[PATCH] D108971: [AMDGPU] Split entry basic block after alloca instructions.

[Mahesha S via Phabricator via llvm-commits]

hsmhsm created this revision.
hsmhsm added reviewers: arsenm, rampitec, foad.
Herald added subscribers: kerbowa, hiraditya, t-tye, tpr, dstuttard, yaxunl, nhaehnle, jvesely, kzhuravl.
hsmhsm requested review of this revision.
Herald added subscribers: llvm-commits, wdng.
Herald added a project: LLVM.

While initializing the LDS pointers within entry basic block of kernel(s), make
sure that the entry basic block is split after alloca instructions.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D108971

Files:
  llvm/lib/Target/AMDGPU/AMDGPUReplaceLDSUseWithPointer.cpp
  llvm/test/CodeGen/AMDGPU/replace-lds-by-ptr-split-entry-bb-after-alloca.ll


Index: llvm/test/CodeGen/AMDGPU/replace-lds-by-ptr-split-entry-bb-after-alloca.ll
===================================================================
--- /dev/null
+++ llvm/test/CodeGen/AMDGPU/replace-lds-by-ptr-split-entry-bb-after-alloca.ll
@@ -0,0 +1,61 @@
+; RUN: opt -S -mtriple=amdgcn--  -amdgpu-replace-lds-use-with-pointer -amdgpu-enable-lds-replace-with-pointer=true < %s | FileCheck %s
+
+; DESCRIPTION:
+;
+; There is one lds global defined here, and this lds is used within a single non-kernel
+; function, as an operand of nested constant expression, and this non-kernel function is
+; reachable from kernel. Hence nested constant expression should to be converted into a
+; series of instructons and pointer replacement should take place.
+;
+; Further the entry basic block of the kernel @k0 contains alloca instruction. Hence the
+; entry basic splitting for pointer initialization should happen after alloca.
+;
+
+; Original LDS should exist.
+; CHECK: @used_only_within_func = addrspace(3) global [4 x i32] undef, align 4
+ at used_only_within_func = addrspace(3) global [4 x i32] undef, align 4
+
+; Pointers should be created.
+; CHECK: @used_only_within_func.ptr = internal unnamed_addr addrspace(3) global i16 undef, align 2
+
+; Pointer replacement code should be added.
+define void @f0(i32 %x) {
+; CHECK-LABEL: entry:
+; CHECK:   %0 = load i16, i16 addrspace(3)* @used_only_within_func.ptr, align 2
+; CHECK:   %1 = getelementptr i8, i8 addrspace(3)* null, i16 %0
+; CHECK:   %2 = bitcast i8 addrspace(3)* %1 to [4 x i32] addrspace(3)*
+; CHECK:   %3 = getelementptr inbounds [4 x i32], [4 x i32] addrspace(3)* %2, i32 0, i32 0
+; CHECK:   %4 = addrspacecast i32 addrspace(3)* %3 to i32*
+; CHECK:   %5 = ptrtoint i32* %4 to i64
+; CHECK:   %6 = add i64 %5, %5
+; CHECK:   %7 = inttoptr i64 %6 to i32*
+; CHECK:   store i32 %x, i32* %7, align 4
+; CHECK:   ret void
+entry:
+  store i32 %x, i32* inttoptr (i64 add (i64 ptrtoint (i32* addrspacecast (i32 addrspace(3)* bitcast ([4 x i32] addrspace(3)* @used_only_within_func to i32 addrspace(3)*) to i32*) to i64), i64 ptrtoint (i32* addrspacecast (i32 addrspace(3)* bitcast ([4 x i32] addrspace(3)* @used_only_within_func to i32 addrspace(3)*) to i32*) to i64)) to i32*), align 4
+  ret void
+}
+
+; Pointer initialization code shoud be added
+define amdgpu_kernel void @k0() {
+; CHECK-LABEL: entry:
+; CHECK:   %0 = alloca i64, align 8, addrspace(5)
+; CHECK:   %1 = call i32 @llvm.amdgcn.mbcnt.lo(i32 -1, i32 0)
+; CHECK:   %2 = icmp eq i32 %1, 0
+; CHECK:   br i1 %2, label %3, label %4
+;
+; CHECK-LABEL: 3:
+; CHECK:   store i16 ptrtoint ([4 x i32] addrspace(3)* @used_only_within_func to i16), i16 addrspace(3)* @used_only_within_func.ptr, align 2
+; CHECK:   br label %4
+
+; CHECK-LABEL: 4:
+; CHECK:   call void @llvm.amdgcn.wave.barrier()
+; CHECK:   %5 = addrspacecast i64 addrspace(5)* %0 to i64*
+; CHECK:   call void @f0(i32 0)
+; CHECK:   ret void
+entry:
+  %0 = alloca i64, align 8, addrspace(5)
+  %1 = addrspacecast i64 addrspace(5)* %0 to i64*
+  call void @f0(i32 0)
+  ret void
+}
Index: llvm/lib/Target/AMDGPU/AMDGPUReplaceLDSUseWithPointer.cpp
===================================================================
--- llvm/lib/Target/AMDGPU/AMDGPUReplaceLDSUseWithPointer.cpp
+++ llvm/lib/Target/AMDGPU/AMDGPUReplaceLDSUseWithPointer.cpp
@@ -191,10 +191,19 @@
     if (!BasicBlockEntry.second)
       return BasicBlockEntry.first->second;
 
-    // Split entry basic block of kernel K.
-    auto *EI = &(*(K->getEntryBlock().getFirstInsertionPt()));
-    IRBuilder<> Builder(EI);
-
+    // Split entry basic block of kernel K just after alloca.
+    //
+    // Find the split point just after alloca.
+    auto &EBB = K->getEntryBlock();
+    auto *EI = &(*(EBB.getFirstInsertionPt()));
+    BasicBlock::reverse_iterator RIT(EBB.getTerminator());
+    while (!isa<AllocaInst>(*RIT) && (&*RIT != EI))
+      ++RIT;
+    if (isa<AllocaInst>(*RIT))
+      --RIT;
+
+    // Split entry basic block.
+    IRBuilder<> Builder(&*RIT);
     Value *Mbcnt =
         Builder.CreateIntrinsic(Intrinsic::amdgcn_mbcnt_lo, {},
                                 {Builder.getInt32(-1), Builder.getInt32(0)});


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D108971.369642.patch
Type: text/x-patch
Size: 4188 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20210831/688d2f7b/attachment-0001.bin>