[Flang][Driver] Predefine pic/pie macros based on configured level (#153449)

Predefine the `__pic__/__pie__/__PIC__/__PIE__` macros based on the
configured relocation level. This logic mirrors that of the clang
driver, where `__pic__/__PIC__` are defined for both PIC and PIE modes,
but `__pie__/__PIE__` are only defined for PIE mode.

Fixes #135275

Author: imciner2

flang/lib/Frontend/CompilerInvocation.cpp

@@ -1703,6 +1703,20 @@ void CompilerInvocation::setDefaultPredefinitions() {
   fortranOptions.predefinitions.emplace_back("__flang_patchlevel__",
                                              FLANG_VERSION_PATCHLEVEL_STRING);
 
+  // Add predefinitions based on the relocation model
+  if (unsigned PICLevel = getCodeGenOpts().PICLevel) {
+    fortranOptions.predefinitions.emplace_back("__PIC__",
+                                               std::to_string(PICLevel));
+    fortranOptions.predefinitions.emplace_back("__pic__",
+                                               std::to_string(PICLevel));
+    if (getCodeGenOpts().IsPIE) {
+      fortranOptions.predefinitions.emplace_back("__PIE__",
+                                                 std::to_string(PICLevel));
+      fortranOptions.predefinitions.emplace_back("__pie__",
+                                                 std::to_string(PICLevel));
+    }
+  }
+
   // Add predefinitions based on extensions enabled
   if (frontendOptions.features.IsEnabled(
           Fortran::common::LanguageFeature::OpenACC)) {

flang/test/Preprocessing/defines_pic_frontend.F90

@@ -0,0 +1,38 @@
+! Check that the pie/pic/PIE/PIC macros are defined properly through the frontend driver
+
+! RUN: %flang_fc1 -dM -E -o - %s \
+! RUN:   | FileCheck %s
+! CHECK-NOT: #define __PIC__
+! CHECK-NOT: #define __PIE__
+! CHECK-NOT: #define __pic__
+! CHECK-NOT: #define __pie__
+!
+! RUN: %flang_fc1 -pic-level 1 -dM -E -o - %s \
+! RUN:   | FileCheck --check-prefix=CHECK-PIC1 %s
+! CHECK-PIC1: #define __PIC__ 1
+! CHECK-PIC1-NOT: #define __PIE__
+! CHECK-PIC1: #define __pic__ 1
+! CHECK-PIC1-NOT: #define __pie__
+!
+! RUN: %flang_fc1 -pic-level 2 -dM -E -o - %s \
+! RUN:   | FileCheck --check-prefix=CHECK-PIC2 %s
+! CHECK-PIC2: #define __PIC__ 2
+! CHECK-PIC2-NOT: #define __PIE__
+! CHECK-PIC2: #define __pic__ 2
+! CHECK-PIC2-NOT: #define __pie__
+!
+! RUN: %flang_fc1 -pic-level 1 -pic-is-pie -dM -E -o - %s \
+! RUN:   | FileCheck --check-prefix=CHECK-PIE1 %s
+! CHECK-PIE1: #define __PIC__ 1
+! CHECK-PIE1: #define __PIE__ 1
+! CHECK-PIE1: #define __pic__ 1
+! CHECK-PIE1: #define __pie__ 1
+!
+! RUN: %flang_fc1 -pic-level 2 -pic-is-pie -dM -E -o - %s \
+! RUN:   | FileCheck --check-prefix=CHECK-PIE2 %s
+! CHECK-PIE2: #define __PIC__ 2
+! CHECK-PIE2: #define __PIE__ 2
+! CHECK-PIE2: #define __pic__ 2
+! CHECK-PIE2: #define __pie__ 2
+
+integer, parameter :: pic_level = __pic__