[llvm] r290037 - Add custom type for PseudoSourceValue

Tom Stellard via llvm-commits llvm-commits at lists.llvm.org
Fri Dec 16 20:41:54 PST 2016

Author: tstellar
Date: Fri Dec 16 22:41:53 2016
New Revision: 290037

URL: http://llvm.org/viewvc/llvm-project?rev=290037&view=rev
Add custom type for PseudoSourceValue

PseudoSourceValue can be used to attach a target specific value for "well behaved" side-effects lowered from target specific intrinsics.
This is useful whenever there is not an LLVM IR Value around when representing such "well behaved" side-effected operations in backends by attaching a MachineMemOperand with a custom PseudoSourceValue as this makes the scheduler not treating them as "GlobalMemoryObjects" which triggers a logic that makes the operation act like a barrier in the Schedule DAG.

This patch adds another Kind to the PseudoSourceValue object which is "TargetCustom". It indicates a type of PseudoSourceValue that has a target specific meaning (aka. LLVM shouldn't assume any specific usage for such a PSV).

It supports the possibility of having many different kinds of "TargetCustom" PseudoSourceValues.

We had a discussion about if this was valuable or not (in particular because there was a believe that PSV were going away sooner or later) but seems like they are not going anywhere and I think they are useful backend side.

It is not clear the interaction of this with MIRParser (do we need a target hook to parse these?) and I would like a comment from Alex about that :)

Reviewers: arphaman, hfinkel, arsenm

Subscribers: Eugene.Zelenko, llvm-commits

Patch By: Marcello Maggioni

Differential Revision: https://reviews.llvm.org/D13575


Modified: llvm/trunk/include/llvm/CodeGen/PseudoSourceValue.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/CodeGen/PseudoSourceValue.h?rev=290037&r1=290036&r2=290037&view=diff
--- llvm/trunk/include/llvm/CodeGen/PseudoSourceValue.h (original)
+++ llvm/trunk/include/llvm/CodeGen/PseudoSourceValue.h Fri Dec 16 22:41:53 2016
@@ -42,7 +42,8 @@ public:
-    ExternalSymbolCallEntry
+    ExternalSymbolCallEntry,
+    TargetCustom
@@ -67,6 +68,9 @@ public:
   bool isGOT() const { return Kind == GOT; }
   bool isConstantPool() const { return Kind == ConstantPool; }
   bool isJumpTable() const { return Kind == JumpTable; }
+  unsigned getTargetCustom() const {
+    return (Kind >= TargetCustom) ? ((Kind+1) - TargetCustom) : 0;
+  }
   /// Test whether the memory pointed to by this PseudoSourceValue has a
   /// constant value.

Modified: llvm/trunk/lib/CodeGen/MIRPrinter.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/MIRPrinter.cpp?rev=290037&r1=290036&r2=290037&view=diff
--- llvm/trunk/lib/CodeGen/MIRPrinter.cpp (original)
+++ llvm/trunk/lib/CodeGen/MIRPrinter.cpp Fri Dec 16 22:41:53 2016
@@ -960,6 +960,9 @@ void MIPrinter::print(const MachineMemOp
           OS, cast<ExternalSymbolPseudoSourceValue>(PVal)->getSymbol());
+    case PseudoSourceValue::TargetCustom:
+      llvm_unreachable("TargetCustom pseudo source values are not supported");
+      break;

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