[Frontend] Print least valid pointer value in -print-target-info

This allows swift-driver to use the value when constructing the
linker command line for platforms that need it like WebAssembly.

Author: kateinoigakukun

include/swift/Basic/Platform.h

@@ -25,6 +25,7 @@ namespace llvm {
 }
 
 namespace swift {
+  class LangOptions;
 
   enum class DarwinPlatformKind : unsigned {
     MacOS,
@@ -75,6 +76,12 @@ namespace swift {
   /// that enforces BTCFI by default.
   bool tripleBTCFIByDefaultInOpenBSD(const llvm::Triple &triple);
 
+  /// Returns the least valid pointer value for the given target triple.
+  uint64_t
+  getLeastValidPointerValueForTriple(const llvm::Triple &triple,
+                                     const LangOptions &LangOpts,
+                                     uint64_t customLeastValidPointerValue);
+
   /// Returns the platform name for a given target triple.
   ///
   /// For example, the iOS simulator has the name "iphonesimulator", while real

lib/Basic/Platform.cpp

@@ -11,6 +11,9 @@
 //===----------------------------------------------------------------------===//
 
 #include "swift/Basic/Assertions.h"
+#include "swift/ABI/System.h"
+#include "swift/Basic/Feature.h"
+#include "swift/Basic/LangOptions.h"
 #include "swift/Basic/Pack.h"
 #include "swift/Basic/Platform.h"
 #include "llvm/ADT/StringExtras.h"
@@ -144,6 +147,33 @@ bool swift::tripleBTCFIByDefaultInOpenBSD(const llvm::Triple &triple) {
   return triple.isOSOpenBSD() && triple.getArch() == llvm::Triple::aarch64;
 }
 
+uint64_t swift::getLeastValidPointerValueForTriple(const llvm::Triple &triple,
+                                                  const LangOptions &LangOpts,
+                                                  uint64_t customLeastValidPointerValue) {
+  if (customLeastValidPointerValue != 0)
+    return customLeastValidPointerValue;
+
+  uint64_t value = SWIFT_ABI_DEFAULT_LEAST_VALID_POINTER;
+
+  if (triple.isOSDarwin() && !LangOpts.hasFeature(Feature::Embedded)) {
+    // Non-embedded Darwin reserves the low 4GB of address space.
+    switch (triple.getArch()) {
+    case llvm::Triple::x86_64:
+      value = SWIFT_ABI_DARWIN_X86_64_LEAST_VALID_POINTER;
+      break;
+    case llvm::Triple::aarch64:
+      value = SWIFT_ABI_DARWIN_ARM64_LEAST_VALID_POINTER;
+      break;
+    default:
+      break;
+    }
+  } else if (triple.getArch() == llvm::Triple::wasm32) {
+    value = SWIFT_ABI_WASM32_LEAST_VALID_POINTER;
+  }
+
+  return value;
+}
+
 DarwinPlatformKind swift::getDarwinPlatformKind(const llvm::Triple &triple) {
   if (triple.isiOS()) {
     if (triple.isTvOS()) {

lib/Basic/TargetInfo.cpp

@@ -157,6 +157,11 @@ void printTripleInfo(const CompilerInvocation &invocation,
   out << "    \"pointerWidthInBytes\": "
       << TI->getPointerWidth(clang::LangAS::Default) / TI->getCharWidth()
       << ",\n";
+  out << "    \"leastValidPointerValue\": "
+      << getLeastValidPointerValueForTriple(
+             triple, invocation.getLangOptions(),
+             invocation.getIRGenOptions().CustomLeastValidPointerValue)
+      << ",\n";
 
   if (runtimeVersion) {
     out << "    \"swiftRuntimeCompatibilityVersion\": \"";

lib/IRGen/SwiftTargetInfo.cpp

@@ -49,14 +49,6 @@ static void configureARM64(IRGenModule &IGM, const llvm::Triple &triple,
   }
   setToMask(target.IsObjCPointerBit, 64, SWIFT_ABI_ARM64_IS_OBJC_BIT);
 
-  // Non-embedded Darwin reserves the low 4GB of address space.
-  if (triple.isOSDarwin() &&
-      !IGM.getSwiftModule()->getASTContext().LangOpts.hasFeature(
-          Feature::Embedded)) {
-    target.LeastValidPointerValue =
-      SWIFT_ABI_DARWIN_ARM64_LEAST_VALID_POINTER;
-  }
-
   // arm64 has no special objc_msgSend variants, not even stret.
   target.ObjCUseStret = false;
 
@@ -107,13 +99,6 @@ static void configureX86_64(IRGenModule &IGM, const llvm::Triple &triple,
               SWIFT_ABI_X86_64_OBJC_RESERVED_BITS_MASK);
   }
 
-  if (triple.isOSDarwin() &&
-      !IGM.getSwiftModule()->getASTContext().LangOpts.hasFeature(
-          Feature::Embedded)) {
-    target.LeastValidPointerValue =
-      SWIFT_ABI_DARWIN_X86_64_LEAST_VALID_POINTER;
-  }
-
   // x86-64 has every objc_msgSend variant known to humankind.
   target.ObjCUseFPRet = true;
   target.ObjCUseFP2Ret = true;
@@ -184,8 +169,6 @@ static void configureSystemZ(IRGenModule &IGM, const llvm::Triple &triple,
 /// Configures target-specific information for wasm32 platforms.
 static void configureWasm32(IRGenModule &IGM, const llvm::Triple &triple,
                             SwiftTargetInfo &target) {
-  target.LeastValidPointerValue =
-    SWIFT_ABI_WASM32_LEAST_VALID_POINTER;
 }
 
 /// Configure a default target.
@@ -268,8 +251,9 @@ SwiftTargetInfo SwiftTargetInfo::get(IRGenModule &IGM) {
     break;
   }
 
-  if (IGM.getOptions().CustomLeastValidPointerValue != 0)
-    target.LeastValidPointerValue = IGM.getOptions().CustomLeastValidPointerValue;
+  target.LeastValidPointerValue = getLeastValidPointerValueForTriple(
+      triple, IGM.Context.LangOpts,
+      IGM.getOptions().CustomLeastValidPointerValue);
 
   return target;
 }