[LLVM][IR] Replace unsigned >= ConstantDataFirstVal with static_assert

[jurahul]

ConstantDataFirstVal is 0, so getValueID() >= ConstantDataFirstVal leads to a compiler warning that the expression is always true. Replace such comparisons with a static_assert() to verify that ConstantDataFirstVal is 0, similar to the existing code in Value.h

[jurahul]

Seems to be triggered by 1ead4a8

[llvmbot]

@llvm/pr-subscribers-llvm-ir

Author: Rahul Joshi (jurahul)

Changes

ConstantDataFirstVal is 0, so getValueID() >= ConstantDataFirstVal leads to a compiler warning that the expression is always true. Replace such comparisons with a static_assert() to verify that ConstantDataFirstVal is 0, similar to the existing code in Value.h

---

Full diff: https://github.com/llvm/llvm-project/pull/140827.diff

2 Files Affected:

• (modified) llvm/include/llvm/IR/Constants.h (+3-2)
• (modified) llvm/include/llvm/IR/Value.h (+5-3)

diff --git a/llvm/include/llvm/IR/Constants.h b/llvm/include/llvm/IR/Constants.h
index 7137c699cc992..6a01e8209071d 100644
--- a/llvm/include/llvm/IR/Constants.h
+++ b/llvm/include/llvm/IR/Constants.h
@@ -74,8 +74,9 @@ class ConstantData : public Constant {
 
   /// Methods to support type inquiry through isa, cast, and dyn_cast.
   static bool classof(const Value *V) {
-    return V->getValueID() >= ConstantDataFirstVal &&
-           V->getValueID() <= ConstantDataLastVal;
+    static_assert(Value::ConstantDataFirstVal == 0,
+                  "V->getValueID() >= Value::ConstantDataFirstVal");
+    return V->getValueID() <= ConstantDataLastVal;
   }
 };
 
diff --git a/llvm/include/llvm/IR/Value.h b/llvm/include/llvm/IR/Value.h
index c276899e673a3..999eeb3dad874 100644
--- a/llvm/include/llvm/IR/Value.h
+++ b/llvm/include/llvm/IR/Value.h
@@ -987,15 +987,17 @@ template <class Compare> void Value::sortUseList(Compare Cmp) {
 //
 template <> struct isa_impl<Constant, Value> {
   static inline bool doit(const Value &Val) {
-    static_assert(Value::ConstantFirstVal == 0, "Val.getValueID() >= Value::ConstantFirstVal");
+    static_assert(Value::ConstantFirstVal == 0,
+                  "Val.getValueID() >= Value::ConstantFirstVal");
     return Val.getValueID() <= Value::ConstantLastVal;
   }
 };
 
 template <> struct isa_impl<ConstantData, Value> {
   static inline bool doit(const Value &Val) {
-    return Val.getValueID() >= Value::ConstantDataFirstVal &&
-           Val.getValueID() <= Value::ConstantDataLastVal;
+    static_assert(Value::ConstantDataFirstVal == 0,
+                  "Val.getValueID() >= Value::ConstantDataFirstVal");
+    return Val.getValueID() <= Value::ConstantDataLastVal;
   }
 };
 

[jurahul]

This caused build failures for our downstream build that had warning-as-error enabled. Particularly https://learn.microsoft.com/en-us/cpp/error-messages/compiler-warnings/compiler-warning-level-4-c4296?view=msvc-170