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Avoid inserting noop's in the middle of a loop.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60141 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Evan Cheng 2008-11-27 01:16:00 +00:00
parent 884c70c912
commit df90841690
2 changed files with 39 additions and 1 deletions
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8
lib/CodeGen/LoopAligner.cpp
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@ -64,8 +64,14 @@ bool LoopAligner::runOnMachineFunction(MachineFunction &MF) {
for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I) {
MachineBasicBlock *MBB = I;
if (MLI->isLoopHeader(MBB))
if (MLI->isLoopHeader(MBB)) {
MachineBasicBlock *PredBB = prior(I);
if (MLI->getLoopFor(MBB) == MLI->getLoopFor(PredBB))
// If previously BB is in the same loop, don't align this BB. We want
// to prevent adding noop's inside a loop.
continue;
MBB->setAlignment(Align);
}
}
return true;

32
test/CodeGen/X86/avoid-loop-align.ll Normal file
View File

@ -0,0 +1,32 @@
; RUN: llvm-as < %s | llc -mtriple=i386-apple-darwin | grep align | count 1
@A = common global [100 x i32] zeroinitializer, align 32 ; <[100 x i32]*> [#uses=1]
define i8* @test(i8* %Q, i32* %L) nounwind {
entry:
%tmp = tail call i32 (...)* @foo() nounwind ; <i32> [#uses=2]
%tmp1 = inttoptr i32 %tmp to i8* ; <i8*> [#uses=1]
br label %bb1
bb: ; preds = %bb1, %bb1
%indvar.next = add i32 %P.0.rec, 1 ; <i32> [#uses=1]
br label %bb1
bb1: ; preds = %bb, %entry
%P.0.rec = phi i32 [ 0, %entry ], [ %indvar.next, %bb ] ; <i32> [#uses=2]
%P.0 = getelementptr i8* %tmp1, i32 %P.0.rec ; <i8*> [#uses=3]
%tmp2 = load i8* %P.0, align 1 ; <i8> [#uses=1]
switch i8 %tmp2, label %bb4 [
i8 12, label %bb
i8 42, label %bb
]
bb4: ; preds = %bb1
%tmp3 = ptrtoint i8* %P.0 to i32 ; <i32> [#uses=1]
%tmp4 = sub i32 %tmp3, %tmp ; <i32> [#uses=1]
%tmp5 = getelementptr [100 x i32]* @A, i32 0, i32 %tmp4 ; <i32*> [#uses=1]
store i32 4, i32* %tmp5, align 4
ret i8* %P.0
}
declare i32 @foo(...)