Index: llvm/trunk/include/llvm/CodeGen/TargetFrameLowering.h =================================================================== --- llvm/trunk/include/llvm/CodeGen/TargetFrameLowering.h +++ llvm/trunk/include/llvm/CodeGen/TargetFrameLowering.h @@ -378,6 +378,11 @@ return true; } + /// Check if the no-CSR optimisation is profitable for the given function. + virtual bool isProfitableForNoCSROpt(const Function &F) const { + return true; + } + /// Return initial CFA offset value i.e. the one valid at the beginning of the /// function (before any stack operations). virtual int getInitialCFAOffset(const MachineFunction &MF) const; Index: llvm/trunk/lib/CodeGen/RegUsageInfoCollector.cpp =================================================================== --- llvm/trunk/lib/CodeGen/RegUsageInfoCollector.cpp +++ llvm/trunk/lib/CodeGen/RegUsageInfoCollector.cpp @@ -171,7 +171,8 @@ SetRegAsDefined(PReg); } - if (TargetFrameLowering::isSafeForNoCSROpt(F)) { + if (TargetFrameLowering::isSafeForNoCSROpt(F) && + MF.getSubtarget().getFrameLowering()->isProfitableForNoCSROpt(F)) { ++NumCSROpt; LLVM_DEBUG(dbgs() << MF.getName() << " function optimized for not having CSR.\n"); Index: llvm/trunk/lib/CodeGen/TargetFrameLoweringImpl.cpp =================================================================== --- llvm/trunk/lib/CodeGen/TargetFrameLoweringImpl.cpp +++ llvm/trunk/lib/CodeGen/TargetFrameLoweringImpl.cpp @@ -71,7 +71,9 @@ // When interprocedural register allocation is enabled caller saved registers // are preferred over callee saved registers. - if (MF.getTarget().Options.EnableIPRA && isSafeForNoCSROpt(MF.getFunction())) + if (MF.getTarget().Options.EnableIPRA && + isSafeForNoCSROpt(MF.getFunction()) && + isProfitableForNoCSROpt(MF.getFunction())) return; // Get the callee saved register list... Index: llvm/trunk/lib/Target/ARM/ARMFrameLowering.h =================================================================== --- llvm/trunk/lib/Target/ARM/ARMFrameLowering.h +++ llvm/trunk/lib/Target/ARM/ARMFrameLowering.h @@ -63,6 +63,11 @@ bool enableShrinkWrapping(const MachineFunction &MF) const override { return true; } + bool isProfitableForNoCSROpt(const Function &F) const override { + // The no-CSR optimisation is bad for code size on ARM, because we can save + // many registers with a single PUSH/POP pair. + return false; + } private: void emitPushInst(MachineBasicBlock &MBB, MachineBasicBlock::iterator MI, Index: llvm/trunk/test/CodeGen/ARM/ipra-no-csr.ll =================================================================== --- llvm/trunk/test/CodeGen/ARM/ipra-no-csr.ll +++ llvm/trunk/test/CodeGen/ARM/ipra-no-csr.ll @@ -0,0 +1,22 @@ +; RUN: llc -mtriple armv7a--none-eabi < %s | FileCheck %s +; RUN: llc -mtriple armv7a--none-eabi < %s -enable-ipra | FileCheck %s + +; Other targets disable callee-saved registers for internal functions when +; using IPRA, but that isn't profitable for ARM because the PUSH/POP +; instructions can more efficiently save registers than using individual +; LDR/STRs in the caller. + +define internal void @callee() norecurse { +; CHECK-LABEL: callee: +entry: +; CHECK: push {r4, lr} +; CHECK: pop {r4, pc} + tail call void asm sideeffect "", "~{r4}"() + ret void +} + +define void @caller() { +entry: + call void @callee() + ret void +}