[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

Author: dylanmckay

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");
   }

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)*)
+