[PATCH] D21690: Fix size computation of array allocation in inline cost analysis

[Easwaran Raman via llvm-commits]

eraman created this revision.
eraman added a reviewer: chandlerc.
eraman added a subscriber: llvm-commits.

There are two bugs in computing size allocated by an array alloca:
* For primitive types, it computes the number of bits and there is a FIXME
* For aggregate types, the computed size is always 0.

The fix is to use DL.getTypeAllocSize(Ty) as it is done for static alloca

http://reviews.llvm.org/D21690

Files:
  lib/Analysis/InlineCost.cpp
  test/Transforms/Inline/array-alloca.ll

Index: test/Transforms/Inline/array-alloca.ll
===================================================================
--- /dev/null
+++ test/Transforms/Inline/array-alloca.ll
@@ -0,0 +1,26 @@
+; RUN: opt -inline -S < %s | FileCheck %s
+%struct.A = type { i32 }
+
+define void @callee1(i32 %M) {
+entry:
+  %vla = alloca i32, i32 %M, align 16
+  ret void
+}
+
+define void @callee2(i32 %M) {
+entry:
+  %vla = alloca %struct.A, i32 %M, align 16
+  ret void
+}
+
+; CHECK-LABEL: @caller
+define void @caller() #0 {
+entry:
+  call void @caller()
+; CHECK-NOT: call void @callee1
+  call void @callee1(i32 256)
+; CHECK: call void @callee2
+  call void @callee2(i32 4096)
+  ret void
+}
+
Index: lib/Analysis/InlineCost.cpp
===================================================================
--- lib/Analysis/InlineCost.cpp
+++ lib/Analysis/InlineCost.cpp
@@ -339,9 +339,9 @@
   if (I.isArrayAllocation()) {
     Constant *Size = SimplifiedValues.lookup(I.getArraySize());
     if (auto *AllocSize = dyn_cast_or_null<ConstantInt>(Size)) {
+      const DataLayout &DL = F.getParent()->getDataLayout();
       Type *Ty = I.getAllocatedType();
-      // FIXME: This can't be right. AllocatedSize is in *bytes*.
-      AllocatedSize += Ty->getPrimitiveSizeInBits() * AllocSize->getZExtValue();
+      AllocatedSize += DL.getTypeAllocSize(Ty) * AllocSize->getZExtValue();
       return Base::visitAlloca(I);
     }
   }


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