commit 6ff59a16a05d43fdda587ce600b5b42a63cf3d33
author Akira Hatanaka <ahatanaka@mips.com> Sat Sep 28 00:12:32 2013 +0000
committer Akira Hatanaka <ahatanaka@mips.com> Sat Sep 28 00:12:32 2013 +0000
tree 4a9693eab502c4dbff8219cf9e17ea009803e7e6
parent e5f32cf3207da58359a6e3aeeb5b01205645f710

[mips] Make sure loads from lazy-binding entries do not get CSE'd or hoisted out
of loops.

Previously, two consecutive calls to function "func" would result in the
following sequence of instructions:

1. load $16, %got(func)($gp) // load address of lazy-binding stub.
2. move $25, $16
3. jalr $25                  // jump to lazy-binding stub.
4. nop
5. move $25, $16
6. jalr $25                  // jump to lazy-binding stub again.

With this patch, the second call directly jumps to func's address, bypassing
the lazy-binding resolution routine:

1. load $25, %got(func)($gp) // load address of lazy-binding stub.
2. jalr $25                  // jump to lazy-binding stub.
3. nop
4. load $25, %got(func)($gp) // load resolved address of func.
5. jalr $25                  // directly jump to func.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@191591 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/Mips/Mips16ISelLowering.cpp

diff --git a/lib/Target/Mips/Mips16ISelLowering.cpp b/lib/Target/Mips/Mips16ISelLowering.cpp
index 89f3d3b..ab649bd 100644
--- a/lib/Target/Mips/Mips16ISelLowering.cpp
+++ b/lib/Target/Mips/Mips16ISelLowering.cpp
@@ -419,6 +419,8 @@
             bool IsPICCall, bool GlobalOrExternal, bool InternalLinkage,
             CallLoweringInfo &CLI, SDValue Callee, SDValue Chain) const {
   SelectionDAG &DAG = CLI.DAG;
+  MachineFunction &MF = DAG.getMachineFunction();
+  MipsFunctionInfo *FuncInfo = MF.getInfo<MipsFunctionInfo>();
   const char* Mips16HelperFunction = 0;
   bool NeedMips16Helper = false;
 
@@ -474,9 +476,10 @@
     if (NeedMips16Helper) {
       RegsToPass.push_front(std::make_pair(V0Reg, Callee));
       JumpTarget = DAG.getExternalSymbol(Mips16HelperFunction, getPointerTy());
-      JumpTarget = getAddrGlobal(cast<ExternalSymbolSDNode>(JumpTarget),
-                                 JumpTarget.getValueType(), DAG,
-                                 MipsII::MO_GOT);
+      ExternalSymbolSDNode *S = cast<ExternalSymbolSDNode>(JumpTarget);
+      JumpTarget = getAddrGlobal(S, JumpTarget.getValueType(), DAG,
+                                 MipsII::MO_GOT, Chain,
+                                 FuncInfo->callPtrInfo(S->getSymbol()));
     } else
       RegsToPass.push_front(std::make_pair((unsigned)Mips::T9, Callee));
   }