Fix return value calculation

Upon calculating NewSP we end up with a biased SP again, so we
need to account for that in NewVal return.

Author: koachan

llvm/lib/Target/Sparc/SparcISelLowering.cpp

@@ -2819,18 +2819,16 @@ static SDValue LowerDYNAMIC_STACKALLOC(SDValue Op, SelectionDAG &DAG,
     regSpillArea = 96;
   }
 
-  // If we are allocating overaligned memory then the bias is already accounted
-  // for in AlignedPtr calculation, so:
-  // - We do not need to adjust the regSpillArea; but
-  // - We do need to decrement AlignedPtr by bias to obtain the new SP.
-  regSpillArea += IsOveraligned ? 0 : Bias;
+  // If we are allocating overaligned memory then the AlignedPtr calculation
+  // adds the bias into SP, so we need to restore biased SP by decrementing
+  // AlignedPtr back here.
   SDValue NewSP =
       DAG.getNode(ISD::SUB, dl, VT, AlignedPtr,
                   DAG.getConstant(IsOveraligned ? Bias : 0, dl, VT));
   Chain = DAG.getCopyToReg(SP.getValue(1), dl, SPReg, NewSP);
 
   SDValue NewVal = DAG.getNode(ISD::ADD, dl, VT, NewSP,
-                               DAG.getConstant(regSpillArea, dl, VT));
+                               DAG.getConstant(regSpillArea + Bias, dl, VT));
   SDValue Ops[2] = { NewVal, Chain };
   return DAG.getMergeValues(Ops, dl);
 }

llvm/test/CodeGen/SPARC/alloca-align.ll

@@ -25,7 +25,7 @@ define void @variable_alloca_with_overalignment(i32 %num) nounwind {
 ; CHECK64-NEXT:    add %sp, 1967, %i1
 ; CHECK64-NEXT:    and %i1, -64, %i1
 ; CHECK64-NEXT:    add %i1, -2047, %sp
-; CHECK64-NEXT:    add %i1, -1919, %o0
+; CHECK64-NEXT:    add %i1, 128, %o0
 ; CHECK64-NEXT:    srl %i0, 0, %i0
 ; CHECK64-NEXT:    add %i0, 15, %i0
 ; CHECK64-NEXT:    sethi 4194303, %i1
@@ -82,7 +82,7 @@ define void @variable_alloca_with_overalignment_2(i32 %num) nounwind {
 ; CHECK64-NEXT:    add %i0, 1983, %i0
 ; CHECK64-NEXT:    and %i0, -64, %i0
 ; CHECK64-NEXT:    add %i0, -2047, %sp
-; CHECK64-NEXT:    add %i0, -1919, %o1
+; CHECK64-NEXT:    add %i0, 128, %o1
 ; CHECK64-NEXT:    add %sp, -48, %sp
 ; CHECK64-NEXT:    call foo
 ; CHECK64-NEXT:    mov %g0, %o0

llvm/test/CodeGen/SPARC/stack-align.ll

@@ -27,7 +27,7 @@ define void @stack_realign(i32 %a, i32 %b, i32 %c, i32 %d, i32 %e, i32 %f, i32 %
 ; CHECK64-NEXT:    add %sp, 1967, %i0
 ; CHECK64-NEXT:    and %i0, -64, %i0
 ; CHECK64-NEXT:    add %i0, -2047, %sp
-; CHECK64-NEXT:    add %i0, -1919, %o1
+; CHECK64-NEXT:    add %i0, 128, %o1
 ; CHECK64-NEXT:    add %sp, -48, %sp
 ; CHECK64-NEXT:    call stack_realign_helper
 ; CHECK64-NEXT:    ld [%fp+2227], %o0