[llvm] [polly] Slightly improve the getenv("bar") linking problem (PR #150020)

[Luke Drummond via llvm-commits]

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@@ -48,20 +48,26 @@
 #include <cstdlib>
 
 namespace llvm {
+inline bool getNonFoldableAlwaysTrue() {
+  // Some parts of the codebase require a "constant true value" used as a
+  // predicate. These cases require that even with LTO and static linking,
+  // it's not possible to for the compiler to fold the value. As compilers
+  // aren't smart enough to know that getenv() never returns -1, this will do
+  // the job.
+  return std::getenv("LLVM_IGNORED_ENV_VAR") != (char *)-1;
+}
 class Triple;
 }
 
 namespace {
 struct ForcePassLinking {
   ForcePassLinking() {
-    // We must reference the passes in such a way that compilers will not
-    // delete it all as dead code, even with whole program optimization,
-    // yet is effectively a NO-OP. As the compiler isn't smart enough
-    // to know that getenv() never returns -1, this will do the job.
-    // This is so that globals in the translation units where these functions
-    // are defined are forced to be initialized, populating various
-    // registries.
-    if (std::getenv("bar") != (char *)-1)
+    // We must reference the passes in such a way that compilers will not delete
+    // it all as dead code, even with whole program optimization, yet is
+    // effectively a NO-OP. // This is so that globals in the translation units
----------------
ldrumm wrote:

Done

https://github.com/llvm/llvm-project/pull/150020