[PATCH] D48330: [GVN] Avoid casting a vector of size less than 8 bits to i8

[Matthew Voss via Phabricator via llvm-commits]

ormris updated this revision to Diff 152376.
ormris added a comment.

Merge two tests. Add comment.


Repository:
  rL LLVM

https://reviews.llvm.org/D48330

Files:
  lib/Transforms/Utils/VNCoercion.cpp
  test/Transforms/GVN/pr28879.ll


Index: test/Transforms/GVN/pr28879.ll
===================================================================
--- /dev/null
+++ test/Transforms/GVN/pr28879.ll
@@ -0,0 +1,34 @@
+; RUN: opt -gvn <%s -S -o - | FileCheck %s
+
+define void @f() {
+entry:
+  %a = alloca <7 x i1>, align 2
+  store <7 x i1> undef, <7 x i1>* %a, align 2
+; CHECK: store <7 x i1> undef, <7 x i1>*
+  %0 = getelementptr inbounds <7 x i1>, <7 x i1>* %a, i64 0, i64 0
+  %val = load i1, i1* %0, align 2
+; CHECK: load i1, i1* 
+  br i1 %val, label %cond.true, label %cond.false
+
+cond.true:
+  ret void
+
+cond.false:
+  ret void
+}
+
+define <7 x i1> @g(<7 x i1>* %a) {
+entry:
+  %vec = load <7 x i1>, <7 x i1>* %a
+; CHECK: load <7 x i1>, <7 x i1>*
+  %0 = getelementptr inbounds <7 x i1>, <7 x i1>* %a, i64 0, i64 0
+  %val = load i1, i1* %0, align 2
+; CHECK: load i1, i1*
+  br i1 %val, label %cond.true, label %cond.false
+
+cond.true:
+  ret <7 x i1> %vec
+
+cond.false:
+  ret <7 x i1> <i1 false, i1 false, i1 false, i1 false, i1 false, i1 false, i1 false>
+}
Index: lib/Transforms/Utils/VNCoercion.cpp
===================================================================
--- lib/Transforms/Utils/VNCoercion.cpp
+++ lib/Transforms/Utils/VNCoercion.cpp
@@ -20,8 +20,14 @@
       StoredVal->getType()->isStructTy() || StoredVal->getType()->isArrayTy())
     return false;
 
+  uint64_t StoreSize = DL.getTypeSizeInBits(StoredVal->getType());
+
+  // The store size must be byte-aligned to support future type casts.
+  if (llvm::alignTo(StoreSize, 8) != StoreSize)
+    return false;
+
   // The store has to be at least as big as the load.
-  if (DL.getTypeSizeInBits(StoredVal->getType()) < DL.getTypeSizeInBits(LoadTy))
+  if (StoreSize < DL.getTypeSizeInBits(LoadTy))
     return false;
 
   // Don't coerce non-integral pointers to integers or vice versa.


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