[libc] [lldb] [mlir] [clang-tools-extra] [flang] [clang] [llvm] [compiler-rt] [libcxx] [X86] Add "Ws" constraint and "p" modifier for symbolic address/label reference (PR #77886)

[Fangrui Song via cfe-commits]

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@@ -1418,6 +1418,14 @@ bool X86TargetInfo::validateAsmConstraint(
   case 'O':
     Info.setRequiresImmediate(0, 127);
     return true;
+  case 'W':
+    switch (*++Name) {
+    default:
+      return false;
+    case 's':
+      Info.setAllowsRegister();
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MaskRay wrote:

`setAllowsRegister` is somewhat confusing but its use is correct here (also used by aarch64/riscv `S`).

`setAllowsMemory` seems to not add extra checks.

https://github.com/llvm/llvm-project/pull/77886