[XCore] Target optimized library function __memcpy_4()

Summary:
If the src, dst and size of a memcpy are known to be 4 byte aligned we
can call __memcpy_4() instead of memcpy().

Reviewers: robertlytton

Reviewed By: robertlytton

CC: llvm-commits

Differential Revision: http://llvm-reviews.chandlerc.com/D2871

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@202395 91177308-0d34-0410-b5e6-96231b3b80d8

test/CodeGen/XCore/byVal.ll

@@ -20,7 +20,7 @@ entry:
 ; CHECK: ldaw r5, sp[1]
 ; CHECK: ldc r2, 40
 ; CHECK: mov r0, r5
-; CHECK: bl memcpy
+; CHECK: bl __memcpy_4
 ; CHECK: mov r0, r5
 ; CHECK: bl f1
 ; CHECK: mov r0, r4

test/CodeGen/XCore/memcpy.ll

@@ -0,0 +1,32 @@
+; RUN: llc < %s -march=xcore | FileCheck %s
+
+; Optimize memcpy to __memcpy_4 if src, dst and size are all 4 byte aligned.
+define void @f1(i8* %dst, i8* %src, i32 %n) nounwind {
+; CHECK-LABEL: f1:
+; CHECK: bl __memcpy_4
+entry:
+  %0 = shl i32 %n, 2
+  call void @llvm.memcpy.p0i8.p0i8.i32(i8* %dst, i8* %src, i32 %0, i32 4, i1 false)
+  ret void
+}
+
+; Can't optimize - size is not a multiple of 4.
+define void @f2(i8* %dst, i8* %src, i32 %n) nounwind {
+; CHECK-LABEL: f2:
+; CHECK: bl memcpy
+entry:
+  call void @llvm.memcpy.p0i8.p0i8.i32(i8* %dst, i8* %src, i32 %n, i32 4, i1 false)
+  ret void
+}
+
+; Can't optimize - alignment is not a multiple of 4.
+define void @f3(i8* %dst, i8* %src, i32 %n) nounwind {
+; CHECK-LABEL: f3:
+; CHECK: bl memcpy
+entry:
+  %0 = shl i32 %n, 2
+  call void @llvm.memcpy.p0i8.p0i8.i32(i8* %dst, i8* %src, i32 %0, i32 2, i1 false)
+  ret void
+}
+
+declare void @llvm.memcpy.p0i8.p0i8.i32(i8* nocapture, i8* nocapture, i32, i32, i1) nounwind