[llvm-commits] [llvm] r51134 - in /llvm/trunk: lib/Transforms/Scalar/InstructionCombining.cpp test/Transforms/InstCombine/2003-11-13-ConstExprCastCall.ll test/Transforms/InstCombine/fp-ret-bitcast.ll

[Duncan Sands]

Hi Chris,

> I'm saying that the optimization is important, and was implemented for  
> a reason :).  The issue is code like this:
> 
> --- a.c
> int foo()
> int bar() {
>    return foo(1, 2, 3);
> }
> --- b.c
> void foo(int x, int y, int z) { return x+y+z; }
> 
> 
> 
> After llvm-link runs, you get the bitcast of function.  It is  
> important to have instcombine squash this so that (e.g.) inline can  
> see a direct call.  However, it should only do this in cases that  
> don't violate the ABI :)

in your example you can see the function definition (and not just
a declaration), so doing the transform only when you have the
declaration of the callee to hand would be ok for this example.

Ciao,

Duncan.

PS: I just chucked some code into GlobalOpt that teaches it to change
the type of a declaration if the only use is a bitcast to a function
type.  It seems to work!  This transforms the objc testcase to:

; ModuleID = 'out.bc'
	%struct.NSArray = type { %struct.NSObject }
	%struct.NSObject = type { %struct.objc_class* }
	%struct.objc_class = type opaque
	%struct.objc_selector = type opaque
@"\01L_OBJC_METH_VAR_NAME_112" = internal global [15 x i8] c"whiteComponent\00", section "__TEXT,__cstring,cstring_literals"		; <[15 x i8]*> [#uses=1]

define void @bork() nounwind  {
entry:
	%color = alloca %struct.NSArray*		; <%struct.NSArray**> [#uses=1]
	%color.466 = alloca %struct.NSObject*		; <%struct.NSObject**> [#uses=2]
	%tmp103 = load %struct.NSArray** %color, align 4		; <%struct.NSArray*> [#uses=1]
	%tmp103104 = getelementptr %struct.NSArray* %tmp103, i32 0, i32 0		; <%struct.NSObject*> [#uses=1]
	store %struct.NSObject* %tmp103104, %struct.NSObject** %color.466, align 4
	%tmp106 = load %struct.NSObject** %color.466, align 4		; <%struct.NSObject*> [#uses=2]
	%tmp107 = call float @objc_msgSend_fpret( %struct.NSObject* %tmp106, %struct.objc_selector* bitcast ([15 x i8]* @"\01L_OBJC_METH_VAR_NAME_112" to %struct.objc_selector*) ) nounwind 		; <float> [#uses=0]
	%tmp108 = call float @objc_msgSend_fpret( %struct.NSObject* %tmp106, %struct.objc_selector* bitcast ([15 x i8]* @"\01L_OBJC_METH_VAR_NAME_112" to %struct.objc_selector*) ) nounwind 		; <float> [#uses=0]
	br label %exit

exit:		; preds = %entry
	ret void
}

declare float @objc_msgSend_fpret(%struct.NSObject*, %struct.objc_selector*)