[llvm] [FuncSpec] Relax restrictions on code size growth (PR #196570)

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<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-function-specialization

Author: Momchil Velikov (momchil-velikov)

<details>
<summary>Changes</summary>

This patch is a preparation for a follow-up patch which disables loop unroll in LTO pre-link pipeline, which affects code size and thus causes more functions to be rejected by the current code size growth restriction in function specialization.

---
Full diff: https://github.com/llvm/llvm-project/pull/196570.diff


2 Files Affected:

- (modified) llvm/lib/Transforms/IPO/FunctionSpecialization.cpp (+3-3) 
- (modified) llvm/test/Transforms/FunctionSpecialization/recursive-penalty.ll (+1-1) 


``````````diff
diff --git a/llvm/lib/Transforms/IPO/FunctionSpecialization.cpp b/llvm/lib/Transforms/IPO/FunctionSpecialization.cpp
index 1367940ad8ef8..c3963e28a09c4 100644
--- a/llvm/lib/Transforms/IPO/FunctionSpecialization.cpp
+++ b/llvm/lib/Transforms/IPO/FunctionSpecialization.cpp
@@ -63,9 +63,9 @@ static cl::opt<unsigned> MinFunctionSize(
     cl::desc("Don't specialize functions that have less than this number of "
              "instructions"));
 
-static cl::opt<unsigned> MaxCodeSizeGrowth(
-    "funcspec-max-codesize-growth", cl::init(3), cl::Hidden, cl::desc(
-    "Maximum codesize growth allowed per function"));
+static cl::opt<unsigned>
+    MaxCodeSizeGrowth("funcspec-max-codesize-growth", cl::init(4), cl::Hidden,
+                      cl::desc("Maximum codesize growth allowed per function"));
 
 static cl::opt<unsigned> MinCodeSizeSavings(
     "funcspec-min-codesize-savings", cl::init(20), cl::Hidden,
diff --git a/llvm/test/Transforms/FunctionSpecialization/recursive-penalty.ll b/llvm/test/Transforms/FunctionSpecialization/recursive-penalty.ll
index fc17387dec94d..03eb8df046e5d 100644
--- a/llvm/test/Transforms/FunctionSpecialization/recursive-penalty.ll
+++ b/llvm/test/Transforms/FunctionSpecialization/recursive-penalty.ll
@@ -6,7 +6,7 @@
 ; Make sure the number of specializations created are not
 ; linear to the number of iterations (funcspec-max-iters).
 
-; CHECK: FnSpecialization: Created 4 specializations in module
+; CHECK: FnSpecialization: Created 6 specializations in module
 
 @Global = internal constant i32 1, align 4
 

``````````

</details>


https://github.com/llvm/llvm-project/pull/196570