In this recipe, we will briefly discuss a transformation pass that deals with memory optimization.
Write the test code on which we will run the
memcpy
optimization pass:$ cat memcopytest.ll @cst = internal constant [3 x i32] [i32 -1, i32 -1, i32 -1], align 4 declare void @llvm.memcpy.p0i8.p0i8.i64(i8* nocapture, i8* nocapture, i64, i32, i1) nounwind declare void @foo(i32*) nounwind define void @test1() nounwind { %arr = alloca [3 x i32], align 4 %arr_i8 = bitcast [3 x i32]* %arr to i8* call void @llvm.memcpy.p0i8.p0i8.i64(i8* %arr_i8, i8* bitcast ([3 x i32]* @cst to i8*), i64 12, i32 4, i1 false) %arraydecay = getelementptr inbounds [3 x i32], [3 x i32]* %arr, i64 0, i64 0 call void @foo(i32* %arraydecay) nounwind ret void }
Run the
memcpyopt
pass on the preceding test case:$ opt -memcpyopt -S memcopytest.ll ; ModuleID = ' memcopytest.ll' @cst = internal...