From c82b6a1ed2496ce0d61d2e51ed3a4cac4db786da Mon Sep 17 00:00:00 2001 From: Duncan Sands Date: Sat, 4 Oct 2008 13:24:24 +0000 Subject: [PATCH] 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. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@57050 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Transforms/IPO/AddReadAttrs.cpp | 31 ++++++++++++++----- .../AddReadAttrs/2008-10-04-LocalMemory.ll | 10 ++++++ 2 files changed, 34 insertions(+), 7 deletions(-) create mode 100644 test/Transforms/AddReadAttrs/2008-10-04-LocalMemory.ll diff --git a/lib/Transforms/IPO/AddReadAttrs.cpp b/lib/Transforms/IPO/AddReadAttrs.cpp index 7af071c40bd..5460a5bde7b 100644 --- a/lib/Transforms/IPO/AddReadAttrs.cpp +++ b/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); + Instruction *I = &*II; - // Ignore calls to functions in the same SCC. - if (CS.getInstruction() && SCCNodes.count(CG[CS.getCalledFunction()])) - continue; + // 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; + } - if (II->mayWriteToMemory()) + // 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(); } } diff --git a/test/Transforms/AddReadAttrs/2008-10-04-LocalMemory.ll b/test/Transforms/AddReadAttrs/2008-10-04-LocalMemory.ll new file mode 100644 index 00000000000..0f63c1a58be --- /dev/null +++ b/test/Transforms/AddReadAttrs/2008-10-04-LocalMemory.ll @@ -0,0 +1,10 @@ +; RUN: llvm-as < %s | opt -addreadattrs | llvm-dis | grep readnone | count 2 + +declare i32 @g(i32*) readnone + +define i32 @f() { + %x = alloca i32 ; [#uses=2] + store i32 0, i32* %x + %y = call i32 @g(i32* %x) ; [#uses=1] + ret i32 %y +}