From 90904c693cecb8976f9cf3a7aaf0e6be669fe794 Mon Sep 17 00:00:00 2001
From: Dylan McKay <me@dylanmckay.io>
Date: Thu, 13 Jul 2017 08:09:36 +0000
Subject: [PATCH] [AVR] Fix indirect calls to function pointers

Patch by Carl Peto.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@307888 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Target/AVR/AVRMCInstLower.cpp                | 16 ++++++++++++++--
 .../AVR/icall-func-pointer-correct-addr-space.ll | 15 +++++++++++++++
 2 files changed, 29 insertions(+), 2 deletions(-)
 create mode 100644 test/CodeGen/AVR/icall-func-pointer-correct-addr-space.ll

diff --git a/lib/Target/AVR/AVRMCInstLower.cpp b/lib/Target/AVR/AVRMCInstLower.cpp
index 475dda420e8..dfefd09bc4b 100644
--- a/lib/Target/AVR/AVRMCInstLower.cpp
+++ b/lib/Target/AVR/AVRMCInstLower.cpp
@@ -37,10 +37,22 @@ MCOperand AVRMCInstLower::lowerSymbolOperand(const MachineOperand &MO,
         Expr, MCConstantExpr::create(MO.getOffset(), Ctx), Ctx);
   }
 
+  bool IsFunction = MO.isGlobal() && isa<Function>(MO.getGlobal());
+
   if (TF & AVRII::MO_LO) {
-    Expr = AVRMCExpr::create(AVRMCExpr::VK_AVR_LO8, Expr, IsNegated, Ctx);
+    if (IsFunction) {
+      // N.B. Should we use _GS fixups here to cope with >128k progmem?
+      Expr = AVRMCExpr::create(AVRMCExpr::VK_AVR_PM_LO8, Expr, IsNegated, Ctx);
+    } else {
+      Expr = AVRMCExpr::create(AVRMCExpr::VK_AVR_LO8, Expr, IsNegated, Ctx);
+    }
   } else if (TF & AVRII::MO_HI) {
-    Expr = AVRMCExpr::create(AVRMCExpr::VK_AVR_HI8, Expr, IsNegated, Ctx);
+    if (IsFunction) {
+      // N.B. Should we use _GS fixups here to cope with >128k progmem?
+      Expr = AVRMCExpr::create(AVRMCExpr::VK_AVR_PM_HI8, Expr, IsNegated, Ctx);
+    } else {
+      Expr = AVRMCExpr::create(AVRMCExpr::VK_AVR_HI8, Expr, IsNegated, Ctx);
+    }
   } else if (TF != 0) {
     llvm_unreachable("Unknown target flag on symbol operand");
   }
diff --git a/test/CodeGen/AVR/icall-func-pointer-correct-addr-space.ll b/test/CodeGen/AVR/icall-func-pointer-correct-addr-space.ll
new file mode 100644
index 00000000000..17ac29e2cdb
--- /dev/null
+++ b/test/CodeGen/AVR/icall-func-pointer-correct-addr-space.ll
@@ -0,0 +1,15 @@
+; RUN: llc -mattr=lpm,lpmw < %s -march=avr | FileCheck %s
+
+declare void @callback(i16 zeroext)
+
+; CHECK-LABEL: foo
+define void @foo() {
+entry:
+  ; CHECK:      ldi     r{{[0-9]+}}, pm_lo8(callback)
+  ; CHECK-NEXT: ldi     r{{[0-9]+}}, pm_hi8(callback)
+  call void @bar(i8 zeroext undef, void (i16)* @callback)
+  ret void
+}
+
+declare void @bar(i8 zeroext, void (i16)*)
+