diff options
| -rw-r--r-- | llvm/lib/Transforms/Scalar/CodeGenPrepare.cpp | 13 | ||||
| -rw-r--r-- | llvm/test/CodeGen/X86/opt-ext-uses.ll | 2 |
2 files changed, 11 insertions, 4 deletions
diff --git a/llvm/lib/Transforms/Scalar/CodeGenPrepare.cpp b/llvm/lib/Transforms/Scalar/CodeGenPrepare.cpp index 47e60cd74b4..8da09127e96 100644 --- a/llvm/lib/Transforms/Scalar/CodeGenPrepare.cpp +++ b/llvm/lib/Transforms/Scalar/CodeGenPrepare.cpp @@ -36,7 +36,7 @@ using namespace llvm; namespace { cl::opt<bool> OptExtUses("optimize-ext-uses", - cl::init(false), cl::Hidden); + cl::init(true), cl::Hidden); } namespace { @@ -929,6 +929,10 @@ bool CodeGenPrepare::OptimizeExtUses(Instruction *I) { if (Src->hasOneUse()) return false; + // Only do this xform is truncating is free. + if (!TLI->isTruncateFree(I->getType(), Src->getType())) + return false; + // Only safe to perform the optimization if the source is also defined in // this block. if (!isa<Instruction>(Src) || DefBB != cast<Instruction>(Src)->getParent()) @@ -952,8 +956,11 @@ bool CodeGenPrepare::OptimizeExtUses(Instruction *I) { for (Value::use_iterator UI = Src->use_begin(), E = Src->use_end(); UI != E; ++UI) { Instruction *User = cast<Instruction>(*UI); - if (User->getParent() == DefBB) continue; - if (isa<PHINode>(User)) + BasicBlock *UserBB = User->getParent(); + if (UserBB == DefBB) continue; + // Be conservative. We don't want this xform to end up introducing + // reloads just before load / store instructions. + if (isa<PHINode>(User) || isa<LoadInst>(User) || isa<StoreInst>(User)) return false; } diff --git a/llvm/test/CodeGen/X86/opt-ext-uses.ll b/llvm/test/CodeGen/X86/opt-ext-uses.ll index faa9be75504..322850c5523 100644 --- a/llvm/test/CodeGen/X86/opt-ext-uses.ll +++ b/llvm/test/CodeGen/X86/opt-ext-uses.ll @@ -1,4 +1,4 @@ -; RUN: llvm-as < %s | llc -march=x86 -optimize-ext-uses=true | grep movw | count 1 +; RUN: llvm-as < %s | llc -march=x86 | grep movw | count 1 define i16 @t() signext { entry: |
