[AMDGPU] Added target-specific attribute amdgpu-max-memory-clause

With LLPC, previous investigation has suggested that si-scheduler
interacts badly with SiFormMemoryClauses on an XNACK target in some
games.

That needs further investigation in the future. In the meantime, this
commit adds a target-specific attribute to allow us to disable
SIFormMemoryClauses by setting it to 1 on a per-function basis for LLPC
to use.

Differential Revision: https://reviews.llvm.org/D62572

Change-Id: Ia0ca12ce79093cbbe86caded723ffb13384ede92
llvm-svn: 362127

1 files changed, 3 insertions, 1 deletions

diff --git a/llvm/lib/Target/AMDGPU/SIFormMemoryClauses.cpp b/llvm/lib/Target/AMDGPU/SIFormMemoryClauses.cpp
index 2cbed99beb2..f3c9ad63a80 100644
--- a/llvm/lib/Target/AMDGPU/SIFormMemoryClauses.cpp
+++ b/llvm/lib/Target/AMDGPU/SIFormMemoryClauses.cpp
@@ -319,6 +319,8 @@ bool SIFormMemoryClauses::runOnMachineFunction(MachineFunction &MF) {
 
   MaxVGPRs = TRI->getAllocatableSet(MF, &AMDGPU::VGPR_32RegClass).count();
   MaxSGPRs = TRI->getAllocatableSet(MF, &AMDGPU::SGPR_32RegClass).count();
+  unsigned FuncMaxClause = AMDGPU::getIntegerAttribute(
+      MF.getFunction(), "amdgpu-max-memory-clause", MaxClause);
 
   for (MachineBasicBlock &MBB : MF) {
     MachineBasicBlock::instr_iterator Next;
@@ -339,7 +341,7 @@ bool SIFormMemoryClauses::runOnMachineFunction(MachineFunction &MF) {
         continue;
 
       unsigned Length = 1;
-      for ( ; Next != E && Length < MaxClause; ++Next) {
+      for ( ; Next != E && Length < FuncMaxClause; ++Next) {
         if (!isValidClauseInst(*Next, IsVMEM))
           break;