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[ShrinkWrap] Refactor the handling of infinite loop in the analysis. 

- Strenghten the logic to be sure we hoist the restore point out of the current
  loop. (The fixes a bug with infinite loop, added as part of the patch.)
- Walk over the exit blocks of the current loop to conver to the desired restore
  point in one iteration of the update loop.

llvm-svn: 247958
This commit is contained in:
Quentin Colombet 2015-09-17 23:21:34 +00:00
parent 0b6003f3e6
commit b4c6886215
5 changed files with 229 additions and 9 deletions
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20
llvm/lib/CodeGen/ShrinkWrap.cpp
View File

@ -313,16 +313,18 @@ void ShrinkWrap::updateSaveRestorePoints(MachineBasicBlock &MBB) {
// for a post-dominator outside the loop.
SmallVector<MachineBasicBlock*, 4> ExitBlocks;
MLI->getLoopFor(Restore)->getExitingBlocks(ExitBlocks);
if (ExitBlocks.empty()) {
Restore = nullptr;
break;
// Push Restore outside of this loop.
// Look for the immediate post-dominator of the loop exits.
MachineBasicBlock *IPdom = Restore;
for (MachineBasicBlock *LoopExitBB: ExitBlocks) {
IPdom = FindIDom<>(*IPdom, LoopExitBB->successors(), *MPDT);
if (!IPdom)
break;
}
// Push Restore outside of this loop if immediate post-dominator is
// different from restore block. If immediate post-dominator is not
// different, bail out.
MachineBasicBlock *IPdom =
FindIDom<>(*Restore, Restore->successors(), *MPDT);
if (IPdom != Restore)
// If the immediate post-dominator is not in a less nested loop,
// then we are stuck in a program with an infinite loop.
// In that case, we will not find a safe point, hence, bail out.
if (IPdom && MLI->getLoopDepth(IPdom) < MLI->getLoopDepth(Restore))
Restore = IPdom;
else {
Restore = nullptr;

62
llvm/test/CodeGen/AArch64/arm64-shrink-wrapping.ll
View File

@ -568,3 +568,65 @@ for.body: ; preds = %for.body, %entry
if.end:
ret void
}
; Another infinite loop test this time with a body bigger than just one block.
; CHECK-LABEL: infiniteloop2
; CHECK: ret
define void @infiniteloop2() {
entry:
br i1 undef, label %if.then, label %if.end
if.then:
%ptr = alloca i32, i32 4
br label %for.body
for.body: ; preds = %for.body, %entry
%sum.03 = phi i32 [ 0, %if.then ], [ %add, %body1 ], [ 1, %body2]
%call = tail call i32 asm "mov $0, #0", "=r,~{x19}"()
%add = add nsw i32 %call, %sum.03
store i32 %add, i32* %ptr
br i1 undef, label %body1, label %body2
body1:
tail call void asm sideeffect "nop", "~{x19}"()
br label %for.body
body2:
tail call void asm sideeffect "nop", "~{x19}"()
br label %for.body
if.end:
ret void
}
; Another infinite loop test this time with two nested infinite loop.
; CHECK-LABEL: infiniteloop3
; CHECK: ret
define void @infiniteloop3() {
entry:
br i1 undef, label %loop2a, label %body
body: ; preds = %entry
br i1 undef, label %loop2a, label %end
loop1: ; preds = %loop2a, %loop2b
%var.phi = phi i32* [ %next.phi, %loop2b ], [ %var, %loop2a ]
%next.phi = phi i32* [ %next.load, %loop2b ], [ %next.var, %loop2a ]
%0 = icmp eq i32* %var, null
%next.load = load i32*, i32** undef
br i1 %0, label %loop2a, label %loop2b
loop2a: ; preds = %loop1, %body, %entry
%var = phi i32* [ null, %body ], [ null, %entry ], [ %next.phi, %loop1 ]
%next.var = phi i32* [ undef, %body ], [ null, %entry ], [ %next.load, %loop1 ]
br label %loop1
loop2b: ; preds = %loop1
%gep1 = bitcast i32* %var.phi to i32*
%next.ptr = bitcast i32* %gep1 to i32**
store i32* %next.phi, i32** %next.ptr
br label %loop1
end:
ret void
}

