Teach the SLP Vectorizer that keeping some values live over a callsite can have a cost.

Some types, such as 128-bit vector types on AArch64, don't have any callee-saved registers. So if a value needs to stay live over a callsite, it must be spilled and refilled. This cost is now taken into account.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214859 91177308-0d34-0410-b5e6-96231b3b80d8

test/Transforms/SLPVectorizer/AArch64/load-store-q.ll

@@ -0,0 +1,46 @@
+; RUN: opt -S -basicaa -slp-vectorizer < %s | FileCheck %s
+target datalayout = "e-m:o-i64:64-i128:128-n32:64-S128"
+target triple = "arm64-apple-ios5.0.0"
+
+; Holding a value live over a call boundary may require
+; spills and fills. This is the case for <2 x double>,
+; as it occupies a Q register of which there are no
+; callee-saves.
+ 
+; CHECK: load double
+; CHECK: load double
+; CHECK: call void @g
+; CHECK: store double
+; CHECK: store double
+define void @f(double* %p, double* %q) {
+  %addr2 = getelementptr double* %q, i32 1
+  %addr = getelementptr double* %p, i32 1
+  %x = load double* %p
+  %y = load double* %addr
+  call void @g()
+  store double %x, double* %q
+  store double %y, double* %addr2
+  ret void
+}
+declare void @g()
+
+; Check we deal with loops correctly.
+;
+; CHECK: store <2 x double>
+; CHECK: load <2 x double>
+define void @f2(double* %p, double* %q) {
+entry:
+  br label %loop
+
+loop:
+  %p1 = phi double [0.0, %entry], [%x, %loop]
+  %p2 = phi double [0.0, %entry], [%y, %loop]
+  %addr2 = getelementptr double* %q, i32 1
+  %addr = getelementptr double* %p, i32 1
+  store double %p1, double* %q
+  store double %p2, double* %addr2
+
+  %x = load double* %p
+  %y = load double* %addr
+  br label %loop
+}