Make instcombine ensure that all allocas are explicitly aligned at at
least their preferred alignment.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@62176 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp
index ee3596b..f640915 100644
--- a/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -10775,12 +10775,17 @@
}
}
- // If alloca'ing a zero byte object, replace the alloca with a null pointer.
- // Note that we only do this for alloca's, because malloc should allocate and
- // return a unique pointer, even for a zero byte allocation.
- if (isa<AllocaInst>(AI) && AI.getAllocatedType()->isSized() &&
- TD->getTypePaddedSize(AI.getAllocatedType()) == 0)
- return ReplaceInstUsesWith(AI, Constant::getNullValue(AI.getType()));
+ if (isa<AllocaInst>(AI) && AI.getAllocatedType()->isSized()) {
+ // If alloca'ing a zero byte object, replace the alloca with a null pointer.
+ // Note that we only do this for alloca's, because malloc should allocate and
+ // return a unique pointer, even for a zero byte allocation.
+ if (TD->getTypePaddedSize(AI.getAllocatedType()) == 0)
+ return ReplaceInstUsesWith(AI, Constant::getNullValue(AI.getType()));
+
+ // If the alignment is 0 (unspecified), assign it the preferred alignment.
+ if (AI.getAlignment() == 0)
+ AI.setAlignment(TD->getPrefTypeAlignment(AI.getAllocatedType()));
+ }
return 0;
}