Implement an x86-64 ABI detail of passing structs by hidden first

argument. The x86-64 ABI requires the incoming value of %rdi to
be copied to %rax on exit from a function that is returning a
large C struct.

Also, add a README-X86-64 entry detailing the missed optimization
opportunity and proposing an alternative approach.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@50075 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 54 insertions, 0 deletions

diff --git a/test/CodeGen/X86/x86-64-sret-return.ll b/test/CodeGen/X86/x86-64-sret-return.ll
new file mode 100644
index 0000000..92986619
--- /dev/null
+++ b/test/CodeGen/X86/x86-64-sret-return.ll
@@ -0,0 +1,54 @@
+; RUN: llvm-as < %s | llc | grep {movq	%rdi, %rax}
+
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128"
+target triple = "x86_64-apple-darwin8"
+	%struct.foo = type { [4 x i64] }
+
+define void @bar(%struct.foo* noalias sret  %agg.result, %struct.foo* %d) nounwind  {
+entry:
+	%d_addr = alloca %struct.foo*		; <%struct.foo**> [#uses=2]
+	%memtmp = alloca %struct.foo, align 8		; <%struct.foo*> [#uses=1]
+	%"alloca point" = bitcast i32 0 to i32		; <i32> [#uses=0]
+	store %struct.foo* %d, %struct.foo** %d_addr
+	%tmp = load %struct.foo** %d_addr, align 8		; <%struct.foo*> [#uses=1]
+	%tmp1 = getelementptr %struct.foo* %agg.result, i32 0, i32 0		; <[4 x i64]*> [#uses=4]
+	%tmp2 = getelementptr %struct.foo* %tmp, i32 0, i32 0		; <[4 x i64]*> [#uses=4]
+	%tmp3 = getelementptr [4 x i64]* %tmp1, i32 0, i32 0		; <i64*> [#uses=1]
+	%tmp4 = getelementptr [4 x i64]* %tmp2, i32 0, i32 0		; <i64*> [#uses=1]
+	%tmp5 = load i64* %tmp4, align 8		; <i64> [#uses=1]
+	store i64 %tmp5, i64* %tmp3, align 8
+	%tmp6 = getelementptr [4 x i64]* %tmp1, i32 0, i32 1		; <i64*> [#uses=1]
+	%tmp7 = getelementptr [4 x i64]* %tmp2, i32 0, i32 1		; <i64*> [#uses=1]
+	%tmp8 = load i64* %tmp7, align 8		; <i64> [#uses=1]
+	store i64 %tmp8, i64* %tmp6, align 8
+	%tmp9 = getelementptr [4 x i64]* %tmp1, i32 0, i32 2		; <i64*> [#uses=1]
+	%tmp10 = getelementptr [4 x i64]* %tmp2, i32 0, i32 2		; <i64*> [#uses=1]
+	%tmp11 = load i64* %tmp10, align 8		; <i64> [#uses=1]
+	store i64 %tmp11, i64* %tmp9, align 8
+	%tmp12 = getelementptr [4 x i64]* %tmp1, i32 0, i32 3		; <i64*> [#uses=1]
+	%tmp13 = getelementptr [4 x i64]* %tmp2, i32 0, i32 3		; <i64*> [#uses=1]
+	%tmp14 = load i64* %tmp13, align 8		; <i64> [#uses=1]
+	store i64 %tmp14, i64* %tmp12, align 8
+	%tmp15 = getelementptr %struct.foo* %memtmp, i32 0, i32 0		; <[4 x i64]*> [#uses=4]
+	%tmp16 = getelementptr %struct.foo* %agg.result, i32 0, i32 0		; <[4 x i64]*> [#uses=4]
+	%tmp17 = getelementptr [4 x i64]* %tmp15, i32 0, i32 0		; <i64*> [#uses=1]
+	%tmp18 = getelementptr [4 x i64]* %tmp16, i32 0, i32 0		; <i64*> [#uses=1]
+	%tmp19 = load i64* %tmp18, align 8		; <i64> [#uses=1]
+	store i64 %tmp19, i64* %tmp17, align 8
+	%tmp20 = getelementptr [4 x i64]* %tmp15, i32 0, i32 1		; <i64*> [#uses=1]
+	%tmp21 = getelementptr [4 x i64]* %tmp16, i32 0, i32 1		; <i64*> [#uses=1]
+	%tmp22 = load i64* %tmp21, align 8		; <i64> [#uses=1]
+	store i64 %tmp22, i64* %tmp20, align 8
+	%tmp23 = getelementptr [4 x i64]* %tmp15, i32 0, i32 2		; <i64*> [#uses=1]
+	%tmp24 = getelementptr [4 x i64]* %tmp16, i32 0, i32 2		; <i64*> [#uses=1]
+	%tmp25 = load i64* %tmp24, align 8		; <i64> [#uses=1]
+	store i64 %tmp25, i64* %tmp23, align 8
+	%tmp26 = getelementptr [4 x i64]* %tmp15, i32 0, i32 3		; <i64*> [#uses=1]
+	%tmp27 = getelementptr [4 x i64]* %tmp16, i32 0, i32 3		; <i64*> [#uses=1]
+	%tmp28 = load i64* %tmp27, align 8		; <i64> [#uses=1]
+	store i64 %tmp28, i64* %tmp26, align 8
+	br label %return
+
+return:		; preds = %entry
+	ret void
+}