Implement PR2370: memmove(x,x,size) -> noop.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@51636 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp
index 2020415..8c2dc3e 100644
--- a/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -9131,6 +9131,10 @@
CI.setOperand(0, Intrinsic::getDeclaration(M, MemCpyID));
Changed = true;
}
+
+ // memmove(x,x,size) -> noop.
+ if (MMI->getSource() == MMI->getDest())
+ return EraseInstFromFunction(CI);
}
// If we can determine a pointer alignment that is bigger than currently
diff --git a/test/Transforms/InstCombine/memmove.ll b/test/Transforms/InstCombine/memmove.ll
index 2cb346f..09ec67d 100644
--- a/test/Transforms/InstCombine/memmove.ll
+++ b/test/Transforms/InstCombine/memmove.ll
@@ -34,3 +34,9 @@
ret i32 0
}
+; PR2370
+define void @test4(i8* %a) {
+ tail call void @llvm.memmove.i32( i8* %a, i8* %a, i32 100, i32 1 )
+ ret void
+}
+