[PPCGCodeGeneration] Correct usage of llvm::Value with getLatestValue.

It is possible that the `HostPtr` that coresponds to an array could be
invariant load hoisted. Make sure we use the invariant load hoisted
value by using `IslNodeBuilder::getLatestValue`.

Differential Revision: https://reviews.llvm.org/D36001

llvm-svn: 309681

polly/lib/CodeGen/PPCGCodeGeneration.cpp

@@ -1104,6 +1104,7 @@ Value *GPUNodeBuilder::getOrCreateManagedDeviceArray(gpu_array_info *Array,
       HostPtr = BlockGen.getOrCreateAlloca(ArrayInfo);
     else
       HostPtr = ArrayInfo->getBasePtr();
+    HostPtr = getLatestValue(HostPtr);
 
     Value *Offset = getArrayOffset(Array);
     if (Offset) {
@@ -1137,6 +1138,7 @@ void GPUNodeBuilder::createDataTransfer(__isl_take isl_ast_node *TransferStmt,
     HostPtr = BlockGen.getOrCreateAlloca(ScopArray);
   else
     HostPtr = ScopArray->getBasePtr();
+  HostPtr = getLatestValue(HostPtr);
 
   if (Offset) {
     HostPtr = Builder.CreatePointerCast(

polly/test/GPGPU/invariant-load-hoisting-of-array.ll

@@ -0,0 +1,100 @@
+; RUN: opt %loadPolly -analyze -polly-scops \
+; RUN: -polly-invariant-load-hoisting < %s | FileCheck %s -check-prefix=SCOP
+
+; RUN: opt %loadPolly -S -polly-codegen-ppcg \
+; RUN: -polly-invariant-load-hoisting < %s | FileCheck %s -check-prefix=HOST-IR
+
+; Entry: Contains (%loaded.ptr.preload.s2a = alloca double*) which is
+;   |    invariant load hoisted `%loaded.ptr`
+;   v
+; Run-time check --(failure branch)--> { old code - contains `%loaded.ptr` }
+;   |
+;  (success branch)
+;   |
+;   v
+; New Code: Should refer to `%loaded.ptr.preload.s2a`, which is
+;           the invariant load hoisted value, NOT `%loaded.ptr`.
+
+; In Polly, we preserve the old code and create a separate branch that executes
+; the GPU code if a run-time check succeeds.
+
+; We need to make sure that in the new branch, we pick up invariant load hoisted
+; values. The old values will belong to the old code branch.
+
+; In this case, we use to try to load the 'original' %loaded.ptr in the
+; 'New Code' branch,which is wrong. Check that this does not happen.
+
+; Check that we have a Scop with an invariant load of the array.
+; SCOP:       Function: f
+; SCOP-NEXT:  Region: %arrload---%for.exit
+; SCOP-NEXT:  Max Loop Depth:  1
+; SCOP-NEXT:  Invariant Accesses: {
+; SCOP-NEXT:          ReadAccess :=	[Reduction Type: NONE] [Scalar: 0]
+; SCOP-NEXT:              { Stmt_arrload[] -> MemRef_arr_of_ptrs[0] };
+
+
+
+; Check that we have the preloaded array.
+; HOST-IR: entry:
+; HOST-IR-NEXT:  %loaded.ptr.preload.s2a = alloca double*
+
+; Chek that we store the correct value in the preload.
+; polly.preload.begin:                              ; preds = %polly.split_new_and_old
+; HOST-IR: %polly.access.arr.of.ptrs = getelementptr double*, double** %arr.of.ptrs, i64 0
+; HOST-IR-NEXT: %polly.access.arr.of.ptrs.load = load double*, double** %polly.access.arr.of.ptrs
+; HOST-IR-NEXT: store double* %polly.access.arr.of.ptrs.load, double** %loaded.ptr.preload.s2a
+
+; Check that we get back data from the kernel.
+; HOST-IR: polly.acc.initialize:                             ; preds = %polly.start
+; HOST-IR: [[FIRSTINDEX:%.+]] = getelementptr double, double* %polly.access.arr.of.ptrs.load, i64 1
+; HOST-IR: [[BITCASTED:%.+]] = bitcast double* [[FIRSTINDEX]] to i8*
+; HOST-IR: call void @polly_copyFromDeviceToHost(i8* %p_dev_array_MemRef_loaded_ptr, i8* [[BITCASTED]], i64 800)
+
+; Check that the kernel launch is generated in the host IR.
+; This declaration would not have been generated unless a kernel launch exists.
+; HOST-IR: declare void @polly_launchKernel(i8*, i32, i32, i32, i32, i32, i8*)
+
+
+; C pseudocode equivalent
+; void f(double **arr_of_ptrs) {
+;     double *loaded_ptr = arr_of_ptrs[0];
+;     if (false) { return; }
+;     else {
+;         for(int i = 1; i < 100; i++) {
+;             loaded_ptr[i] = 42.0;
+;         }
+;     }
+; }
+
+
+target datalayout = "e-p:64:64:64-S128-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f16:16:16-f32:32:32-f64:64:64-f128:128:128-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64"
+target triple = "x86_64-unknown-linux-gnu"
+
+
+; Function Attrs: nounwind uwtable
+define void @f(double **%arr.of.ptrs) #0 {
+entry:
+  br label %arrload
+
+arrload:                                             ; preds = %"7"
+  %loaded.ptr = load double*, double** %arr.of.ptrs, align 8
+  br i1 false, label %"for.exit", label %"for.preheader"
+
+"for.preheader":                                       ; preds = %"51"
+  br label %"for.body"
+
+"for.body":                                             ; preds = %"53", %"53.lr.ph"
+  %indvar = phi i64 [ 1, %"for.preheader" ], [ %indvar.next, %"for.body" ]
+  %slot = getelementptr double, double* %loaded.ptr, i64 %indvar
+  store double 42.0, double* %slot, align 8
+
+  %indvar.next = add nuw nsw i64 %indvar, 1
+
+  %check = icmp sgt i64 %indvar.next, 100
+  br i1 %check, label %"for.exit", label %"for.body"
+
+"for.exit":                                             ; preds = %"52.54_crit_edge", %"51"
+    ret void
+}
+
+attributes #0 = { nounwind uwtable }