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Situations can arise when you have a function called that returns a 'void', but

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is bitcast to return a floating point value. The result of the instruction may
not be used by the program afterwards, and LLVM will happily remove all
instructions except the call. But, on some platforms, if a value is returned as
a floating point, it may need to be removed from the stack (like x87). Thus, we
can't get rid of the bitcast even if there isn't a use of the value.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@51134 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Bill Wendling 2008-05-14 22:45:20 +00:00
parent 6a33cc12eb
commit a6c3112b1f
3 changed files with 30 additions and 4 deletions
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4
lib/Transforms/Scalar/InstructionCombining.cpp
View File

@ -8940,7 +8940,7 @@ bool InstCombiner::transformConstExprCastCall(CallSite CS) {
// Check to see if we are changing the return type...
if (OldRetTy != FT->getReturnType()) {
if (Callee->isDeclaration() && !Caller->use_empty() &&
if (Callee->isDeclaration() &&
// Conversion is ok if changing from pointer to int of same size.
!(isa<PointerType>(FT->getReturnType()) &&
TD->getIntPtrType() == OldRetTy))
@ -11516,7 +11516,7 @@ bool InstCombiner::runOnFunction(Function &F) {
// Iterate while there is work to do.
unsigned Iteration = 0;
while (DoOneIteration(F, Iteration++))
while (DoOneIteration(F, Iteration++))
EverMadeChange = true;
return EverMadeChange;
}

3
test/Transforms/InstCombine/2003-11-13-ConstExprCastCall.ll
View File

@ -3,7 +3,6 @@
declare void @free(i8*)
define void @test(i32* %X) {
call i32 (...)* bitcast (void (i8*)* @free to i32 (...)*)( i32* %X ) ; <i32>:1 [#uses=0]
call void (...)* bitcast (void (i8*)* @free to void (...)*)( i32* %X ) ; <i32>:1 [#uses=0]
ret void
}

27
test/Transforms/InstCombine/fp-ret-bitcast.ll Normal file
View File

@ -0,0 +1,27 @@
; RUN: llvm-as < %s | opt -instcombine | llvm-dis | \
; RUN: grep {call float bitcast} | count 1
%struct.NSObject = type { %struct.objc_class* }
%struct.NSArray = type { %struct.NSObject }
%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"
@"\01L_OBJC_SELECTOR_REFERENCES_81" = internal global %struct.objc_selector* bitcast ([15 x i8]* @"\01L_OBJC_METH_VAR_NAME_112" to %struct.objc_selector*), section "__OBJC,__message_refs,literal_pointers,no_dead_strip"
define void @bork() nounwind {
entry:
%color = alloca %struct.NSArray*
%color.466 = alloca %struct.NSObject*
%tmp103 = load %struct.NSArray** %color, align 4
%tmp103104 = getelementptr %struct.NSArray* %tmp103, i32 0, i32 0
store %struct.NSObject* %tmp103104, %struct.NSObject** %color.466, align 4
%tmp105 = load %struct.objc_selector** @"\01L_OBJC_SELECTOR_REFERENCES_81", align 4
%tmp106 = load %struct.NSObject** %color.466, align 4
%tmp107 = call float bitcast (void (%struct.NSObject*, ...)* @objc_msgSend_fpret to float (%struct.NSObject*, %struct.objc_selector*)*)( %struct.NSObject* %tmp106, %struct.objc_selector* %tmp105 ) nounwind
br label %exit
exit:
ret void
}
declare void @objc_msgSend_fpret(%struct.NSObject*, ...)