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[SimplifyCFG] Tail-merge calls with sideeffects 

This was deliberately disabled during my rewrite of SinkIfThenToEnd to keep behaviour
at least vaguely consistent with the previous version and keep it as close to NFC as
I could.

There's no real reason not to merge sideeffect calls though, so let's do it! Small fixup
along the way to ensure we don't create indirect calls.

Should fix PR28964.

llvm-svn: 280215
This commit is contained in:
James Molloy 2016-08-31 10:46:16 +00:00
parent 7b09af193a
commit 923e98c232
2 changed files with 27 additions and 8 deletions
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10
llvm/lib/Transforms/Utils/SimplifyCFG.cpp
View File

@ -1433,11 +1433,6 @@ static bool canSinkLastInstruction(ArrayRef<BasicBlock*> Blocks,
if (isa<PHINode>(I) || I->isEHPad() || isa<AllocaInst>(I) ||
I->getType()->isTokenTy())
return false;
// Apart from loads and stores, we won't move anything that could
// change memory or have sideeffects.
if (!isa<StoreInst>(I) && !isa<LoadInst>(I) &&
(I->mayHaveSideEffects() || I->mayHaveSideEffects()))
return false;
// Everything must have only one use too, apart from stores which
// have no uses.
if (!isa<StoreInst>(I) && !I->hasOneUse())
@ -1472,10 +1467,11 @@ static bool canSinkLastInstruction(ArrayRef<BasicBlock*> Blocks,
if (!canReplaceOperandWithVariable(I0, OI))
// We can't create a PHI from this GEP.
return false;
if ((isa<CallInst>(I0) || isa<InvokeInst>(I0)) && OI != 0)
// Don't create indirect calls!
// Don't create indirect calls! The called value is the final operand.
if ((isa<CallInst>(I0) || isa<InvokeInst>(I0)) && OI == OE - 1) {
// FIXME: if the call was *already* indirect, we should do this.
return false;
}
++NumPHIsRequired;
}
}

25
llvm/test/Transforms/SimplifyCFG/sink-common-code.ll
View File

@ -344,6 +344,29 @@ if.end:
; CHECK-NOT: load
; CHECK-NOT: store
; The call should be commoned.
define i32 @test13a(i1 zeroext %flag, i32 %w, i32 %x, i32 %y) {
entry:
br i1 %flag, label %if.then, label %if.else
if.then:
%sv1 = call i32 @bar(i32 %x)
br label %if.end
if.else:
%sv2 = call i32 @bar(i32 %y)
br label %if.end
if.end:
%p = phi i32 [ %sv1, %if.then ], [ %sv2, %if.else ]
ret i32 1
}
declare i32 @bar(i32)
; CHECK-LABEL: test13a
; CHECK: %[[x:.*]] = select i1 %flag
; CHECK: call i32 @bar(i32 %[[x]])
; CHECK: !0 = !{!1, !1, i64 0}
; CHECK: !1 = !{!"float", !2}
; CHECK: !2 = !{!"an example type tree"}
; CHECK: !2 = !{!"an example type tree"}