[SROA] Fix GEP(Phi) unfolding when the GEP is inside a spawned task and the Phi is outside of that task.

Author: neboat

llvm/lib/Transforms/Scalar/SROA.cpp

@@ -4221,9 +4221,11 @@ class AggLoadStoreRewriter : public InstVisitor<AggLoadStoreRewriter, bool> {
 
     Type *SourceTy = GEPI.getSourceElementType();
     // We only handle arguments, constants, and static allocas here, so we can
-    // insert GEPs at the end of the entry block.
+    // insert GEPs at the end of the entry block of the task that contains both
+    // the GEP and the Phi.  Because the GEP uses the Phi, we use the Phi
+    // to determine which task contains both.
     IRB.SetInsertPoint(
-        TI->getTaskFor(GEPI.getParent())->getEntry()->getTerminator());
+        TI->getTaskFor(Phi->getParent())->getEntry()->getTerminator());
     for (unsigned I = 0, E = Phi->getNumIncomingValues(); I != E; ++I) {
       Value *Op = Phi->getIncomingValue(I);
       BasicBlock *BB = Phi->getIncomingBlock(I);

llvm/test/Transforms/Tapir/sroa-gep-insert-before-task.ll

@@ -0,0 +1,57 @@
+; Check that SROA unfolds gep(phi) appropriately when the gep is inside a task and the phi is outside of the task.
+;
+; RUN: opt < %s -passes="cgscc(devirt<4>(function<eager-inv;no-rerun>(sroa<modify-cfg>)))" -S | FileCheck %s
+
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+%"class.cv::Mat" = type { i32, i32, i32, i32, ptr, ptr, ptr, ptr, ptr, ptr, %"struct.cv::MatSize", %"struct.cv::MatStep" }
+%"struct.cv::MatSize" = type { ptr }
+%"struct.cv::MatStep" = type { ptr, [2 x i64] }
+
+define { ptr, i32 } @_ZN2cv5remapERKNS_11_InputArrayERKNS_12_OutputArrayES2_S2_iiRKNS_7Scalar_IdEE() personality ptr null {
+entry:
+  %map1 = alloca %"class.cv::Mat", align 8
+  %syncreg = call token @llvm.syncregion.start()
+  call void null(ptr %map1, ptr null)
+  br label %if.end451
+
+; CHECK: entry:
+; CHECK: %[[SROA_GEP:.+]] = getelementptr i8, ptr %map1, i64 16
+; CHECK: br label %if.end451
+
+if.end451:                                        ; preds = %entry
+  %0 = phi ptr [ %map1, %entry ]
+  br label %pfor.cond
+
+; CHECK: if.end451:
+; CHECK: %[[SROA_PHI:.+]] = phi ptr [ %[[SROA_GEP]], %entry ]
+; CHECK: br label %pfor.cond
+
+pfor.cond:                                        ; preds = %pfor.cond, %if.end451
+  detach within %syncreg, label %pfor.body.entry, label %pfor.cond unwind label %lpad889
+
+; CHECK: pfor.cond:
+; CHECK-NEXT: detach within %syncreg, label %pfor.body.entry,
+
+pfor.body.entry:                                  ; preds = %pfor.cond
+  %data.i466 = getelementptr i8, ptr %0, i64 16
+  br label %for.cond716
+
+; CHECK: pfor.body.entry:
+; CHECK-NOT: getelementptr
+; CHECK-NEXT: br label %for.cond716
+
+for.cond716:                                      ; preds = %for.cond716, %pfor.body.entry
+  br label %for.cond716
+
+lpad889:                                          ; preds = %pfor.cond
+  %1 = landingpad { ptr, i32 }
+          cleanup
+  ret { ptr, i32 } %1
+}
+
+; Function Attrs: nounwind willreturn memory(argmem: readwrite)
+declare token @llvm.syncregion.start() #0
+
+attributes #0 = { nounwind willreturn memory(argmem: readwrite) }