Fixed spill stack objects are mutable

Differential Revision: https://reviews.llvm.org/D24039


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@280244 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/CodeGen/MachineFrameInfo.h

@@ -544,7 +544,8 @@ public:
 
   /// Create a spill slot at a fixed location on the stack.
   /// Returns an index with a negative value.
-  int CreateFixedSpillStackObject(uint64_t Size, int64_t SPOffset);
+  int CreateFixedSpillStackObject(uint64_t Size, int64_t SPOffset,
+                                  bool Immutable = false);
 
   /// Returns true if the specified index corresponds to a fixed stack object.
   bool isFixedObjectIndex(int ObjectIdx) const {

lib/CodeGen/MachineFunction.cpp

@@ -642,11 +642,11 @@ int MachineFrameInfo::CreateFixedObject(uint64_t Size, int64_t SPOffset,
 /// Create a spill slot at a fixed location on the stack.
 /// Returns an index with a negative value.
 int MachineFrameInfo::CreateFixedSpillStackObject(uint64_t Size,
-                                                  int64_t SPOffset) {
+                                                  int64_t SPOffset,
+                                                  bool Immutable) {
   unsigned Align = MinAlign(SPOffset, ForcedRealign ? 1 : StackAlignment);
   Align = clampStackAlignment(!StackRealignable, Align, StackAlignment);
-  Objects.insert(Objects.begin(), StackObject(Size, Align, SPOffset,
-                                              /*Immutable*/ true,
+  Objects.insert(Objects.begin(), StackObject(Size, Align, SPOffset, Immutable,
                                               /*isSS*/ true,
                                               /*Alloca*/ nullptr,
                                               /*isAliased*/ false));

test/CodeGen/Hexagon/fixed-spill-mutable.ll

@@ -0,0 +1,69 @@
+; RUN: llc -march=hexagon < %s | FileCheck %s
+
+; The early return is predicated, and the save-restore code is mixed together:
+; {
+;   p0 = cmp.eq(r0, #0)
+;   if (p0.new) r17:16 = memd(r29 + #0)
+;   memd(r29+#0) = r17:16
+; }
+; {
+;   if (p0) dealloc_return
+; }
+; The problem is that the load will execute before the store, clobbering the
+; pair r17:16.
+;
+; Check that the store and the load are not in the same packet.
+; CHECK: memd{{.*}} = r17:16
+; CHECK: }
+; CHECK: r17:16 = memd
+; CHECK-LABEL: LBB0_1:
+
+target triple = "hexagon"
+
+%struct.0 = type { i8*, %struct.1*, %struct.2*, %struct.0*, %struct.0* }
+%struct.1 = type { [60 x i8], i32, %struct.1* }
+%struct.2 = type { i8, i8, i8, i8, %union.anon }
+%union.anon = type { %struct.3* }
+%struct.3 = type { %struct.3*, %struct.2* }
+
+@var = external hidden unnamed_addr global %struct.0*, align 4
+
+declare void @bar(i8*, i32) local_unnamed_addr #0
+
+define void @foo() local_unnamed_addr #1 {
+entry:
+  %.pr = load %struct.0*, %struct.0** @var, align 4, !tbaa !1
+  %cmp2 = icmp eq %struct.0* %.pr, null
+  br i1 %cmp2, label %while.end, label %while.body.preheader
+
+while.body.preheader:                             ; preds = %entry
+  br label %while.body
+
+while.body:                                       ; preds = %while.body.preheader, %while.body
+  %0 = phi %struct.0* [ %4, %while.body ], [ %.pr, %while.body.preheader ]
+  %right = getelementptr inbounds %struct.0, %struct.0* %0, i32 0, i32 4
+  %1 = bitcast %struct.0** %right to i32*
+  %2 = load i32, i32* %1, align 4, !tbaa !5
+  %3 = bitcast %struct.0* %0 to i8*
+  tail call void @bar(i8* %3, i32 20) #1
+  store i32 %2, i32* bitcast (%struct.0** @var to i32*), align 4, !tbaa !1
+  %4 = inttoptr i32 %2 to %struct.0*
+  %cmp = icmp eq i32 %2, 0
+  br i1 %cmp, label %while.end.loopexit, label %while.body
+
+while.end.loopexit:                               ; preds = %while.body
+  br label %while.end
+
+while.end:                                        ; preds = %while.end.loopexit, %entry
+  ret void
+}
+
+attributes #0 = { optsize }
+attributes #1 = { nounwind optsize }
+
+!1 = !{!2, !2, i64 0}
+!2 = !{!"any pointer", !3, i64 0}
+!3 = !{!"omnipotent char", !4, i64 0}
+!4 = !{!"Simple C/C++ TBAA"}
+!5 = !{!6, !2, i64 16}
+!6 = !{!"0", !2, i64 0, !2, i64 4, !2, i64 8, !2, i64 12, !2, i64 16}