[PATCH] D102700: [Attributor] Change AAExecutionDomain to only accept intrinsics

[Joseph Huber via Phabricator via llvm-commits]

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The OpenMP runtime functions don't always provide unique thread ID's to
determine if a basic block is truly single-threaded. Change the implementation
to only check NVPTX intrinsics for now.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D102700

Files:
  llvm/lib/Transforms/IPO/OpenMPOpt.cpp
  llvm/test/Transforms/OpenMP/single_threaded_execution.ll


Index: llvm/test/Transforms/OpenMP/single_threaded_execution.ll
===================================================================
--- llvm/test/Transforms/OpenMP/single_threaded_execution.ll
+++ llvm/test/Transforms/OpenMP/single_threaded_execution.ll
@@ -2,12 +2,6 @@
 ; REQUIRES: asserts
 ; ModuleID = 'single_threaded_exeuction.c'
 
-%struct.ident_t = type { i32, i32, i32, i32, i8* }
-
- at .str = private unnamed_addr constant [4 x i8] c"%d\0A\00", align 1
- at 0 = private unnamed_addr constant [23 x i8] c";unknown;unknown;0;0;;\00", align 1
- at 1 = private unnamed_addr constant %struct.ident_t { i32 0, i32 2, i32 0, i32 0, i8* getelementptr inbounds ([23 x i8], [23 x i8]* @0, i32 0, i32 0) }, align 8
-
 ; CHECK: [openmp-opt] Basic block @bar entry is executed by a single thread.
 ; Function Attrs: noinline nounwind uwtable
 define internal void @bar() {
@@ -21,7 +15,8 @@
 ; Function Attrs: noinline nounwind uwtable
 define dso_local void @foo() {
 entry:
-  %call = call i32 @omp_get_thread_num()
+  %dummy = call i32 @omp_get_thread_num()
+  %call = call i32 @llvm.nvvm.read.ptx.sreg.tid.x()
   %cmp = icmp eq i32 %call, 0
   br i1 %cmp, label %if.then, label %if.end
 
@@ -35,6 +30,8 @@
 
 declare dso_local i32 @omp_get_thread_num()
 
+declare i32 @llvm.nvvm.read.ptx.sreg.tid.x()
+
 !llvm.module.flags = !{!0}
 !llvm.ident = !{!1}
 
Index: llvm/lib/Transforms/IPO/OpenMPOpt.cpp
===================================================================
--- llvm/lib/Transforms/IPO/OpenMPOpt.cpp
+++ llvm/lib/Transforms/IPO/OpenMPOpt.cpp
@@ -30,6 +30,8 @@
 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
 #include "llvm/Transforms/Utils/CallGraphUpdater.h"
 #include "llvm/Transforms/Utils/CodeExtractor.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/IntrinsicsNVPTX.h"
 
 using namespace llvm;
 using namespace omp;
@@ -2329,7 +2331,6 @@
 };
 
 ChangeStatus AAExecutionDomainFunction::updateImpl(Attributor &A) {
-  auto &OMPInfoCache = static_cast<OMPInformationCache &>(A.getInfoCache());
   Function *F = getAnchorScope();
   ReversePostOrderTraversal<Function *> RPOT(F);
   auto NumSingleThreadedBBs = SingleThreadedBBs.size();
@@ -2365,17 +2366,9 @@
     if (!C || !C->isZero())
       return false;
 
-    if (auto *CB = dyn_cast<CallBase>(Cmp->getOperand(0))) {
-      RuntimeFunction ThreadNumRuntimeIDs[] = {OMPRTL_omp_get_thread_num,
-                                               OMPRTL___kmpc_master,
-                                               OMPRTL___kmpc_global_thread_num};
-
-      for (const auto ThreadNumRuntimeID : ThreadNumRuntimeIDs) {
-        auto &RFI = OMPInfoCache.RFIs[ThreadNumRuntimeID];
-        if (CB->getCalledFunction() == RFI.Declaration)
-          return true;
-      }
-    }
+    if (auto *II = dyn_cast<IntrinsicInst>(Cmp->getOperand(0)))
+      if (II->getIntrinsicID() == Intrinsic::nvvm_read_ptx_sreg_tid_x)
+        return true;
 
     return false;
   };


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