From 5a15d4162d1736442f9abbb61f0afd923de9ab41 Mon Sep 17 00:00:00 2001
From: Ayke van Laethem <aykevanlaethem@gmail.com>
Date: Sat, 22 Dec 2018 17:09:41 +0100
Subject: [PATCH] compiler: add optsize function attr to reduce binary size

This is also added by Clang at -Oz and results in slightly smaller
binaries.
---
 compiler/optimizer.go | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/compiler/optimizer.go b/compiler/optimizer.go
index 08d759b1..cf4b9580 100644
--- a/compiler/optimizer.go
+++ b/compiler/optimizer.go
@@ -51,6 +51,16 @@ func (c *Compiler) Optimize(optLevel, sizeLevel int, inlinerThreshold uint) erro
 		return errors.New("optimizations caused a verification failure")
 	}
 
+	if sizeLevel >= 2 {
+		// Set the "optsize" attribute to make slightly smaller binaries at the
+		// cost of some performance.
+		kind := llvm.AttributeKindID("optsize")
+		attr := c.ctx.CreateEnumAttribute(kind, 0)
+		for fn := c.mod.FirstFunction(); !fn.IsNil(); fn = llvm.NextFunction(fn) {
+			fn.AddFunctionAttr(attr)
+		}
+	}
+
 	// Run module passes.
 	modPasses := llvm.NewPassManager()
 	defer modPasses.Dispose()