AArch64: treat [N x Ty] as a block during procedure calls.

The AAPCS treats small structs and homogeneous floating (or vector) aggregates
specially, and guarantees they either get passed as a contiguous block of
registers, or prevent any future use of those registers and get passed on the
stack.

This concept can fit quite neatly into LLVM's own type system, mapping an HFA
to [N x float] and so on, and small structs to [N x i64]. Doing so allows
front-ends to emit AAPCS compliant code without having to duplicate the
register counting logic.

llvm-svn: 222903

1 files changed, 2 insertions, 6 deletions

diff --git a/llvm/lib/Target/ARM/ARMCallingConv.h b/llvm/lib/Target/ARM/ARMCallingConv.h
index bd07236d0ea..4567a2a1afd 100644
--- a/llvm/lib/Target/ARM/ARMCallingConv.h
+++ b/llvm/lib/Target/ARM/ARMCallingConv.h
@@ -194,20 +194,16 @@ static bool CC_ARM_AAPCS_Custom_HA(unsigned &ValNo, MVT &ValVT, MVT &LocVT,
 
     // Try to allocate a contiguous block of registers, each of the correct
     // size to hold one member.
-    const uint16_t *RegList;
-    unsigned NumRegs;
+    ArrayRef<const uint16_t> RegList;
     switch (LocVT.SimpleTy) {
     case MVT::f32:
       RegList = SRegList;
-      NumRegs = 16;
       break;
     case MVT::f64:
       RegList = DRegList;
-      NumRegs = 8;
       break;
     case MVT::v2f64:
       RegList = QRegList;
-      NumRegs = 4;
       break;
     default:
       llvm_unreachable("Unexpected member type for HA");
@@ -215,7 +211,7 @@ static bool CC_ARM_AAPCS_Custom_HA(unsigned &ValNo, MVT &ValVT, MVT &LocVT,
     }
 
     unsigned RegResult =
-        State.AllocateRegBlock(RegList, NumRegs, PendingHAMembers.size());
+        State.AllocateRegBlock(RegList, PendingHAMembers.size());
 
     if (RegResult) {
       for (SmallVectorImpl<CCValAssign>::iterator It = PendingHAMembers.begin();