commit 96f492d7df9e2bc2f2d76afb4d26cd59574d969f
author Alex Bradbury <asb@lowrisc.org> Wed Jun 13 12:04:51 2018 +0000
committer Alex Bradbury <asb@lowrisc.org> Wed Jun 13 12:04:51 2018 +0000
tree 95a905fb52a40a687edc691f21cb0e5ac29c5a92
parent dc790dd5d0eda1a22388824bd518045bc57741c1

[RISCV] Add codegen support for atomic load/stores with RV32A

Fences are inserted according to table A.6 in the current draft of version 2.3
of the RISC-V Instruction Set Manual, which incorporates the memory model
changes and definitions contributed by the RISC-V Memory Consistency Model
task group.

Instruction selection failures will now occur for 8/16/32-bit atomicrmw and 
cmpxchg operations when targeting RV32IA until lowering for these operations 
is added in a follow-on patch.

Differential Revision: https://reviews.llvm.org/D47589

llvm-svn: 334591

llvm/lib/Target/RISCV/RISCVISelLowering.cpp

diff --git a/llvm/lib/Target/RISCV/RISCVISelLowering.cpp b/llvm/lib/Target/RISCV/RISCVISelLowering.cpp
index b98f057..dda26a7 100644
--- a/llvm/lib/Target/RISCV/RISCVISelLowering.cpp
+++ b/llvm/lib/Target/RISCV/RISCVISelLowering.cpp
@@ -137,8 +137,10 @@
   setOperationAction(ISD::BlockAddress, XLenVT, Custom);
   setOperationAction(ISD::ConstantPool, XLenVT, Custom);
 
-  // Atomic operations aren't suported in the base RV32I ISA.
-  setMaxAtomicSizeInBitsSupported(0);
+  if (Subtarget.hasStdExtA())
+    setMaxAtomicSizeInBitsSupported(Subtarget.getXLen());
+  else
+    setMaxAtomicSizeInBitsSupported(0);
 
   setBooleanContents(ZeroOrOneBooleanContent);
 
@@ -1553,3 +1555,21 @@
 
   return TargetLowering::getRegForInlineAsmConstraint(TRI, Constraint, VT);
 }
+
+Instruction *RISCVTargetLowering::emitLeadingFence(IRBuilder<> &Builder,
+                                                   Instruction *Inst,
+                                                   AtomicOrdering Ord) const {
+  if (isa<LoadInst>(Inst) && Ord == AtomicOrdering::SequentiallyConsistent)
+    return Builder.CreateFence(Ord);
+  if (isa<StoreInst>(Inst) && isReleaseOrStronger(Ord))
+    return Builder.CreateFence(AtomicOrdering::Release);
+  return nullptr;
+}
+
+Instruction *RISCVTargetLowering::emitTrailingFence(IRBuilder<> &Builder,
+                                                    Instruction *Inst,
+                                                    AtomicOrdering Ord) const {
+  if (isa<LoadInst>(Inst) && isAcquireOrStronger(Ord))
+    return Builder.CreateFence(AtomicOrdering::Acquire);
+  return nullptr;
+}