From 1d35e9aebeb83b76b6f55d4f754736aa7321fae0 Mon Sep 17 00:00:00 2001 From: Duncan Sands Date: Sat, 4 Oct 2008 13:24:24 +0000 Subject: Ignore loads from and stores to local memory (i.e. allocas) when deciding whether to mark a function readnone/readonly. Since the pass is currently run before SROA, this may be quite helpful. Requested by Chris on IRC. llvm-svn: 57050 --- llvm/lib/Transforms/IPO/AddReadAttrs.cpp | 35 ++++++++++++++++++++++++-------- 1 file changed, 26 insertions(+), 9 deletions(-) (limited to 'llvm/lib/Transforms') diff --git a/llvm/lib/Transforms/IPO/AddReadAttrs.cpp b/llvm/lib/Transforms/IPO/AddReadAttrs.cpp index 7af071c40bd..5460a5bde7b 100644 --- a/llvm/lib/Transforms/IPO/AddReadAttrs.cpp +++ b/llvm/lib/Transforms/IPO/AddReadAttrs.cpp @@ -86,17 +86,34 @@ bool AddReadAttrs::runOnSCC(const std::vector &SCC) { // Scan the function body for instructions that may read or write memory. for (inst_iterator II = inst_begin(F), E = inst_end(F); II != E; ++II) { - CallSite CS = CallSite::get(&*II); - - // Ignore calls to functions in the same SCC. - if (CS.getInstruction() && SCCNodes.count(CG[CS.getCalledFunction()])) - continue; - - if (II->mayWriteToMemory()) + Instruction *I = &*II; + + // Some instructions can be ignored even if they read or write memory. + // Detect these now, skipping to the next instruction if one is found. + CallSite CS = CallSite::get(I); + if (CS.getInstruction()) { + // Ignore calls to functions in the same SCC. + if (SCCNodes.count(CG[CS.getCalledFunction()])) + continue; + } else if (LoadInst *LI = dyn_cast(I)) { + Value *Target = LI->getPointerOperand()->getUnderlyingObject(); + // Ignore loads from local memory. + if (isa(Target)) + continue; + } else if (StoreInst *SI = dyn_cast(I)) { + Value *Target = SI->getPointerOperand()->getUnderlyingObject(); + // Ignore stores to local memory. + if (isa(Target)) + continue; + } + + // Any remaining instructions need to be taken seriously! Check if they + // read or write memory. + if (I->mayWriteToMemory()) // Writes memory. Just give up. return false; - - ReadsMemory |= II->mayReadFromMemory(); + // If this instruction may read memory, remember that. + ReadsMemory |= I->mayReadFromMemory(); } } -- cgit v1.2.3