From abc7f410e90ad61d70dabfb030edcec25472c21a Mon Sep 17 00:00:00 2001
From: Simon Dardis <simon.dardis@imgtec.com>
Date: Wed, 21 Sep 2016 09:43:40 +0000
Subject: [PATCH] [mips] LLVM PR/30197 - Tail call incorrectly clobbers
 arguments for mips

The postRA scheduler performs alias analysis to determine if stores and loads
can moved past each other. When a function has more arguments than argument
registers for the calling convention used, excess arguments are spilled onto the
stack. LLVM by default assumes that argument slots are immutable, unless the
function contains a tail call. Without the knowledge of that a function contains
a tail call site, stores and loads to fixed stack slots may be re-ordered
causing the out-going arguments to clobber the incoming arguments before the
incoming arguments are supposed to be dead.

Reviewers: vkalintiris

Differential Review: https://reviews.llvm.org/D24077



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@282063 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Target/Mips/MipsISelLowering.cpp          |  4 +-
 .../tailcall/tail-call-arguments-clobber.ll   | 53 +++++++++++++++++++
 2 files changed, 56 insertions(+), 1 deletion(-)
 create mode 100644 test/CodeGen/Mips/tailcall/tail-call-arguments-clobber.ll

diff --git a/lib/Target/Mips/MipsISelLowering.cpp b/lib/Target/Mips/MipsISelLowering.cpp
index 417eb8d9b80..fcd0450a067 100644
--- a/lib/Target/Mips/MipsISelLowering.cpp
+++ b/lib/Target/Mips/MipsISelLowering.cpp
@@ -2866,8 +2866,10 @@ MipsTargetLowering::LowerCall(TargetLowering::CallLoweringInfo &CLI,
   getOpndList(Ops, RegsToPass, IsPICCall, GlobalOrExternal, InternalLinkage,
               IsCallReloc, CLI, Callee, Chain);
 
-  if (IsTailCall)
+  if (IsTailCall) {
+    MF.getFrameInfo().setHasTailCall();
     return DAG.getNode(MipsISD::TailCall, DL, MVT::Other, Ops);
+  }
 
   Chain = DAG.getNode(MipsISD::JmpLink, DL, NodeTys, Ops);
   SDValue InFlag = Chain.getValue(1);
diff --git a/test/CodeGen/Mips/tailcall/tail-call-arguments-clobber.ll b/test/CodeGen/Mips/tailcall/tail-call-arguments-clobber.ll
new file mode 100644
index 00000000000..36691fd7a8d
--- /dev/null
+++ b/test/CodeGen/Mips/tailcall/tail-call-arguments-clobber.ll
@@ -0,0 +1,53 @@
+; RUN: llc -march=mips -mcpu=mips32 -O0 -relocation-model=pic < %s | FileCheck \
+; RUN:     %s -check-prefix=MIPS32
+; RUN: llc -march=mips64 -mcpu=mips64 -O0 -relocation-model=pic -target-abi n64 \
+; RUN:     < %s | FileCheck %s -check-prefix=MIPS64
+; RUN: llc -march=mips64 -mcpu=mips64 -O0 -relocation-model=pic -target-abi n32 \
+; RUN:     < %s | FileCheck %s -check-prefix=MIPS64
+
+
+; LLVM PR/30197
+; Test that the scheduler does not order loads and stores of arguments that
+; are passed on the stack such that the arguments of the caller are clobbered
+; too early.
+
+; This test is more fragile than I'd like. The -NEXT directives enforce an
+; assumption that any GOT related instructions will not appear between the
+; loads and stores.
+
+; O32 case: The last two arguments should appear at 16(sp), 20(sp). The order
+;           of the loads doesn't matter, but they have to become before the
+;           stores
+declare i32 @func2(i32, i32, i32, i32, i32, i32)
+
+define i32 @func1(i32 %a, i32 %b, i32 %c, i32 %d, i32 %e, i32 %f){
+
+; MIPS32: lw ${{[0-9]+}}, {{[0-9]+}}($sp)
+; MIPS32-NEXT: lw ${{[0-9]+}}, {{[0-9]+}}($sp)
+; MIPS32-NEXT: sw ${{[0-9]+}}, {{[0-9]+}}($sp)
+; MIPS32-NEXT: sw ${{[0-9]+}}, {{[0-9]+}}($sp)
+  %retval = tail call i32 @func1(i32 %a, i32 %f, i32 %c, i32 %d, i32 %e, i32 %b)
+
+  ret i32 %retval
+}
+
+; N64, N32 cases: N64 and N32 both pass 8 arguments in registers. The order
+;           of the loads doesn't matter, but they have to become before the
+;           stores
+
+declare i64 @func4(i64, i64, i64, i64, i64, i64, i64, i64, i64, i64)
+
+define i64 @func3(i64 %a, i64 %b, i64 %c, i64 %d,
+                  i64 %e, i64 %f, i64 %g, i64 %h,
+                  i64 %i, i64 %j){
+
+; MIPS64: ld ${{[0-9]+}}, {{[0-9]+}}($sp)
+; MIPS64-NEXT: ld ${{[0-9]+}}, {{[0-9]+}}($sp)
+; MIPS64-NEXT: sd ${{[0-9]+}}, {{[0-9]+}}($sp)
+; MIPS64-NEXT: sd ${{[0-9]+}}, {{[0-9]+}}($sp)
+  %retval = tail call i64 @func4(i64 %a, i64 %j, i64 %c, i64 %d, i64 %e, i64 %f, i64 %g, i64 %h, i64 %i, i64 %b)
+
+  ret i64 %retval
+}
+
+