62
llvm/test/CodeGen/ARM/arm-shrink-wrapping.ll
View File

@ -562,3 +562,65 @@ for.body: ; preds = %for.body, %entry
if.end:
ret void
}
; Another infinite loop test this time with a body bigger than just one block.
; CHECK-LABEL: infiniteloop2
; CHECK: pop
define void @infiniteloop2() {
entry:
br i1 undef, label %if.then, label %if.end
if.then:
%ptr = alloca i32, i32 4
br label %for.body
for.body: ; preds = %for.body, %entry
%sum.03 = phi i32 [ 0, %if.then ], [ %add, %body1 ], [ 1, %body2]
%call = tail call i32 asm "mov $0, #0", "=r,~{r4}"()
%add = add nsw i32 %call, %sum.03
store i32 %add, i32* %ptr
br i1 undef, label %body1, label %body2
body1:
tail call void asm sideeffect "nop", "~{r4}"()
br label %for.body
body2:
tail call void asm sideeffect "nop", "~{r4}"()
br label %for.body
if.end:
ret void
}
; Another infinite loop test this time with two nested infinite loop.
; CHECK-LABEL: infiniteloop3
; CHECK: bx lr
define void @infiniteloop3() {
entry:
br i1 undef, label %loop2a, label %body
body: ; preds = %entry
br i1 undef, label %loop2a, label %end
loop1: ; preds = %loop2a, %loop2b
%var.phi = phi i32* [ %next.phi, %loop2b ], [ %var, %loop2a ]
%next.phi = phi i32* [ %next.load, %loop2b ], [ %next.var, %loop2a ]
%0 = icmp eq i32* %var, null
%next.load = load i32*, i32** undef
br i1 %0, label %loop2a, label %loop2b
loop2a: ; preds = %loop1, %body, %entry
%var = phi i32* [ null, %body ], [ null, %entry ], [ %next.phi, %loop1 ]
%next.var = phi i32* [ undef, %body ], [ null, %entry ], [ %next.load, %loop1 ]
br label %loop1
loop2b: ; preds = %loop1
%gep1 = bitcast i32* %var.phi to i32*
%next.ptr = bitcast i32* %gep1 to i32**
store i32* %next.phi, i32** %next.ptr
br label %loop1
end:
ret void
}

62
llvm/test/CodeGen/PowerPC/ppc-shrink-wrapping.ll
View File

@ -554,3 +554,65 @@ for.body: ; preds = %for.body, %entry
if.end:
ret void
}
; Another infinite loop test this time with a body bigger than just one block.
; CHECK-LABEL: infiniteloop2
; CHECK: blr
define void @infiniteloop2() {
entry:
br i1 undef, label %if.then, label %if.end
if.then:
%ptr = alloca i32, i32 4
br label %for.body
for.body: ; preds = %for.body, %entry
%sum.03 = phi i32 [ 0, %if.then ], [ %add, %body1 ], [ 1, %body2]
%call = tail call i32 asm "mftb $0, 268", "=r,~{r14}"()
%add = add nsw i32 %call, %sum.03
store i32 %add, i32* %ptr
br i1 undef, label %body1, label %body2
body1:
tail call void asm sideeffect "nop", "~{r14}"()
br label %for.body
body2:
tail call void asm sideeffect "nop", "~{r14}"()
br label %for.body
if.end:
ret void
}
; Another infinite loop test this time with two nested infinite loop.
; CHECK-LABEL: infiniteloop3
; CHECK: # %end
define void @infiniteloop3() {
entry:
br i1 undef, label %loop2a, label %body
body: ; preds = %entry
br i1 undef, label %loop2a, label %end
loop1: ; preds = %loop2a, %loop2b
%var.phi = phi i32* [ %next.phi, %loop2b ], [ %var, %loop2a ]
%next.phi = phi i32* [ %next.load, %loop2b ], [ %next.var, %loop2a ]
%0 = icmp eq i32* %var, null
%next.load = load i32*, i32** undef
br i1 %0, label %loop2a, label %loop2b
loop2a: ; preds = %loop1, %body, %entry
%var = phi i32* [ null, %body ], [ null, %entry ], [ %next.phi, %loop1 ]
%next.var = phi i32* [ undef, %body ], [ null, %entry ], [ %next.load, %loop1 ]
br label %loop1
loop2b: ; preds = %loop1
%gep1 = bitcast i32* %var.phi to i32*
%next.ptr = bitcast i32* %gep1 to i32**
store i32* %next.phi, i32** %next.ptr
br label %loop1
end:
ret void
}

32
llvm/test/CodeGen/X86/x86-shrink-wrapping.ll
View File

@ -697,3 +697,35 @@ body2:
if.end:
ret void
}
; Another infinite loop test this time with two nested infinite loop.
; CHECK-LABEL: infiniteloop3
; CHECK: retq
define void @infiniteloop3() {
entry:
br i1 undef, label %loop2a, label %body
body: ; preds = %entry
br i1 undef, label %loop2a, label %end
loop1: ; preds = %loop2a, %loop2b
%var.phi = phi i32* [ %next.phi, %loop2b ], [ %var, %loop2a ]
%next.phi = phi i32* [ %next.load, %loop2b ], [ %next.var, %loop2a ]
%0 = icmp eq i32* %var, null
%next.load = load i32*, i32** undef
br i1 %0, label %loop2a, label %loop2b
loop2a: ; preds = %loop1, %body, %entry
%var = phi i32* [ null, %body ], [ null, %entry ], [ %next.phi, %loop1 ]
%next.var = phi i32* [ undef, %body ], [ null, %entry ], [ %next.load, %loop1 ]
br label %loop1
loop2b: ; preds = %loop1
%gep1 = bitcast i32* %var.phi to i32*
%next.ptr = bitcast i32* %gep1 to i32**
store i32* %next.phi, i32** %next.ptr
br label %loop1
end:
ret void
}