commit 80e107ccd088a2705d0e776799a8815a58061cb3
author Zequan Wu <zequanwu@google.com> Fri May 29 12:15:07 2020 -0700
committer Zequan Wu <zequanwu@google.com> Fri May 29 12:31:06 2020 -0700
tree f697f4807d0544468fbc8a9f219758837ad71d24
parent 6f56a586c505bd587106a9b94388d70efb88155b

Add NoMerge MIFlag to avoid MIR branch folding

Let the codegen recognized the nomerge attribute and disable branch folding when the attribute is given

Differential Revision: https://reviews.llvm.org/D79537

llvm/lib/CodeGen/BranchFolding.cpp

diff --git a/llvm/lib/CodeGen/BranchFolding.cpp b/llvm/lib/CodeGen/BranchFolding.cpp
index 852bfb3..df79019 100644
--- a/llvm/lib/CodeGen/BranchFolding.cpp
+++ b/llvm/lib/CodeGen/BranchFolding.cpp
@@ -348,6 +348,9 @@
         MBBI1->isInlineAsm()) {
       break;
     }
+    if (MBBI1->getFlag(MachineInstr::NoMerge) ||
+        MBBI2->getFlag(MachineInstr::NoMerge))
+      break;
     ++TailLen;
     I1 = MBBI1;
     I2 = MBBI2;

llvm/lib/CodeGen/MIRPrinter.cpp

diff --git a/llvm/lib/CodeGen/MIRPrinter.cpp b/llvm/lib/CodeGen/MIRPrinter.cpp
index 36cd39f2..fa23df6 100644
--- a/llvm/lib/CodeGen/MIRPrinter.cpp
+++ b/llvm/lib/CodeGen/MIRPrinter.cpp
@@ -778,6 +778,8 @@
     OS << "exact ";
   if (MI.getFlag(MachineInstr::NoFPExcept))
     OS << "nofpexcept ";
+  if (MI.getFlag(MachineInstr::NoMerge))
+    OS << "nomerge ";
 
   OS << TII->getName(MI.getOpcode());
   if (I < E)

llvm/lib/CodeGen/MachineInstr.cpp

diff --git a/llvm/lib/CodeGen/MachineInstr.cpp b/llvm/lib/CodeGen/MachineInstr.cpp
index 7afa61f..987de0c 100644
--- a/llvm/lib/CodeGen/MachineInstr.cpp
+++ b/llvm/lib/CodeGen/MachineInstr.cpp
@@ -1595,6 +1595,8 @@
     OS << "exact ";
   if (getFlag(MachineInstr::NoFPExcept))
     OS << "nofpexcept ";
+  if (getFlag(MachineInstr::NoMerge))
+    OS << "nomerge ";
 
   // Print the opcode name.
   if (TII)

llvm/lib/CodeGen/SelectionDAG/ScheduleDAGSDNodes.cpp

diff --git a/llvm/lib/CodeGen/SelectionDAG/ScheduleDAGSDNodes.cpp b/llvm/lib/CodeGen/SelectionDAG/ScheduleDAGSDNodes.cpp
index 83aaf93..731cd23 100644
--- a/llvm/lib/CodeGen/SelectionDAG/ScheduleDAGSDNodes.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/ScheduleDAGSDNodes.cpp
@@ -872,6 +872,10 @@
         DAG->getTarget().Options.EmitCallSiteInfo)
       MF.addCallArgsForwardingRegs(MI, DAG->getSDCallSiteInfo(Node));
 
+    if (DAG->getNoMergeSiteInfo(Node)) {
+      MI->setFlag(MachineInstr::MIFlag::NoMerge);
+    }
+
     return MI;
   };