From c5cb2cec9b7c8e4cee016d4c5c485e83dc872d05 Mon Sep 17 00:00:00 2001
From: Ayke van Laethem <aykevanlaethem@gmail.com>
Date: Wed, 18 Mar 2020 20:41:19 +0100
Subject: [PATCH] compiler: move NonConstGlobals pass to transform package

---
 builder/build.go                            |  2 +-
 compiler/compiler.go                        | 11 -----------
 transform/globals.go                        | 13 +++++++++++++
 transform/globals_test.go                   |  7 +++++++
 transform/testdata/globals-non-const.ll     |  5 +++++
 transform/testdata/globals-non-const.out.ll |  5 +++++
 6 files changed, 31 insertions(+), 12 deletions(-)
 create mode 100644 transform/testdata/globals-non-const.ll
 create mode 100644 transform/testdata/globals-non-const.out.ll

diff --git a/builder/build.go b/builder/build.go
index c1d82370..e7029afd 100644
--- a/builder/build.go
+++ b/builder/build.go
@@ -98,7 +98,7 @@ func Build(pkgName, outpath string, config *compileopts.Config, action func(stri
 	// pointers are flash and which are in RAM so that pointers can have a
 	// correct address space parameter (address space 1 is for flash).
 	if strings.HasPrefix(config.Triple(), "avr") {
-		c.NonConstGlobals()
+		transform.NonConstGlobals(c.Module())
 		if err := c.Verify(); err != nil {
 			return errors.New("verification error after making all globals non-constant on AVR")
 		}
diff --git a/compiler/compiler.go b/compiler/compiler.go
index 8556f839..609d57f7 100644
--- a/compiler/compiler.go
+++ b/compiler/compiler.go
@@ -2585,17 +2585,6 @@ func (c *Compiler) Verify() error {
 	return llvm.VerifyModule(c.mod, llvm.PrintMessageAction)
 }
 
-// Turn all global constants into global variables. This works around a
-// limitation on Harvard architectures (e.g. AVR), where constant and
-// non-constant pointers point to a different address space.
-func (c *Compiler) NonConstGlobals() {
-	global := c.mod.FirstGlobal()
-	for !global.IsNil() {
-		global.SetGlobalConstant(false)
-		global = llvm.NextGlobal(global)
-	}
-}
-
 // Emit object file (.o).
 func (c *Compiler) EmitObject(path string) error {
 	llvmBuf, err := c.machine.EmitToMemoryBuffer(c.mod, llvm.ObjectFile)
diff --git a/transform/globals.go b/transform/globals.go
index c142fed8..89386fd8 100644
--- a/transform/globals.go
+++ b/transform/globals.go
@@ -18,3 +18,16 @@ func ApplyFunctionSections(mod llvm.Module) {
 		llvmFn = llvm.NextFunction(llvmFn)
 	}
 }
+
+// NonConstGlobals turns all global constants into global variables. This works
+// around a limitation on Harvard architectures (e.g. AVR), where constant and
+// non-constant pointers point to a different address space. Normal pointer
+// behavior is restored by using the data space only, at the cost of RAM for
+// constant global variables.
+func NonConstGlobals(mod llvm.Module) {
+	global := mod.FirstGlobal()
+	for !global.IsNil() {
+		global.SetGlobalConstant(false)
+		global = llvm.NextGlobal(global)
+	}
+}
diff --git a/transform/globals_test.go b/transform/globals_test.go
index 0dcb0608..14c77e6a 100644
--- a/transform/globals_test.go
+++ b/transform/globals_test.go
@@ -12,3 +12,10 @@ func TestApplyFunctionSections(t *testing.T) {
 		ApplyFunctionSections(mod)
 	})
 }
+
+func TestNonConstGlobals(t *testing.T) {
+	t.Parallel()
+	testTransform(t, "testdata/globals-non-const", func(mod llvm.Module) {
+		NonConstGlobals(mod)
+	})
+}
diff --git a/transform/testdata/globals-non-const.ll b/transform/testdata/globals-non-const.ll
new file mode 100644
index 00000000..5f3c5846
--- /dev/null
+++ b/transform/testdata/globals-non-const.ll
@@ -0,0 +1,5 @@
+target datalayout = "e-m:e-p:32:32-Fi8-i64:64-v128:64:128-a:0:32-n32-S64"
+target triple = "armv7em-none-eabi"
+
+@globalIntConst = constant i32 3
+@globalIntVar = global i32 5
diff --git a/transform/testdata/globals-non-const.out.ll b/transform/testdata/globals-non-const.out.ll
new file mode 100644
index 00000000..33b577eb
--- /dev/null
+++ b/transform/testdata/globals-non-const.out.ll
@@ -0,0 +1,5 @@
+target datalayout = "e-m:e-p:32:32-Fi8-i64:64-v128:64:128-a:0:32-n32-S64"
+target triple = "armv7em-none-eabi"
+
+@globalIntConst = global i32 3
+@globalIntVar = global i32 5