[M68k] Change gcc register name from a7 to sp. (llvm#87095)

In M68kRegisterInfo.td, register SP is defined with name sp and
alternate name a7.

Fixes: llvm#78620

Author: tclin914

clang/lib/Basic/Targets/M68k.cpp

@@ -127,16 +127,21 @@ bool M68kTargetInfo::hasFeature(StringRef Feature) const {
 
 const char *const M68kTargetInfo::GCCRegNames[] = {
     "d0", "d1", "d2", "d3", "d4", "d5", "d6", "d7",
-    "a0", "a1", "a2", "a3", "a4", "a5", "a6", "a7",
+    "a0", "a1", "a2", "a3", "a4", "a5", "a6", "sp",
     "pc"};
 
 ArrayRef<const char *> M68kTargetInfo::getGCCRegNames() const {
   return llvm::ArrayRef(GCCRegNames);
 }
 
+const TargetInfo::GCCRegAlias M68kTargetInfo::GCCRegAliases[] = {
+    {{"bp"}, "a5"},
+    {{"fp"}, "a6"},
+    {{"usp", "ssp", "isp", "a7"}, "sp"},
+};
+
 ArrayRef<TargetInfo::GCCRegAlias> M68kTargetInfo::getGCCRegAliases() const {
-  // No aliases.
-  return std::nullopt;
+  return llvm::ArrayRef(GCCRegAliases);
 }
 
 bool M68kTargetInfo::validateAsmConstraint(

clang/lib/Basic/Targets/M68k.h

@@ -25,6 +25,7 @@ namespace targets {
 
 class LLVM_LIBRARY_VISIBILITY M68kTargetInfo : public TargetInfo {
   static const char *const GCCRegNames[];
+  static const TargetInfo::GCCRegAlias GCCRegAliases[];
 
   enum CPUKind {
     CK_Unknown,

clang/test/CodeGen/M68k/inline-asm-gcc-regs.c

@@ -0,0 +1,134 @@
+// RUN: %clang_cc1 -triple m68k -emit-llvm -O2 %s -o - | FileCheck %s
+
+/// Check GCC register names and alias can be used in register variable definition.
+
+// CHECK-LABEL: @test_d0
+// CHECK: call void asm sideeffect "", "{d0}"(i32 undef)
+void test_d0() {
+    register int a asm ("d0");
+    asm ("" :: "r" (a));
+}
+
+// CHECK-LABEL: @test_d1
+// CHECK: call void asm sideeffect "", "{d1}"(i32 undef)
+void test_d1() {
+    register int a asm ("d1");
+    asm ("" :: "r" (a));
+}
+
+// CHECK-LABEL: @test_d2
+// CHECK: call void asm sideeffect "", "{d2}"(i32 undef)
+void test_d2() {
+    register int a asm ("d2");
+    asm ("" :: "r" (a));
+}
+
+// CHECK-LABEL: @test_d3
+// CHECK: call void asm sideeffect "", "{d3}"(i32 undef)
+void test_d3() {
+    register int a asm ("d3");
+    asm ("" :: "r" (a));
+}
+
+// CHECK-LABEL: @test_d4
+// CHECK: call void asm sideeffect "", "{d4}"(i32 undef)
+void test_d4() {
+    register int a asm ("d4");
+    asm ("" :: "r" (a));
+}
+
+// CHECK-LABEL: @test_d5
+// CHECK: call void asm sideeffect "", "{d5}"(i32 undef)
+void test_d5() {
+    register int a asm ("d5");
+    asm ("" :: "r" (a));
+}
+
+// CHECK-LABEL: @test_d6
+// CHECK: call void asm sideeffect "", "{d6}"(i32 undef)
+void test_d6() {
+    register int a asm ("d6");
+    asm ("" :: "r" (a));
+}
+
+// CHECK-LABEL: @test_d7
+// CHECK: call void asm sideeffect "", "{d7}"(i32 undef)
+void test_d7() {
+    register int a asm ("d7");
+    asm ("" :: "r" (a));
+}
+
+// CHECK-LABEL: @test_a0
+// CHECK: call void asm sideeffect "", "{a0}"(i32 undef)
+void test_a0() {
+    register int a asm ("a0");
+    asm ("" :: "r" (a));
+}
+
+// CHECK-LABEL: @test_a1
+// CHECK: call void asm sideeffect "", "{a1}"(i32 undef)
+void test_a1() {
+    register int a asm ("a1");
+    asm ("" :: "r" (a));
+}
+
+// CHECK-LABEL: @test_a2
+// CHECK: call void asm sideeffect "", "{a2}"(i32 undef)
+void test_a2() {
+    register int a asm ("a2");
+    asm ("" :: "r" (a));
+}
+
+// CHECK-LABEL: @test_a3
+// CHECK: call void asm sideeffect "", "{a3}"(i32 undef)
+void test_a3() {
+    register int a asm ("a3");
+    asm ("" :: "r" (a));
+}
+
+// CHECK-LABEL: @test_a4
+// CHECK: call void asm sideeffect "", "{a4}"(i32 undef)
+void test_a4() {
+    register int a asm ("a4");
+    asm ("" :: "r" (a));
+}
+
+// CHECK-LABEL: @test_a5
+// CHECK: call void asm sideeffect "", "{a5}"(i32 undef)
+void test_a5() {
+    register int a asm ("a5");
+    register int b asm ("bp");
+    asm ("" :: "r" (a));
+    asm ("" :: "r" (b));
+}
+
+// CHECK-LABEL: @test_a6
+// CHECK: call void asm sideeffect "", "{a6}"(i32 undef)
+void test_a6() {
+    register int a asm ("a6");
+    register int b asm ("fp");
+    asm ("" :: "r" (a));
+    asm ("" :: "r" (b));
+}
+
+// CHECK-LABEL: @test_sp
+// CHECK: call void asm sideeffect "", "{sp}"(i32 undef)
+void test_sp() {
+    register int a asm ("sp");
+    register int b asm ("usp");
+    register int c asm ("ssp");
+    register int d asm ("isp");
+    register int e asm ("a7");
+    asm ("" :: "r" (a));
+    asm ("" :: "r" (b));
+    asm ("" :: "r" (c));
+    asm ("" :: "r" (d));
+    asm ("" :: "r" (e));
+}
+
+// CHECK-LABEL: @test_pc
+// CHECK: call void asm sideeffect "", "{pc}"(i32 undef)
+void test_pc() {
+    register int a asm ("pc");
+    asm ("" :: "r" (a));
+}