[llvm] [docs] mention that DenseMap has a SmallDenseMap variant (PR #70677)

[Nick Desaulniers via llvm-commits]

https://github.com/nickdesaulniers created https://github.com/llvm/llvm-project/pull/70677

via https://github.com/llvm/llvm-project/pull/67699/files#r1375105711


>From eba0797c332205d4e1e2b443a1054ca4e3e423ea Mon Sep 17 00:00:00 2001
From: Nick Desaulniers <ndesaulniers at google.com>
Date: Mon, 30 Oct 2023 09:05:20 -0700
Subject: [PATCH] [docs] mention that DenseMap has a SmallDenseMap variant

via https://github.com/llvm/llvm-project/pull/67699/files#r1375105711
---
 llvm/docs/ProgrammersManual.rst | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/llvm/docs/ProgrammersManual.rst b/llvm/docs/ProgrammersManual.rst
index 22e95261e639256..5bc71bea77cdfc6 100644
--- a/llvm/docs/ProgrammersManual.rst
+++ b/llvm/docs/ProgrammersManual.rst
@@ -2323,6 +2323,10 @@ construct, but cheap to compare against.  The DenseMapInfo is responsible for
 defining the appropriate comparison and hashing methods for each alternate key
 type used.
 
+DenseMap.h also contains a SmallDenseMap variant, that similar to
+:ref:`SmallVector <dss_smallvector>` performs no heap allocation until the
+number of elements in the template parameter N are exceeded.
+
 .. _dss_valuemap:
 
 llvm/IR/ValueMap.h