Merge pull request #71 from TimNN/arm-backport-4.0

Backport "[ARM] Fix PR32130: Handle promotion of zero sized constants."

Author: TimNN

lib/Target/ARM/ARMISelLowering.cpp

@@ -2980,7 +2980,8 @@ static SDValue promoteToConstantPool(const GlobalValue *GV, SelectionDAG &DAG,
   unsigned RequiredPadding = 4 - (Size % 4);
   bool PaddingPossible =
     RequiredPadding == 4 || (CDAInit && CDAInit->isString());
-  if (!PaddingPossible || Align > 4 || Size > ConstpoolPromotionMaxSize)
+  if (!PaddingPossible || Align > 4 || Size > ConstpoolPromotionMaxSize ||
+      Size == 0)
     return SDValue();
 
   unsigned PaddedSize = Size + ((RequiredPadding == 4) ? 0 : RequiredPadding);

test/CodeGen/ARM/constantpool-promote.ll

@@ -16,6 +16,7 @@ target triple = "armv7--linux-gnueabihf"
 @.arr3 = private unnamed_addr constant [2 x i16*] [i16* null, i16* null], align 4
 @.ptr = private unnamed_addr constant [2 x i16*] [i16* getelementptr inbounds ([2 x i16], [2 x i16]* @.arr2, i32 0, i32 0), i16* null], align 2
 @.arr4 = private unnamed_addr constant [2 x i16] [i16 3, i16 4], align 16
+@.zerosize = private unnamed_addr constant [0 x i16] zeroinitializer, align 4
 
 ; CHECK-LABEL: @test1
 ; CHECK: adr r0, [[x:.*]]
@@ -134,6 +135,13 @@ define void @test9() #0 {
   ret void
 }
 
+; Ensure that zero sized values are supported / not promoted.
+; CHECK-LABEL: @pr32130
+; CHECK-NOT: adr
+define void @pr32130() #0 {
+  tail call void @c(i16* getelementptr inbounds ([0 x i16], [0 x i16]* @.zerosize, i32 0, i32 0)) #2
+  ret void
+}
 
 declare void @b(i8*) #1
 declare void @c(i16*) #1