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AArch64: add backend option to reserve x18 (platform register)

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AAPCS64 says that it's up to the platform to specify whether x18 is
reserved, and a first step on that way is to add a flag controlling
it.

From: Andrew Turner <andrew@fubar.geek.nz>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226664 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Tim Northover 2015-01-21 15:43:31 +00:00
parent 47f47f5d2a
commit 004d725549
2 changed files with 15 additions and 10 deletions
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10
lib/Target/AArch64/AArch64RegisterInfo.cpp
View File

@ -33,6 +33,10 @@ using namespace llvm;
#define GET_REGINFO_TARGET_DESC
#include "AArch64GenRegisterInfo.inc"
static cl::opt<bool>
ReserveX18("aarch64-reserve-x18", cl::Hidden,
cl::desc("Reserve X18, making it unavailable as GPR"));
AArch64RegisterInfo::AArch64RegisterInfo(const AArch64InstrInfo *tii,
const AArch64Subtarget *sti)
: AArch64GenRegisterInfo(AArch64::LR), TII(tii), STI(sti) {}
@ -98,7 +102,7 @@ AArch64RegisterInfo::getReservedRegs(const MachineFunction &MF) const {
Reserved.set(AArch64::W29);
}
if (STI->isTargetDarwin()) {
if (STI->isTargetDarwin() || ReserveX18) {
Reserved.set(AArch64::X18); // Platform register
Reserved.set(AArch64::W18);
}
@ -125,7 +129,7 @@ bool AArch64RegisterInfo::isReservedReg(const MachineFunction &MF,
return true;
case AArch64::X18:
case AArch64::W18:
return STI->isTargetDarwin();
return STI->isTargetDarwin() || ReserveX18;
case AArch64::FP:
case AArch64::W29:
return TFI->hasFP(MF) || STI->isTargetDarwin();
@ -387,7 +391,7 @@ unsigned AArch64RegisterInfo::getRegPressureLimit(const TargetRegisterClass *RC,
case AArch64::GPR64commonRegClassID:
return 32 - 1 // XZR/SP
- (TFI->hasFP(MF) || STI->isTargetDarwin()) // FP
- STI->isTargetDarwin() // X18 reserved as platform register
- (STI->isTargetDarwin() || ReserveX18) // X18 reserved as platform register
- hasBasePointer(MF); // X19
case AArch64::FPR8RegClassID:
case AArch64::FPR16RegClassID:

15
test/CodeGen/AArch64/arm64-platform-reg.ll
View File

@ -1,4 +1,5 @@
; RUN: llc -mtriple=arm64-apple-ios -o - %s | FileCheck %s --check-prefix=CHECK-DARWIN
; RUN: llc -mtriple=arm64-apple-ios -o - %s | FileCheck %s --check-prefix=CHECK-RESERVE-X18
; RUN: llc -mtriple=arm64-freebsd-gnu -aarch64-reserve-x18 -o - %s | FileCheck %s --check-prefix=CHECK-RESERVE-X18
; RUN: llc -mtriple=arm64-linux-gnu -o - %s | FileCheck %s
; x18 is reserved as a platform register on Darwin but not on other
@ -16,11 +17,11 @@ define void @keep_live() {
; CHECK: ldr x18
; CHECK: str x18
; CHECK-DARWIN-NOT: ldr fp
; CHECK-DARWIN-NOT: ldr x18
; CHECK-DARWIN: Spill
; CHECK-DARWIN-NOT: ldr fp
; CHECK-DARWIN-NOT: ldr x18
; CHECK-DARWIN: ret
; CHECK-RESERVE-X18-NOT: ldr fp
; CHECK-RESERVE-X18-NOT: ldr x18
; CHECK-RESERVE-X18: Spill
; CHECK-RESERVE-X18-NOT: ldr fp
; CHECK-RESERVE-X18-NOT: ldr x18
; CHECK-RESERVE-X18: ret
ret void
}