Edit Semantics Description of @llvm.is.constant.*

[NCGThompson]

Fixes #77517

I edited it from browser and didn't run any checks due to the triviality of the change.

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[llvmbot]

@llvm/pr-subscribers-llvm-ir

Author: Nic (NCGThompson)

Changes

Fixes #77517

I edited it from browser and didn't run any checks due to the triviality of the change.

---

Full diff: https://github.com/llvm/llvm-project/pull/77519.diff

1 Files Affected:

• (modified) llvm/docs/LangRef.rst (-3)

diff --git a/llvm/docs/LangRef.rst b/llvm/docs/LangRef.rst
index c90b6becae5254..a16899205b22e5 100644
--- a/llvm/docs/LangRef.rst
+++ b/llvm/docs/LangRef.rst
@@ -27220,9 +27220,6 @@ obviously not constant. However, a call like
 function is inlined, if the value passed to the function parameter was
 a constant.
 
-On the other hand, if constant folding is not run, it will never
-evaluate to true, even in simple cases.
-
 .. _int_ptrmask:
 
 '``llvm.ptrmask``' Intrinsic

[jyknight]

I think this may have been true at one point, but hasn't been for some time.

[jsonn]

The Lower-Constant-Intrinsic pass will remove all instructions that haven't been folded otherwise. It folds to true for material constants and false otherwise. As such, the statement is false for all normal optimization pipelines.

[NCGThompson]

The Lower-Constant-Intrinsic pass will remove all instructions that haven't been folded otherwise. It folds to true for material constants and false otherwise. As such, the statement is false for all normal optimization pipelines.

There is an exception with alwaysinline if @llvm.is.constant is called directly on a function's input. @llvm.is.constant while be optimized to true, but the true won't be propagated further with -O0.