Teach argpromote to ruthlessly hack small byval structs when it can

get away with it, which exposes opportunities to eliminate the memory
objects entirely.  For example, we now compile byval.ll to:

define internal void @f1(i32 %b.0, i64 %b.1) {
entry:
	%tmp2 = add i32 %b.0, 1		; <i32> [#uses=0]
	ret void
}

define i32 @main() nounwind  {
entry:
	call void @f1( i32 1, i64 2 )
	ret i32 0
}

This seems like it would trigger a lot for code that passes around small
structs (e.g. SDOperand's or _Complex)...



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@45886 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 24 insertions, 0 deletions

diff --git a/test/Transforms/ArgumentPromotion/byval.ll b/test/Transforms/ArgumentPromotion/byval.ll
new file mode 100644
index 0000000..3a3458f
--- /dev/null
+++ b/test/Transforms/ArgumentPromotion/byval.ll
@@ -0,0 +1,24 @@
+; RUN: llvm-as < %s | opt -argpromotion -scalarrepl | llvm-dis | not grep load
+; Argpromote + scalarrepl should change this to passing the two integers by value.
+
+	%struct.ss = type { i32, i64 }
+
+define internal void @f(%struct.ss* byval  %b) nounwind  {
+entry:
+	%tmp = getelementptr %struct.ss* %b, i32 0, i32 0		; <i32*> [#uses=2]
+	%tmp1 = load i32* %tmp, align 4		; <i32> [#uses=1]
+	%tmp2 = add i32 %tmp1, 1		; <i32> [#uses=1]
+	store i32 %tmp2, i32* %tmp, align 4
+	ret void
+}
+
+define i32 @main() nounwind  {
+entry:
+	%S = alloca %struct.ss		; <%struct.ss*> [#uses=4]
+	%tmp1 = getelementptr %struct.ss* %S, i32 0, i32 0		; <i32*> [#uses=1]
+	store i32 1, i32* %tmp1, align 8
+	%tmp4 = getelementptr %struct.ss* %S, i32 0, i32 1		; <i64*> [#uses=1]
+	store i64 2, i64* %tmp4, align 4
+	call void @f( %struct.ss* byval  %S ) nounwind 
+	ret i32 0
+}