From 75475edb1f3f053d2de4a56e38378a7a3ef61204 Mon Sep 17 00:00:00 2001
From: Daniel Sanders <daniel.sanders@imgtec.com>
Date: Mon, 12 Oct 2015 13:55:44 +0000
Subject: [PATCH] [mips] Handle undef when extracting subregs from FP64
 registers.

Summary:
This removes unnecessary instructions when extracting from an undefined register
and also fixes a crash for O32 when passing undef to a double argument in
held in integer registers.

Reviewers: vkalintiris

Subscribers: llvm-commits, zoran.jovanovic, petarj

Differential Revision: http://reviews.llvm.org/D13467

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@250039 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Target/Mips/MipsSEFrameLowering.cpp | 16 ++++++++++++----
 test/CodeGen/Mips/llvm-ir/call.ll       | 14 ++++++++++++++
 2 files changed, 26 insertions(+), 4 deletions(-)

diff --git a/lib/Target/Mips/MipsSEFrameLowering.cpp b/lib/Target/Mips/MipsSEFrameLowering.cpp
index a516e947975..94885d680bb 100644
--- a/lib/Target/Mips/MipsSEFrameLowering.cpp
+++ b/lib/Target/Mips/MipsSEFrameLowering.cpp
@@ -319,6 +319,15 @@ bool ExpandPseudo::expandBuildPairF64(MachineBasicBlock &MBB,
 bool ExpandPseudo::expandExtractElementF64(MachineBasicBlock &MBB,
                                            MachineBasicBlock::iterator I,
                                            bool FP64) const {
+  const MachineOperand &Op1 = I->getOperand(1);
+  const MachineOperand &Op2 = I->getOperand(2);
+
+  if ((Op1.isReg() && Op1.isUndef()) || (Op2.isReg() && Op2.isUndef())) {
+    unsigned DstReg = I->getOperand(0).getReg();
+    BuildMI(MBB, I, I->getDebugLoc(), TII.get(Mips::IMPLICIT_DEF), DstReg);
+    return true;
+  }
+
   // For fpxx and when mfhc1 is not available, use:
   //   spill + reload via ldc1
   //
@@ -335,8 +344,8 @@ bool ExpandPseudo::expandExtractElementF64(MachineBasicBlock &MBB,
   if ((Subtarget.isABI_FPXX() && !Subtarget.hasMTHC1()) ||
       (FP64 && !Subtarget.useOddSPReg())) {
     unsigned DstReg = I->getOperand(0).getReg();
-    unsigned SrcReg = I->getOperand(1).getReg();
-    unsigned N = I->getOperand(2).getImm();
+    unsigned SrcReg = Op1.getReg();
+    unsigned N = Op2.getImm();
     int64_t Offset = 4 * (Subtarget.isLittle() ? N : (1 - N));
 
     // It should be impossible to have FGR64 on MIPS-II or MIPS32r1 (which are
@@ -352,8 +361,7 @@ bool ExpandPseudo::expandExtractElementF64(MachineBasicBlock &MBB,
     // We re-use the same spill slot each time so that the stack frame doesn't
     // grow too much in functions with a large number of moves.
     int FI = MF.getInfo<MipsFunctionInfo>()->getMoveF64ViaSpillFI(RC);
-    TII.storeRegToStack(MBB, I, SrcReg, I->getOperand(1).isKill(), FI, RC,
-                        &RegInfo, 0);
+    TII.storeRegToStack(MBB, I, SrcReg, Op1.isKill(), FI, RC, &RegInfo, 0);
     TII.loadRegFromStack(MBB, I, DstReg, FI, RC2, &RegInfo, Offset);
     return true;
   }
diff --git a/test/CodeGen/Mips/llvm-ir/call.ll b/test/CodeGen/Mips/llvm-ir/call.ll
index 112ab8ee8c7..6c4f08daee9 100644
--- a/test/CodeGen/Mips/llvm-ir/call.ll
+++ b/test/CodeGen/Mips/llvm-ir/call.ll
@@ -6,6 +6,7 @@
 ; RUN: llc -march=mips   -mcpu=mips32r3 -enable-mips-tail-calls < %s | FileCheck %s -check-prefix=ALL -check-prefix=O32
 ; RUN: llc -march=mips   -mcpu=mips32r5 -enable-mips-tail-calls < %s | FileCheck %s -check-prefix=ALL -check-prefix=O32
 ; RUN: llc -march=mips   -mcpu=mips32r6 -enable-mips-tail-calls < %s | FileCheck %s -check-prefix=ALL -check-prefix=O32
+; RUN: llc -march=mips   -mcpu=mips32r6 -mattr=+fp64,+nooddspreg -enable-mips-tail-calls < %s | FileCheck %s -check-prefix=ALL -check-prefix=O32
 ; RUN: llc -march=mips64 -mcpu=mips4    -enable-mips-tail-calls < %s | FileCheck %s -check-prefix=ALL -check-prefix=N64
 ; RUN: llc -march=mips64 -mcpu=mips64   -enable-mips-tail-calls < %s | FileCheck %s -check-prefix=ALL -check-prefix=N64
 ; RUN: llc -march=mips64 -mcpu=mips64r2 -enable-mips-tail-calls < %s | FileCheck %s -check-prefix=ALL -check-prefix=N64
@@ -168,3 +169,16 @@ define float @tail_indirect_call_float_void(float ()* %addr) {
   %1 = tail call float %addr()
   ret float %1
 }
+
+; Check that passing undef as a double value doesn't cause machine code errors
+; for FP64.
+declare hidden void @undef_double(i32 %this, double %volume) unnamed_addr align 2
+
+define hidden void @thunk_undef_double(i32 %this, double %volume) unnamed_addr align 2 {
+; ALL-LABEL: thunk_undef_double:
+; O32: # implicit-def: A2
+; O32: # implicit-def: A3
+; ALL: jr $25
+  tail call void @undef_double(i32 undef, double undef) #8
+  ret void
+}
-- 
2.34.1