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Fix a pretty serious misfeature of the inliner: if it inlines a function

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with multiple return values it inserts a PHI to merge them all together.
However, if the return values are all the same, it ends up with a pointless
PHI and this pointless PHI happens to really block SRoA from happening in 
at least a silly C++ example written by Doug, but probably others.  This 
fixes rdar://7339069.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@85206 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2009-10-27 05:39:41 +00:00
parent 744f19aa15
commit c581acbbba
2 changed files with 41 additions and 1 deletions
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9
lib/Transforms/Utils/InlineFunction.cpp
View File

@ -619,8 +619,17 @@ bool llvm::InlineFunction(CallSite CS, CallGraph *CG, const TargetData *TD,
"Ret value not consistent in function!"); "Ret value not consistent in function!");
PHI->addIncoming(RI->getReturnValue(), RI->getParent()); PHI->addIncoming(RI->getReturnValue(), RI->getParent());
} }
// Now that we inserted the PHI, check to see if it has a single value
// (e.g. all the entries are the same or undef). If so, remove the PHI so
// it doesn't block other optimizations.
if (Value *V = PHI->hasConstantValue()) {
PHI->replaceAllUsesWith(V);
PHI->eraseFromParent();
}
} }
// Add a branch to the merge points and remove return instructions. // Add a branch to the merge points and remove return instructions.
for (unsigned i = 0, e = Returns.size(); i != e; ++i) { for (unsigned i = 0, e = Returns.size(); i != e; ++i) {
ReturnInst *RI = Returns[i]; ReturnInst *RI = Returns[i];

33
test/Transforms/Inline/basictest.ll
View File

@ -1,4 +1,4 @@
; RUN: opt < %s -inline -S | FileCheck %s ; RUN: opt < %s -inline -scalarrepl -S | FileCheck %s
define i32 @test1f(i32 %i) { define i32 @test1f(i32 %i) {
ret i32 %i ret i32 %i
@ -13,3 +13,34 @@ define i32 @test1(i32 %W) {
; CHECK-NEXT: ret i32 %Y ; CHECK-NEXT: ret i32 %Y
} }
; rdar://7339069
%T = type { i32, i32 }
; CHECK-NOT: @test2f
define internal %T* @test2f(i1 %cond, %T* %P) {
br i1 %cond, label %T, label %F
T:
%A = getelementptr %T* %P, i32 0, i32 0
store i32 42, i32* %A
ret %T* %P
F:
ret %T* %P
}
define i32 @test2(i1 %cond) {
%A = alloca %T
%B = call %T* @test2f(i1 %cond, %T* %A)
%C = getelementptr %T* %B, i32 0, i32 0
%D = load i32* %C
ret i32 %D
; CHECK: @test2(
; CHECK-NOT: = alloca
; CHECK: ret i32 42
}