From 56ec9f2c09afebc42ecf243eaaab598daa15957b Mon Sep 17 00:00:00 2001
From: Akira Hatanaka <ahatanaka@mips.com>
Date: Wed, 9 May 2012 01:38:13 +0000
Subject: [PATCH] Make register FP allocatable if the compiled function does
 not have dynamic allocas.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@156458 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Target/Mips/MipsRegisterInfo.cpp | 10 +++++--
 test/CodeGen/Mips/fp-spill-reload.ll | 39 ++++++++++++++++++++++++++++
 2 files changed, 47 insertions(+), 2 deletions(-)
 create mode 100644 test/CodeGen/Mips/fp-spill-reload.ll

diff --git a/lib/Target/Mips/MipsRegisterInfo.cpp b/lib/Target/Mips/MipsRegisterInfo.cpp
index 952666301ac..aa632235d2d 100644
--- a/lib/Target/Mips/MipsRegisterInfo.cpp
+++ b/lib/Target/Mips/MipsRegisterInfo.cpp
@@ -85,12 +85,12 @@ BitVector MipsRegisterInfo::
 getReservedRegs(const MachineFunction &MF) const {
   static const uint16_t ReservedCPURegs[] = {
     Mips::ZERO, Mips::AT, Mips::K0, Mips::K1,
-    Mips::SP, Mips::FP, Mips::RA
+    Mips::SP, Mips::RA
   };
 
   static const uint16_t ReservedCPU64Regs[] = {
     Mips::ZERO_64, Mips::AT_64, Mips::K0_64, Mips::K1_64,
-    Mips::SP_64, Mips::FP_64, Mips::RA_64
+    Mips::SP_64, Mips::RA_64
   };
 
   BitVector Reserved(getNumRegs());
@@ -124,6 +124,12 @@ getReservedRegs(const MachineFunction &MF) const {
     Reserved.set(Mips::GP_64);
   }
 
+  // If this function has dynamic allocas, reserve FP.
+  if (MF.getTarget().getFrameLowering()->hasFP(MF)) {
+    Reserved.set(Mips::FP);
+    Reserved.set(Mips::FP_64);
+  }
+
   // Reserve hardware registers.
   Reserved.set(Mips::HWR29);
   Reserved.set(Mips::HWR29_64);
diff --git a/test/CodeGen/Mips/fp-spill-reload.ll b/test/CodeGen/Mips/fp-spill-reload.ll
new file mode 100644
index 00000000000..f9887a55827
--- /dev/null
+++ b/test/CodeGen/Mips/fp-spill-reload.ll
@@ -0,0 +1,39 @@
+; RUN: llc -march=mipsel < %s | FileCheck %s
+; check that $fp is not reserved. 
+
+define void @foo0(i32* nocapture %b) nounwind {
+entry:
+; CHECK: sw  $fp
+; CHECK: lw  $fp
+  %0 = load i32* %b, align 4
+  %arrayidx.1 = getelementptr inbounds i32* %b, i32 1
+  %1 = load i32* %arrayidx.1, align 4
+  %add.1 = add nsw i32 %1, 1
+  %arrayidx.2 = getelementptr inbounds i32* %b, i32 2
+  %2 = load i32* %arrayidx.2, align 4
+  %add.2 = add nsw i32 %2, 2
+  %arrayidx.3 = getelementptr inbounds i32* %b, i32 3
+  %3 = load i32* %arrayidx.3, align 4
+  %add.3 = add nsw i32 %3, 3
+  %arrayidx.4 = getelementptr inbounds i32* %b, i32 4
+  %4 = load i32* %arrayidx.4, align 4
+  %add.4 = add nsw i32 %4, 4
+  %arrayidx.5 = getelementptr inbounds i32* %b, i32 5
+  %5 = load i32* %arrayidx.5, align 4
+  %add.5 = add nsw i32 %5, 5
+  %arrayidx.6 = getelementptr inbounds i32* %b, i32 6
+  %6 = load i32* %arrayidx.6, align 4
+  %add.6 = add nsw i32 %6, 6
+  %arrayidx.7 = getelementptr inbounds i32* %b, i32 7
+  %7 = load i32* %arrayidx.7, align 4
+  %add.7 = add nsw i32 %7, 7
+  call void @foo2(i32 %0, i32 %add.1, i32 %add.2, i32 %add.3, i32 %add.4, i32 %add.5, i32 %add.6, i32 %add.7) nounwind
+  call void bitcast (void (...)* @foo1 to void ()*)() nounwind
+  call void @foo2(i32 %0, i32 %add.1, i32 %add.2, i32 %add.3, i32 %add.4, i32 %add.5, i32 %add.6, i32 %add.7) nounwind
+  ret void
+}
+
+declare void @foo2(i32, i32, i32, i32, i32, i32, i32, i32)
+
+declare void @foo1(...)
+