From 38d945872097549606ea62b64ded743afdab0648 Mon Sep 17 00:00:00 2001 From: Bill Schmidt Date: Wed, 10 Oct 2012 20:54:15 +0000 Subject: [PATCH] The PowerPC VRSAVE register has been somewhat of an odd beast since the Altivec extensions were introduced. Its use is optional, and allows the compiler to communicate to the operating system which vector registers should be saved and restored during a context switch. In practice, this information is ignored by the various operating systems using the SVR4 ABI; the kernel saves and restores the entire register state. Setting the VRSAVE register is no longer performed by the AIX XL compilers, the IBM i compilers, or by GCC on Power Linux systems. It seems best to avoid this logic within LLVM as well. This patch avoids generating code to update and restore VRSAVE for the PowerPC SVR4 ABIs (32- and 64-bit). The code remains in place for the Darwin ABI. llvm-svn: 165656 --- llvm/lib/Target/PowerPC/PPCFrameLowering.cpp | 16 +++++++++++----- llvm/lib/Target/PowerPC/PPCISelDAGToDAG.cpp | 4 +++- llvm/test/CodeGen/PowerPC/novrsave.ll | 15 +++++++++++++++ 3 files changed, 29 insertions(+), 6 deletions(-) create mode 100644 llvm/test/CodeGen/PowerPC/novrsave.ll diff --git a/llvm/lib/Target/PowerPC/PPCFrameLowering.cpp b/llvm/lib/Target/PowerPC/PPCFrameLowering.cpp index b1c02e5..caf7bf2 100644 --- a/llvm/lib/Target/PowerPC/PPCFrameLowering.cpp +++ b/llvm/lib/Target/PowerPC/PPCFrameLowering.cpp @@ -50,6 +50,11 @@ static const uint16_t VRRegNo[] = { /// to manipulate the VRSAVE register, even though it uses vector registers. /// This can happen when the only registers used are known to be live in or out /// of the function. Remove all of the VRSAVE related code from the function. +/// FIXME: The removal of the code results in a compile failure at -O0 when the +/// function contains a function call, as the GPR containing original VRSAVE +/// contents is spilled and reloaded around the call. Without the prolog code, +/// the spill instruction refers to an undefined register. This code needs +/// to account for all uses of that GPR. static void RemoveVRSaveCode(MachineInstr *MI) { MachineBasicBlock *Entry = MI->getParent(); MachineFunction *MF = Entry->getParent(); @@ -283,12 +288,13 @@ void PPCFrameLowering::emitPrologue(MachineFunction &MF) const { // Scan the prolog, looking for an UPDATE_VRSAVE instruction. If we find it, // process it. - for (unsigned i = 0; MBBI != MBB.end(); ++i, ++MBBI) { - if (MBBI->getOpcode() == PPC::UPDATE_VRSAVE) { - HandleVRSaveUpdate(MBBI, TII); - break; + if (!Subtarget.isSVR4ABI()) + for (unsigned i = 0; MBBI != MBB.end(); ++i, ++MBBI) { + if (MBBI->getOpcode() == PPC::UPDATE_VRSAVE) { + HandleVRSaveUpdate(MBBI, TII); + break; + } } - } // Move MBBI back to the beginning of the function. MBBI = MBB.begin(); diff --git a/llvm/lib/Target/PowerPC/PPCISelDAGToDAG.cpp b/llvm/lib/Target/PowerPC/PPCISelDAGToDAG.cpp index b52452c..6195441 100644 --- a/llvm/lib/Target/PowerPC/PPCISelDAGToDAG.cpp +++ b/llvm/lib/Target/PowerPC/PPCISelDAGToDAG.cpp @@ -53,7 +53,9 @@ namespace { GlobalBaseReg = 0; SelectionDAGISel::runOnMachineFunction(MF); - InsertVRSaveCode(MF); + if (!PPCSubTarget.isSVR4ABI()) + InsertVRSaveCode(MF); + return true; } diff --git a/llvm/test/CodeGen/PowerPC/novrsave.ll b/llvm/test/CodeGen/PowerPC/novrsave.ll new file mode 100644 index 0000000..a70576a --- /dev/null +++ b/llvm/test/CodeGen/PowerPC/novrsave.ll @@ -0,0 +1,15 @@ +; RUN: llc -O0 -mtriple=powerpc-unknown-linux-gnu < %s | FileCheck %s +; RUN: llc -O0 -mtriple=powerpc64-unknown-linux-gnu < %s | FileCheck %s + +; This verifies that the code to update VRSAVE has been removed for SVR4. + +define <4 x float> @bar(<4 x float> %v) nounwind { +entry: + %v.addr = alloca <4 x float>, align 16 + store <4 x float> %v, <4 x float>* %v.addr, align 16 + %0 = load <4 x float>* %v.addr, align 16 + ret <4 x float> %0 +} + +; CHECK-NOT: mfspr +; CHECK-NOT: mtspr -- 2.7.4