EverMadeChange |= EliminateMostlyEmptyBlocks(F); - // Now find loop back edges, but only if they are being used to decide which - // critical edges to split. - if (CriticalEdgeSplit) - findLoopBackEdges(F); - bool MadeChange = true; while (MadeChange) { MadeChange = false; @@ -350,110 +340,6 @@ void CodeGenPrepare::EliminateMostlyEmptyBlock(BasicBlock *BB) { DEBUG(dbgs() << "AFTER:\n" << *DestBB << "\n\n\n"); } -/// FindReusablePredBB - Check all of the predecessors of the block DestPHI -/// lives in to see if there is a block that we can reuse as a critical edge -/// from TIBB. -static BasicBlock *FindReusablePredBB(PHINode *DestPHI, BasicBlock *TIBB) { - BasicBlock *Dest = DestPHI->getParent(); - - /// TIPHIValues - This array is lazily computed to determine the values of - /// PHIs in Dest that TI would provide. - SmallVector TIPHIValues; - - /// TIBBEntryNo - This is a cache to speed up pred queries for TIBB. - unsigned TIBBEntryNo = 0; - - // Check to see if Dest has any blocks that can be used as a split edge for - // this terminator. - for (unsigned pi = 0, e = DestPHI->getNumIncomingValues(); pi != e; ++pi) { - BasicBlock *Pred = DestPHI->getIncomingBlock(pi); - // To be usable, the pred has to end with an uncond branch to the dest. - BranchInst *PredBr = dyn_cast(Pred->getTerminator()); - if (!PredBr || !PredBr->isUnconditional()) - continue; - // Must be empty other than the branch and debug info. - BasicBlock::iterator I = Pred->begin(); - while (isa(I)) - I++; - if (&*I != PredBr) - continue; - // Cannot be the entry block; its label does not get emitted. - if (Pred == &Dest->getParent()->getEntryBlock()) - continue; - - // Finally, since we know that Dest has phi nodes in it, we have to make - // sure that jumping to Pred will have the same effect as going to Dest in - // terms of PHI values. - PHINode *PN; - unsigned PHINo = 0; - unsigned PredEntryNo = pi; - - bool FoundMatch = true; - for (BasicBlock::iterator I = Dest->begin(); - (PN = dyn_cast(I)); ++I, ++PHINo) { - if (PHINo == TIPHIValues.size()) { - if (PN->getIncomingBlock(TIBBEntryNo) != TIBB) - TIBBEntryNo = PN->getBasicBlockIndex(TIBB); - TIPHIValues.push_back(PN->getIncomingValue(TIBBEntryNo)); - } - - // If the PHI entry doesn't work, we can't use this pred. - if (PN->getIncomingBlock(PredEntryNo) != Pred) - PredEntryNo = PN->getBasicBlockIndex(Pred); - - if (TIPHIValues[PHINo] != PN->getIncomingValue(PredEntryNo)) { - FoundMatch = false; - break; - } - } - - // If we found a workable predecessor, change TI to branch to Succ. - if (FoundMatch) - return Pred; - } - return 0; -} - - -/// SplitEdgeNicely - Split the critical edge from TI to its specified -/// successor if it will improve codegen. We only do this if the successor has -/// phi nodes (otherwise critical edges are ok). If there is already another -/// predecessor of the succ that is empty (and thus has no phi nodes), use it -/// instead of introducing a new block. -static void SplitEdgeNicely(TerminatorInst *TI, unsigned SuccNum, - SmallSet, 8> &BackEdges, - Pass *P) { - BasicBlock *TIBB = TI->getParent(); - BasicBlock *Dest = TI->getSuccessor(SuccNum); - assert(isa(Dest->begin()) && - "This should only be called if Dest has a PHI!"); - PHINode *DestPHI = cast(Dest->begin()); - - // Do not split edges to EH landing pads. - if (InvokeInst *Invoke = dyn_cast(TI)) - if (Invoke->getSuccessor(1) == Dest) - return; - - // As a hack, never split backedges of loops. Even though the copy for any - // PHIs inserted on the backedge would be dead for exits from the loop, we - // assume that the cost of *splitting* the backedge would be too high. - if (BackEdges.count(std::make_pair(TIBB, Dest))) - return; - - if (BasicBlock *ReuseBB = FindReusablePredBB(DestPHI, TIBB)) { - ProfileInfo *PFI = P->getAnalysisIfAvailable(); - if (PFI) - PFI->splitEdge(TIBB, Dest, ReuseBB); - Dest->removePredecessor(TIBB); - TI->setSuccessor(SuccNum, ReuseBB); - return; - } - - SplitCriticalEdge(TI, SuccNum, P, true); -} - - /// OptimizeNoopCopyExpression - If the specified cast instruction is a noop /// copy (e.g. it's casting from one pointer type to another, i32->i8 on PPC), /// sink it into user blocks to reduce the number of virtual @@ -1081,21 +967,8 @@ bool CodeGenPrepare::OptimizeInst(Instruction *I) { // across basic blocks and rewrite them to improve basic-block-at-a-time // selection. bool CodeGenPrepare::OptimizeBlock(BasicBlock &BB) { - bool MadeChange = false; - - // Split all critical edges where the dest block has a PHI. - if (CriticalEdgeSplit) { - TerminatorInst *BBTI = BB.getTerminator(); - if (BBTI->getNumSuccessors() > 1 && !isa(BBTI)) { - for (unsigned i = 0, e = BBTI->getNumSuccessors(); i != e; ++i) { - BasicBlock *SuccBB = BBTI->getSuccessor(i); - if (isa(SuccBB->begin()) && isCriticalEdge(BBTI, i, true)) - SplitEdgeNicely(BBTI, i, BackEdges, this); - } - } - } - SunkAddrs.clear(); + bool MadeChange = false; CurInstIterator = BB.begin(); for (BasicBlock::iterator E = BB.end(); CurInstIterator != E; ) diff --git a/test/CodeGen/ARM/code-placement.ll b/test/CodeGen/ARM/code-placement.ll index 845be8c20ea..036598fc060 100644 --- a/test/CodeGen/ARM/code-placement.ll +++ b/test/CodeGen/ARM/code-placement.ll @@ -1,4 +1,4 @@ -; RUN: llc < %s -mtriple=armv7-apple-darwin -cgp-critical-edge-splitting=0 | FileCheck %s +; RUN: llc < %s -mtriple=armv7-apple-darwin | FileCheck %s ; PHI elimination shouldn't break backedge. ; rdar://8263994 diff --git a/test/CodeGen/X86/2010-09-30-CMOV-JumpTable-PHI.ll b/test/CodeGen/X86/2010-09-30-CMOV-JumpTable-PHI.ll index cae81d086ea..73e996c5d55 100644 --- a/test/CodeGen/X86/2010-09-30-CMOV-JumpTable-PHI.ll +++ b/test/CodeGen/X86/2010-09-30-CMOV-JumpTable-PHI.ll @@ -1,4 +1,4 @@ -; RUN: llc -verify-machineinstrs -cgp-critical-edge-splitting=0 -mcpu=i386 < %s +; RUN: llc -verify-machineinstrs -mcpu=i386 < %s target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:32:32-n8:16:32" target triple = "i386-pc-linux-gnu"