[llvm] TableGen: Use StringOffsetTable for RuntimeLibcall names (PR #148839)

[Slava Zakharin via llvm-commits]

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@@ -116,19 +116,40 @@ def BlahLibrary : SystemRuntimeLibrary<isBlahArch, (add calloc, LibraryWithCondi
 // CHECK-NEXT:   RTLIB::Unsupported
 // CHECK-NEXT: };
 // CHECK-EMPTY:
-// CHECK-NEXT: const char *const llvm::RTLIB::RuntimeLibcallsInfo::LibCallImplNames[RTLIB::NumLibcallImpls] = {
-// CHECK-NEXT: nullptr, // RTLIB::Unsupported
-// CHECK-NEXT: "___memcpy", // RTLIB::___memcpy
-// CHECK-NEXT: "___memset", // RTLIB::___memset
-// CHECK-NEXT: "__ashlsi3", // RTLIB::__ashlsi3
-// CHECK-NEXT: "__lshrdi3", // RTLIB::__lshrdi3
-// CHECK-NEXT: "bzero", // RTLIB::bzero
-// CHECK-NEXT: "calloc", // RTLIB::calloc
-// CHECK-NEXT: "sqrtl", // RTLIB::sqrtl_f80
-// CHECK-NEXT: "sqrtl", // RTLIB::sqrtl_f128
+// CHECK-EMPTY:
+// CHECK-NEXT: #ifdef __GNUC__
+// CHECK-NEXT: #pragma GCC diagnostic push
+// CHECK-NEXT: #pragma GCC diagnostic ignored "-Woverlength-strings"
+// CHECK-NEXT: #endif
+// CHECK-NEXT:  constexpr char RTLIB::RuntimeLibcallsInfo::RuntimeLibcallImplNameTableStorage[] =
+// CHECK-NEXT:   "\0"
+// CHECK-NEXT:   "___memcpy\0"
+// CHECK-NEXT:   "___memset\0"
+// CHECK-NEXT:   "__ashlsi3\0"
+// CHECK-NEXT:   "__lshrdi3\0"
+// CHECK-NEXT:   "bzero\0"
+// CHECK-NEXT:   "calloc\0"
+// CHECK-NEXT:   "sqrtl\0"
+// CHECK-NEXT:   ;
+// CHECK-NEXT: #ifdef __GNUC__
+// CHECK-NEXT: #pragma GCC diagnostic pop
+// CHECK-NEXT: #endif
+// CHECK-EMPTY:
+// CHECK-NEXT: constexpr llvm::StringTable
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vzakhari wrote:

I think this may need to be `extern`, because the `constexpr` variable has internal linkage by default.  When built using gcc the `libLLVMCore.a` does not export the symbol.

https://github.com/llvm/llvm-project/pull/148839