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Reapply r52397 (make IPConstProp promote returned arguments), but fixed this

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time. Sorry for the trouble!

This time, also add a testcase, which I should have done in the first place...

llvm-svn: 52455
This commit is contained in:
Matthijs Kooijman 2008-06-18 08:30:37 +00:00
parent 0570953e28
commit 8177832230
2 changed files with 64 additions and 3 deletions
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21
lib/Transforms/IPO/IPConstantPropagation.cpp
View File

@ -145,6 +145,10 @@ bool IPCP::PropagateConstantsIntoArguments(Function &F) {
// all callers that use those return values with the constant value. This will
// leave in the actual return values and instructions, but deadargelim will
// clean that up.
//
// Additionally if a function always returns one of its arguments directly,
// callers will be updated to use the value they pass in directly instead of
// using the return value.
bool IPCP::PropagateConstantReturn(Function &F) {
if (F.getReturnType() == Type::VoidTy)
return false; // No return value.
@ -188,8 +192,8 @@ bool IPCP::PropagateConstantReturn(Function &F) {
if (isa<UndefValue>(V))
continue;
// Try to see if all the rets return the same constant.
if (isa<Constant>(V)) {
// Try to see if all the rets return the same constant or argument.
if (isa<Constant>(V) || isa<Argument>(V)) {
if (isa<UndefValue>(RV)) {
// No value found yet? Try the current one.
RetVals[i] = V;
@ -227,7 +231,13 @@ bool IPCP::PropagateConstantReturn(Function &F) {
MadeChange = true;
if (STy == 0) {
Call->replaceAllUsesWith(RetVals[0]);
Value* New = RetVals[0];
if (Argument *A = dyn_cast<Argument>(New))
// Was an argument returned? Then find the corresponding argument in
// the call instruction and use that. Add 1 to the argument number
// to skip the first argument (the function itself).
New = Call->getOperand(A->getArgNo() + 1);
Call->replaceAllUsesWith(New);
continue;
}
@ -255,6 +265,11 @@ bool IPCP::PropagateConstantReturn(Function &F) {
if (index != -1) {
Value *New = RetVals[index];
if (New) {
if (Argument *A = dyn_cast<Argument>(New))
// Was an argument returned? Then find the corresponding argument in
// the call instruction and use that. Add 1 to the argument number
// to skip the first argument (the function itself).
New = Call->getOperand(A->getArgNo() + 1);
Ins->replaceAllUsesWith(New);
Ins->eraseFromParent();
}

46
test/Transforms/IPConstantProp/return-argument.ll Normal file
View File

@ -0,0 +1,46 @@
; RUN: llvm-as < %s | opt -ipconstprop | llvm-dis > %t
; RUN: cat %t | grep {store i32 %Z, i32\\* %Q}
; RUN: cat %t | grep {add i32 1, 3}
;; This function returns its second argument on all return statements
define internal i32* @incdec(i1 %C, i32* %V) {
%X = load i32* %V
br i1 %C, label %T, label %F
T: ; preds = %0
%X1 = add i32 %X, 1
store i32 %X1, i32* %V
ret i32* %V
F: ; preds = %0
%X2 = sub i32 %X, 1
store i32 %X2, i32* %V
ret i32* %V
}
;; This function returns its first argument as a part of a multiple return
;; value
define internal { i32, i32 } @foo(i32 %A, i32 %B) {
%X = add i32 %A, %B
%Y = insertvalue { i32, i32 } undef, i32 %A, 0
%Z = insertvalue { i32, i32 } %Y, i32 %X, 1
ret { i32, i32 } %Z
}
define void @caller(i1 %C) {
%Q = alloca i32
;; Call incdec to see if %W is properly replaced by %Q
%W = call i32* @incdec(i1 %C, i32* %Q ) ; <i32> [#uses=1]
;; Call @foo twice, to prevent the arguments from propagating into the
;; function (so we can check the returned argument is properly
;; propagated per-caller).
%S1 = call { i32, i32 } @foo(i32 1, i32 2);
%X1 = extractvalue { i32, i32 } %S1, 0
%S2 = call { i32, i32 } @foo(i32 3, i32 4);
%X2 = extractvalue { i32, i32 } %S2, 0
;; Do some stuff with the returned values which we can grep for
%Z = add i32 %X1, %X2
store i32 %Z, i32* %W
ret void
}