[MC][LoongArch] Change default cpu in MCSubtargetInfo. (llvm#114922)

The default value of this CPU affects the `FeatureBits` obtained by
`LoongArchTargetELFStreamer` when creating an ELF file, and it will
further affect the `Flags` field in the generated file.

So, the default CPU value should be consistent with the
`initializeSubtargetDependencies` in `LoongArchSubtarget.cpp`.
Otherwise, the `Flags` field may be unexpected.

Author: ylzsx

llvm/lib/Target/LoongArch/MCTargetDesc/LoongArchMCTargetDesc.cpp

@@ -55,7 +55,7 @@ static MCInstrInfo *createLoongArchMCInstrInfo() {
 static MCSubtargetInfo *
 createLoongArchMCSubtargetInfo(const Triple &TT, StringRef CPU, StringRef FS) {
   if (CPU.empty() || CPU == "generic")
-    CPU = TT.isArch64Bit() ? "la464" : "generic-la32";
+    CPU = TT.isArch64Bit() ? "generic-la64" : "generic-la32";
   return createLoongArchMCSubtargetInfoImpl(TT, CPU, /*TuneCPU*/ CPU, FS);
 }
 

llvm/test/CodeGen/LoongArch/e_flags.ll

@@ -1,3 +1,6 @@
+; RUN: llc --mtriple=loongarch32 --filetype=obj %s -o %t-la32s
+; RUN: llvm-readelf -h %t-la32s | FileCheck %s --check-prefixes=ILP32,ABI-S --match-full-lines
+
 ; RUN: llc --mtriple=loongarch32 -mattr=+d --filetype=obj %s -o %t-la32
 ; RUN: llvm-readelf -h %t-la32 | FileCheck %s --check-prefixes=ILP32,ABI-D --match-full-lines
 
@@ -10,6 +13,9 @@
 ; RUN: llc --mtriple=loongarch32 -mattr=+d --filetype=obj %s --target-abi=ilp32d -o %t-ilp32d
 ; RUN: llvm-readelf -h %t-ilp32d | FileCheck %s --check-prefixes=ILP32,ABI-D --match-full-lines
 
+; RUN: llc --mtriple=loongarch64 --filetype=obj %s -o %t-la64d
+; RUN: llvm-readelf -h %t-la64d | FileCheck %s --check-prefixes=LP64,ABI-D --match-full-lines
+
 ; RUN: llc --mtriple=loongarch64 -mattr=+d --filetype=obj %s -o %t-la64
 ; RUN: llvm-readelf -h %t-la64 | FileCheck %s --check-prefixes=LP64,ABI-D --match-full-lines