[AArch64] Add support for -ffixed-x30

Add support for reserving LR in:

* the driver through `-ffixed-x30`
* cc1 through `-target-feature +reserve-x30`
* the backend through `-mattr=+reserve-x30`
* a subtarget feature `reserve-x30`

the same way we're doing for the other registers.

Author: francisvm

clang/lib/Driver/ToolChains/Arch/AArch64.cpp

@@ -409,6 +409,9 @@ void aarch64::getAArch64TargetFeatures(const Driver &D,
   if (Args.hasArg(options::OPT_ffixed_x28))
     Features.push_back("+reserve-x28");
 
+  if (Args.hasArg(options::OPT_ffixed_x30))
+    Features.push_back("+reserve-x30");
+
   if (Args.hasArg(options::OPT_fcall_saved_x8))
     Features.push_back("+call-saved-x8");
 

clang/test/Driver/aarch64-fixed-x-register.c

@@ -94,6 +94,10 @@
 // RUN: FileCheck --check-prefix=CHECK-FIXED-X28 < %t %s
 // CHECK-FIXED-X28: "-target-feature" "+reserve-x28"
 
+// RUN: %clang -target aarch64-none-gnu -ffixed-x30 -### %s 2> %t
+// RUN: FileCheck --check-prefix=CHECK-FIXED-X30 < %t %s
+// CHECK-FIXED-X30: "-target-feature" "+reserve-x30"
+
 // Test multiple of reserve-x# options together.
 // RUN: %clang -target aarch64-none-gnu \
 // RUN: -ffixed-x1 \

llvm/lib/Target/AArch64/AArch64.td

@@ -142,7 +142,7 @@ def FeatureStrictAlign : SubtargetFeature<"strict-align",
                                           "Disallow all unaligned memory "
                                           "access">;
 
-foreach i = {1-7,9-15,18,20-28} in
+foreach i = {1-7,9-15,18,20-28,30} in
     def FeatureReserveX#i : SubtargetFeature<"reserve-x"#i, "ReserveXRegister["#i#"]", "true",
                                              "Reserve X"#i#", making it unavailable "
                                              "as a GPR">;

llvm/test/CodeGen/AArch64/arm64-platform-reg.ll

@@ -29,6 +29,7 @@
 ; RUN: llc -mtriple=arm64-linux-gnu -mattr=+reserve-x26 -o - %s | FileCheck %s --check-prefixes=CHECK-RESERVE,CHECK-RESERVE-X26
 ; RUN: llc -mtriple=arm64-linux-gnu -mattr=+reserve-x27 -o - %s | FileCheck %s --check-prefixes=CHECK-RESERVE,CHECK-RESERVE-X27
 ; RUN: llc -mtriple=arm64-linux-gnu -mattr=+reserve-x28 -o - %s | FileCheck %s --check-prefixes=CHECK-RESERVE,CHECK-RESERVE-X28
+; RUN: llc -mtriple=arm64-linux-gnu -mattr=+reserve-x30 -o - %s | FileCheck %s --check-prefixes=CHECK-RESERVE,CHECK-RESERVE-X30
 
 ; Test multiple of reserve-x# options together.
 ; RUN: llc -mtriple=arm64-linux-gnu \
@@ -67,6 +68,7 @@
 ; RUN: -mattr=+reserve-x26 \
 ; RUN: -mattr=+reserve-x27 \
 ; RUN: -mattr=+reserve-x28 \
+; RUN: -mattr=+reserve-x30 \
 ; RUN: -o - %s | FileCheck %s \
 ; RUN: --check-prefix=CHECK-RESERVE \
 ; RUN: --check-prefix=CHECK-RESERVE-X1 \
@@ -92,7 +94,8 @@
 ; RUN: --check-prefix=CHECK-RESERVE-X25 \
 ; RUN: --check-prefix=CHECK-RESERVE-X26 \
 ; RUN: --check-prefix=CHECK-RESERVE-X27 \
-; RUN: --check-prefix=CHECK-RESERVE-X28
+; RUN: --check-prefix=CHECK-RESERVE-X28 \
+; RUN: --check-prefix=CHECK-RESERVE-X30
 
 ; x18 is reserved as a platform register on Darwin but not on other
 ; systems. Create loads of register pressure and make sure this is respected.
@@ -134,6 +137,7 @@ define void @keep_live() {
 ; CHECK-RESERVE-X26-NOT: ldr x26
 ; CHECK-RESERVE-X27-NOT: ldr x27
 ; CHECK-RESERVE-X28-NOT: ldr x28
+; CHECK-RESERVE-X30-NOT: ldr x30
 ; CHECK-RESERVE: Spill
 ; CHECK-RESERVE-NOT: ldr fp
 ; CHECK-RESERVE-X1-NOT: ldr x1,
@@ -160,6 +164,7 @@ define void @keep_live() {
 ; CHECK-RESERVE-X26-NOT: ldr x26
 ; CHECK-RESERVE-X27-NOT: ldr x27
 ; CHECK-RESERVE-X28-NOT: ldr x28
+; CHECK-RESERVE-X30-NOT: ldr x30
 ; CHECK-RESERVE: ret
   ret void
 }