[PATCH] D19563: AMDGPU: Fix mishandling array allocations when promoting alloca

[Matt Arsenault via llvm-commits]

arsenm created this revision.
arsenm added a reviewer: tstellarAMD.
arsenm added a subscriber: llvm-commits.
Herald added a subscriber: arsenm.

The canonical form for allocas is a single allocation of the array type.
In case we see a non-canonical array alloca, make sure we aren't
replacing this with an array N times smaller.

http://reviews.llvm.org/D19563

Files:
  lib/Target/AMDGPU/AMDGPUPromoteAlloca.cpp
  test/CodeGen/AMDGPU/promote-alloca-array-allocation.ll

Index: test/CodeGen/AMDGPU/promote-alloca-array-allocation.ll
===================================================================
--- /dev/null
+++ test/CodeGen/AMDGPU/promote-alloca-array-allocation.ll
@@ -0,0 +1,50 @@
+; RUN: opt -S -mtriple=amdgcn-amd-amdhsa -amdgpu-promote-alloca < %s | FileCheck %s
+
+; Make sure this allocates the correct size if the alloca has a non-0
+; number of elements.
+
+; CHECK-LABEL: @array_alloca(
+; CHECK: %stack = alloca i32, i32 5, align 4
+define void @array_alloca(i32 addrspace(1)* nocapture %out, i32 addrspace(1)* nocapture %in) #0 {
+entry:
+  %stack = alloca i32, i32 5, align 4
+  %ld0 = load i32, i32 addrspace(1)* %in, align 4
+  %arrayidx1 = getelementptr inbounds i32, i32* %stack, i32 %ld0
+  store i32 4, i32* %arrayidx1, align 4
+  %arrayidx2 = getelementptr inbounds i32, i32 addrspace(1)* %in, i32 1
+  %ld1 = load i32, i32 addrspace(1)* %arrayidx2, align 4
+  %arrayidx3 = getelementptr inbounds i32, i32* %stack, i32 %ld1
+  store i32 5, i32* %arrayidx3, align 4
+  %arrayidx10 = getelementptr inbounds i32, i32* %stack, i32 0
+  %ld2 = load i32, i32* %arrayidx10, align 4
+  store i32 %ld2, i32 addrspace(1)* %out, align 4
+  %arrayidx12 = getelementptr inbounds i32, i32* %stack, i32 1
+  %ld3 = load i32, i32* %arrayidx12
+  %arrayidx13 = getelementptr inbounds i32, i32 addrspace(1)* %out, i32 1
+  store i32 %ld3, i32 addrspace(1)* %arrayidx13
+  ret void
+}
+
+; CHECK-LABEL: @array_alloca_dynamic(
+; CHECK: %stack = alloca i32, i32 %size, align 4
+define void @array_alloca_dynamic(i32 addrspace(1)* nocapture %out, i32 addrspace(1)* nocapture %in, i32 %size) #0 {
+entry:
+  %stack = alloca i32, i32 %size, align 4
+  %ld0 = load i32, i32 addrspace(1)* %in, align 4
+  %arrayidx1 = getelementptr inbounds i32, i32* %stack, i32 %ld0
+  store i32 4, i32* %arrayidx1, align 4
+  %arrayidx2 = getelementptr inbounds i32, i32 addrspace(1)* %in, i32 1
+  %ld1 = load i32, i32 addrspace(1)* %arrayidx2, align 4
+  %arrayidx3 = getelementptr inbounds i32, i32* %stack, i32 %ld1
+  store i32 5, i32* %arrayidx3, align 4
+  %arrayidx10 = getelementptr inbounds i32, i32* %stack, i32 0
+  %ld2 = load i32, i32* %arrayidx10, align 4
+  store i32 %ld2, i32 addrspace(1)* %out, align 4
+  %arrayidx12 = getelementptr inbounds i32, i32* %stack, i32 1
+  %ld3 = load i32, i32* %arrayidx12
+  %arrayidx13 = getelementptr inbounds i32, i32 addrspace(1)* %out, i32 1
+  store i32 %ld3, i32 addrspace(1)* %arrayidx13
+  ret void
+}
+
+attributes #0 = { nounwind }
Index: lib/Target/AMDGPU/AMDGPUPromoteAlloca.cpp
===================================================================
--- lib/Target/AMDGPU/AMDGPUPromoteAlloca.cpp
+++ lib/Target/AMDGPU/AMDGPUPromoteAlloca.cpp
@@ -481,7 +481,9 @@
 }
 
 void AMDGPUPromoteAlloca::handleAlloca(AllocaInst &I) {
-  if (!I.isStaticAlloca())
+  // Array allocations are probably not worth handling, since an allocation of
+  // the array type is the canonical form.
+  if (!I.isStaticAlloca() || I.isArrayAllocation())
     return;
 
   IRBuilder<> Builder(&I);


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