Index: include/llvm/CodeGen/MachineRegisterInfo.h =================================================================== --- include/llvm/CodeGen/MachineRegisterInfo.h +++ include/llvm/CodeGen/MachineRegisterInfo.h @@ -581,6 +581,9 @@ /// function. Writing to a constant register has no effect. bool isConstantPhysReg(unsigned PhysReg) const; + /// Returns true if PhysReg is always preserved by the caller. + bool isCallerPreservedPhysReg(unsigned PhysReg) const; + /// Get an iterator over the pressure sets affected by the given physical or /// virtual register. If RegUnit is physical, it must be a register unit (from /// MCRegUnitIterator). Index: include/llvm/Target/TargetRegisterInfo.h =================================================================== --- include/llvm/Target/TargetRegisterInfo.h +++ include/llvm/Target/TargetRegisterInfo.h @@ -497,6 +497,13 @@ /// function. Used by MachineRegisterInfo::isConstantPhysReg(). virtual bool isConstantPhysReg(unsigned PhysReg) const { return false; } + /// Returns true if PhysReg is always caller saved. + /// Used by MachineRegisterInfo::isCallerPreservedPhysReg(). + virtual bool isCallerPreservedPhysReg(unsigned PhysReg, + const MachineFunction &MF) const { + return false; + } + /// Prior to adding the live-out mask to a stackmap or patchpoint /// instruction, provide the target the opportunity to adjust it (mainly to /// remove pseudo-registers that should be ignored). Index: lib/CodeGen/MachineLICM.cpp =================================================================== --- lib/CodeGen/MachineLICM.cpp +++ lib/CodeGen/MachineLICM.cpp @@ -892,6 +892,10 @@ // Don't hoist an instruction that uses or defines a physical register. if (TargetRegisterInfo::isPhysicalRegister(Reg)) { if (MO.isUse()) { + // If the physreg is known to always be caller saved/restored then + // this use is safe to hoist + if (MRI->isCallerPreservedPhysReg(Reg)) + continue; // If the physreg has no defs anywhere, it's just an ambient register // and we can freely move its uses. Alternatively, if it's allocatable, // it could get allocated to something with a def during allocation. Index: lib/CodeGen/MachineRegisterInfo.cpp =================================================================== --- lib/CodeGen/MachineRegisterInfo.cpp +++ lib/CodeGen/MachineRegisterInfo.cpp @@ -487,6 +487,11 @@ return true; } +bool MachineRegisterInfo::isCallerPreservedPhysReg(unsigned PhysReg) const { + assert(TargetRegisterInfo::isPhysicalRegister(PhysReg)); + return getTargetRegisterInfo()->isCallerPreservedPhysReg(PhysReg, *MF); +} + /// markUsesInDebugValueAsUndef - Mark every DBG_VALUE referencing the /// specified register as undefined which causes the DBG_VALUE to be /// deleted during LiveDebugVariables analysis. Index: lib/Target/PowerPC/PPCRegisterInfo.h =================================================================== --- lib/Target/PowerPC/PPCRegisterInfo.h +++ lib/Target/PowerPC/PPCRegisterInfo.h @@ -83,6 +83,7 @@ void adjustStackMapLiveOutMask(uint32_t *Mask) const override; BitVector getReservedRegs(const MachineFunction &MF) const override; + bool isCallerPreservedPhysReg(unsigned PhysReg, const MachineFunction &MF) const override; /// We require the register scavenger. bool requiresRegisterScavenging(const MachineFunction &MF) const override { Index: lib/Target/PowerPC/PPCRegisterInfo.cpp =================================================================== --- lib/Target/PowerPC/PPCRegisterInfo.cpp +++ lib/Target/PowerPC/PPCRegisterInfo.cpp @@ -273,6 +273,19 @@ return Reserved; } +bool PPCRegisterInfo::isCallerPreservedPhysReg(unsigned PhysReg, + const MachineFunction &MF) const { + if (TM.isELFv2ABI() && PhysReg == PPC::X2) { + // X2 is guaranteed to be preserved within a function if it is reserved. + // The reason it's reserved is that it's the TOC pointer (and the function + // uses the TOC). In functions where it isn't reserved (i.e. leaf functions + // with no TOC access), we can't claim that it is preserved. + return (getReservedRegs(MF).test(PPC::X2)); + } else { + return false; + } +} + unsigned PPCRegisterInfo::getRegPressureLimit(const TargetRegisterClass *RC, MachineFunction &MF) const { const PPCFrameLowering *TFI = getFrameLowering(MF); Index: test/CodeGen/PowerPC/licm-tocReg.ll =================================================================== --- /dev/null +++ test/CodeGen/PowerPC/licm-tocReg.ll @@ -0,0 +1,51 @@ +; RUN: llc -verify-machineinstrs -mtriple=powerpc64le-unknown-linux-gnu < %s | FileCheck %s + +@ga = external global i32, align 4 +@gb = external global i32, align 4 + +; Function Attrs: nounwind +define signext i32 @test(i32 (i32)* nocapture %FP) local_unnamed_addr #0 { +; CHECK-LABEL: test: +; CHECK: # BB#0: # %entry +; CHECK-NEXT: addis 4, 2, .LC0@toc@ha +; CHECK-NEXT: addis 5, 2, .LC1@toc@ha +; CHECK-NEXT: ld 4, .LC0@toc@l(4) +; CHECK-NEXT: ld 5, .LC1@toc@l(5) +; CHECK-NEXT: lwz 6, 0(4) +; CHECK-NEXT: lwz 5, 0(5) +; CHECK-NEXT: cmpw 6, 5 +; CHECK-NEXT: lwz 5, 0(4) +; CHECK-NEXT: mr 4, 3 +; CHECK-NEXT: bgt 0, .LBB0_3 +; CHECK-NEXT: # BB#1: +; CHECK-NEXT: addis 3, 2, .LC0@toc@ha +; CHECK-NEXT: addis 6, 2, .LC1@toc@ha +; CHECK-NEXT: ld 3, .LC0@toc@l(3) +; CHECK-NEXT: ld 6, .LC1@toc@l(6) +; CHECK-NEXT: .p2align 5 +; CHECK-NEXT: .LBB0_2: # %if.end +; CHECK-NOT: addis {{[0-9]+}}, 2, .LC0@toc@ha +; CHECK-NOT: addis {{[0-9]+}}, 2, .LC1@toc@ha +; CHECK: blr +entry: + %0 = load volatile i32, i32* @ga, align 4 + %1 = load volatile i32, i32* @gb, align 4 + %cmp1 = icmp sgt i32 %0, %1 + %2 = load volatile i32, i32* @ga, align 4 + br i1 %cmp1, label %if.then, label %if.end + +if.then: ; preds = %if.end, %entry + %.lcssa = phi i32 [ %2, %entry ], [ %6, %if.end ] + %call = tail call signext i32 %FP(i32 signext %.lcssa) #1 + ret i32 %call + +if.end: ; preds = %entry, %if.end + %3 = phi i32 [ %6, %if.end ], [ %2, %entry ] + %inc = add nsw i32 %3, 1 + store volatile i32 %inc, i32* @ga, align 4 + %4 = load volatile i32, i32* @ga, align 4 + %5 = load volatile i32, i32* @gb, align 4 + %cmp = icmp sgt i32 %4, %5 + %6 = load volatile i32, i32* @ga, align 4 + br i1 %cmp, label %if.then, label %if.end +}