DAG: move sret demotion into most basic LowerCallTo implementation.

It looks like there are two versions of LowerCallTo here: the
SelectionDAGBuilder one is designed to operate on LLVM IR, and the
TargetLowering one in the case where everything is at DAG level.

Previously, only the SelectionDAGBuilder variant could handle demoting
an impossible return to sret semantics (before delegating to the
TargetLowering version), but this functionality is also useful for
certain libcalls (e.g. 128-bit operations on 32-bit x86).  So this
commit moves the sret handling down a level.

rdar://problem/17242889

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@211155 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 28 insertions, 0 deletions

diff --git a/test/CodeGen/X86/libcall-sret.ll b/test/CodeGen/X86/libcall-sret.ll
new file mode 100644
index 0000000000..67b99ac239
--- /dev/null
+++ b/test/CodeGen/X86/libcall-sret.ll
@@ -0,0 +1,28 @@
+; RUN: llc -mtriple=i686-linux-gnu -o - %s | FileCheck %s
+
+@var = global i128 0
+
+; We were trying to convert the i128 operation into a libcall, but failing to
+; perform sret demotion when we couldn't return the result in registers. Make
+; sure we marshal the return properly:
+
+define void @test_sret_libcall(i128 %l, i128 %r) {
+; CHECK-LABEL: test_sret_libcall:
+
+  ; Stack for call: 4(sret ptr), 16(i128 %l), 16(128 %r). So next logical
+  ; (aligned) place for the actual sret data is %esp + 40.
+; CHECK: leal 40(%esp), [[SRET_ADDR:%[a-z]+]]
+; CHECK: movl [[SRET_ADDR]], (%esp)
+; CHECK: calll __multi3
+; CHECK-DAG: movl 40(%esp), [[RES0:%[a-z]+]]
+; CHECK-DAG: movl 44(%esp), [[RES1:%[a-z]+]]
+; CHECK-DAG: movl 48(%esp), [[RES2:%[a-z]+]]
+; CHECK-DAG: movl 52(%esp), [[RES3:%[a-z]+]]
+; CHECK-DAG: movl [[RES0]], var
+; CHECK-DAG: movl [[RES1]], var+4
+; CHECK-DAG: movl [[RES2]], var+8
+; CHECK-DAG: movl [[RES3]], var+12
+  %prod = mul i128 %l, %r
+  store i128 %prod, i128* @var
+  ret void
+}