From 07706e5506fb1bf494667e9fd16795b6c0b4d0fb Mon Sep 17 00:00:00 2001 From: Nadav Rotem Date: Fri, 12 Apr 2013 00:48:32 +0000 Subject: Add a flag to align all basic blocks in the function. When debugging performance regressions we often ask ourselves if the regression that we see is due to poor isel/sched/ra or due to some micro-architetural problem. When comparing two code sequences one good way to rule out front-end bottlenecks (and other the issues) is to force code alignment. This pass adds a flag that forces the alignment of all of the basic blocks in the program. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@179353 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/CodeGen/MachineBlockPlacement.cpp | 14 ++++++++++++++ 1 file changed, 14 insertions(+) (limited to 'lib') diff --git a/lib/CodeGen/MachineBlockPlacement.cpp b/lib/CodeGen/MachineBlockPlacement.cpp index cd948e2..774df81 100644 --- a/lib/CodeGen/MachineBlockPlacement.cpp +++ b/lib/CodeGen/MachineBlockPlacement.cpp @@ -39,6 +39,7 @@ #include "llvm/CodeGen/MachineLoopInfo.h" #include "llvm/CodeGen/MachineModuleInfo.h" #include "llvm/Support/Allocator.h" +#include "llvm/Support/CommandLine.h" #include "llvm/Support/Debug.h" #include "llvm/Target/TargetInstrInfo.h" #include "llvm/Target/TargetLowering.h" @@ -52,6 +53,11 @@ STATISTIC(CondBranchTakenFreq, STATISTIC(UncondBranchTakenFreq, "Potential frequency of taking unconditional branches"); +static cl::opt AlignAllBlock("align-all-blocks", + cl::desc("Force the alignment of all " + "blocks in the function."), + cl::init(0), cl::Hidden); + namespace { class BlockChain; /// \brief Type for our function-wide basic block -> block chain mapping. @@ -1083,6 +1089,14 @@ bool MachineBlockPlacement::runOnMachineFunction(MachineFunction &F) { TLI = F.getTarget().getTargetLowering(); assert(BlockToChain.empty()); + if (AlignAllBlock) { + // Align all of the blocks in the function to a specific alignment. + for (MachineFunction::iterator FI = F.begin(), FE = F.end(); + FI != FE; ++FI) + FI->setAlignment(AlignAllBlock); + return true; + } + buildCFGChains(F); BlockToChain.clear(); -- cgit v1.1