"Allow LICM to sink or lift loads from constant memory. Also add a test
case for this.
This allows instructions like loads from global variables declared to
be constant to be moved out of loops."
Patch by Stefanus Du Toit!
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@53945 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Scalar/LICM.cpp b/lib/Transforms/Scalar/LICM.cpp
index f7afaf4..13440c1 100644
--- a/lib/Transforms/Scalar/LICM.cpp
+++ b/lib/Transforms/Scalar/LICM.cpp
@@ -370,6 +370,11 @@
if (LI->isVolatile())
return false; // Don't hoist volatile loads!
+ // Loads from constant memory are always safe to move, even if they end up
+ // in the same alias set as something that ends up being modified.
+ if (AA->pointsToConstantMemory(LI->getOperand(0)))
+ return true;
+
// Don't hoist loads which have may-aliased stores in loop.
unsigned Size = 0;
if (LI->getType()->isSized())