[AMDGPU] Add safe-smem-prefetch SubtargetFeature off by default (#130050)

S_PREFETCH_* instructions may cause host to terminate process in case of
the invalid address.

Co-authored-by: Stanislav Mekhanoshin <[email protected]>

Author: mariusz-sikora-at-amd

llvm/lib/Target/AMDGPU/AMDGPU.td

@@ -244,6 +244,12 @@ def FeatureInstFwdPrefetchBug : SubtargetFeature<"inst-fwd-prefetch-bug",
   "S_INST_PREFETCH instruction causes shader to hang"
 >;
 
+def FeatureSafeSmemPrefetch : SubtargetFeature<"safe-smem-prefetch",
+  "HasSafeSmemPrefetch",
+  "true",
+  "SMEM prefetches do not fail on illegal address"
+>;
+
 def FeatureVcmpxExecWARHazard : SubtargetFeature<"vcmpx-exec-war-hazard",
   "HasVcmpxExecWARHazard",
   "true",

llvm/lib/Target/AMDGPU/AMDGPURegisterBankInfo.cpp

@@ -3460,7 +3460,7 @@ void AMDGPURegisterBankInfo::applyMappingImpl(
     applyMappingMAD_64_32(B, OpdMapper);
     return;
   case AMDGPU::G_PREFETCH: {
-    if (!Subtarget.hasPrefetch()) {
+    if (!Subtarget.hasPrefetch() || !Subtarget.hasSafeSmemPrefetch()) {
       MI.eraseFromParent();
       return;
     }

llvm/lib/Target/AMDGPU/GCNSubtarget.h

@@ -233,6 +233,7 @@ class GCNSubtarget final : public AMDGPUGenSubtargetInfo,
   bool HasVMEMtoScalarWriteHazard = false;
   bool HasSMEMtoVectorWriteHazard = false;
   bool HasInstFwdPrefetchBug = false;
+  bool HasSafeSmemPrefetch = false;
   bool HasVcmpxExecWARHazard = false;
   bool HasLdsBranchVmemWARHazard = false;
   bool HasNSAtoVMEMBug = false;
@@ -963,6 +964,8 @@ class GCNSubtarget final : public AMDGPUGenSubtargetInfo,
 
   bool hasPrefetch() const { return GFX12Insts; }
 
+  bool hasSafeSmemPrefetch() const { return HasSafeSmemPrefetch; }
+
   // Has s_cmpk_* instructions.
   bool hasSCmpK() const { return getGeneration() < GFX12; }
 

llvm/lib/Target/AMDGPU/SIISelLowering.cpp

@@ -855,7 +855,7 @@ SITargetLowering::SITargetLowering(const TargetMachine &TM,
   if (Subtarget->hasMad64_32())
     setOperationAction({ISD::SMUL_LOHI, ISD::UMUL_LOHI}, MVT::i32, Custom);
 
-  if (Subtarget->hasPrefetch())
+  if (Subtarget->hasPrefetch() && Subtarget->hasSafeSmemPrefetch())
     setOperationAction(ISD::PREFETCH, MVT::Other, Custom);
 
   if (Subtarget->hasIEEEMinMax()) {