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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. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@247958 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Quentin Colombet
parent
919b448c2e
commit
d68bf2b419
@ -313,16 +313,18 @@ void ShrinkWrap::updateSaveRestorePoints(MachineBasicBlock &MBB) {
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// for a post-dominator outside the loop.
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SmallVector<MachineBasicBlock*, 4> ExitBlocks;
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MLI->getLoopFor(Restore)->getExitingBlocks(ExitBlocks);
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if (ExitBlocks.empty()) {
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Restore = nullptr;
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break;
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// Push Restore outside of this loop.
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// Look for the immediate post-dominator of the loop exits.
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MachineBasicBlock *IPdom = Restore;
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for (MachineBasicBlock *LoopExitBB: ExitBlocks) {
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IPdom = FindIDom<>(*IPdom, LoopExitBB->successors(), *MPDT);
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if (!IPdom)
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break;
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}
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// Push Restore outside of this loop if immediate post-dominator is
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// different from restore block. If immediate post-dominator is not
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// different, bail out.
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MachineBasicBlock *IPdom =
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FindIDom<>(*Restore, Restore->successors(), *MPDT);
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if (IPdom != Restore)
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// If the immediate post-dominator is not in a less nested loop,
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// then we are stuck in a program with an infinite loop.
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// In that case, we will not find a safe point, hence, bail out.
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if (IPdom && MLI->getLoopDepth(IPdom) < MLI->getLoopDepth(Restore))
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Restore = IPdom;
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else {
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Restore = nullptr;
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@ -568,3 +568,65 @@ for.body: ; preds = %for.body, %entry
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if.end:
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ret void
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}
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; Another infinite loop test this time with a body bigger than just one block.
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; CHECK-LABEL: infiniteloop2
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; CHECK: ret
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define void @infiniteloop2() {
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entry:
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br i1 undef, label %if.then, label %if.end
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if.then:
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%ptr = alloca i32, i32 4
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br label %for.body
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for.body: ; preds = %for.body, %entry
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%sum.03 = phi i32 [ 0, %if.then ], [ %add, %body1 ], [ 1, %body2]
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%call = tail call i32 asm "mov $0, #0", "=r,~{x19}"()
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%add = add nsw i32 %call, %sum.03
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store i32 %add, i32* %ptr
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br i1 undef, label %body1, label %body2
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body1:
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tail call void asm sideeffect "nop", "~{x19}"()
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br label %for.body
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body2:
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tail call void asm sideeffect "nop", "~{x19}"()
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br label %for.body
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if.end:
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ret void
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}
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; Another infinite loop test this time with two nested infinite loop.
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; CHECK-LABEL: infiniteloop3
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; CHECK: ret
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define void @infiniteloop3() {
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entry:
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br i1 undef, label %loop2a, label %body
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body: ; preds = %entry
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br i1 undef, label %loop2a, label %end
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loop1: ; preds = %loop2a, %loop2b
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%var.phi = phi i32* [ %next.phi, %loop2b ], [ %var, %loop2a ]
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%next.phi = phi i32* [ %next.load, %loop2b ], [ %next.var, %loop2a ]
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%0 = icmp eq i32* %var, null
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%next.load = load i32*, i32** undef
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br i1 %0, label %loop2a, label %loop2b
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loop2a: ; preds = %loop1, %body, %entry
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%var = phi i32* [ null, %body ], [ null, %entry ], [ %next.phi, %loop1 ]
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%next.var = phi i32* [ undef, %body ], [ null, %entry ], [ %next.load, %loop1 ]
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br label %loop1
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loop2b: ; preds = %loop1
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%gep1 = bitcast i32* %var.phi to i32*
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%next.ptr = bitcast i32* %gep1 to i32**
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store i32* %next.phi, i32** %next.ptr
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br label %loop1
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end:
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ret void
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}
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@ -562,3 +562,65 @@ for.body: ; preds = %for.body, %entry
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if.end:
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ret void
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}
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; Another infinite loop test this time with a body bigger than just one block.
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; CHECK-LABEL: infiniteloop2
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; CHECK: pop
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define void @infiniteloop2() {
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entry:
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br i1 undef, label %if.then, label %if.end
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if.then:
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%ptr = alloca i32, i32 4
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br label %for.body
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for.body: ; preds = %for.body, %entry
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%sum.03 = phi i32 [ 0, %if.then ], [ %add, %body1 ], [ 1, %body2]
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%call = tail call i32 asm "mov $0, #0", "=r,~{r4}"()
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%add = add nsw i32 %call, %sum.03
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store i32 %add, i32* %ptr
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br i1 undef, label %body1, label %body2
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body1:
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tail call void asm sideeffect "nop", "~{r4}"()
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br label %for.body
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body2:
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tail call void asm sideeffect "nop", "~{r4}"()
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br label %for.body
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if.end:
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ret void
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}
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; Another infinite loop test this time with two nested infinite loop.
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; CHECK-LABEL: infiniteloop3
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; CHECK: bx lr
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define void @infiniteloop3() {
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entry:
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br i1 undef, label %loop2a, label %body
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body: ; preds = %entry
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br i1 undef, label %loop2a, label %end
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loop1: ; preds = %loop2a, %loop2b
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%var.phi = phi i32* [ %next.phi, %loop2b ], [ %var, %loop2a ]
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%next.phi = phi i32* [ %next.load, %loop2b ], [ %next.var, %loop2a ]
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%0 = icmp eq i32* %var, null
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%next.load = load i32*, i32** undef
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br i1 %0, label %loop2a, label %loop2b
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loop2a: ; preds = %loop1, %body, %entry
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%var = phi i32* [ null, %body ], [ null, %entry ], [ %next.phi, %loop1 ]
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%next.var = phi i32* [ undef, %body ], [ null, %entry ], [ %next.load, %loop1 ]
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br label %loop1
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loop2b: ; preds = %loop1
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%gep1 = bitcast i32* %var.phi to i32*
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%next.ptr = bitcast i32* %gep1 to i32**
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store i32* %next.phi, i32** %next.ptr
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br label %loop1
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end:
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ret void
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}
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@ -554,3 +554,65 @@ for.body: ; preds = %for.body, %entry
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if.end:
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ret void
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}
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; Another infinite loop test this time with a body bigger than just one block.
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; CHECK-LABEL: infiniteloop2
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; CHECK: blr
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define void @infiniteloop2() {
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entry:
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br i1 undef, label %if.then, label %if.end
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if.then:
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%ptr = alloca i32, i32 4
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br label %for.body
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for.body: ; preds = %for.body, %entry
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%sum.03 = phi i32 [ 0, %if.then ], [ %add, %body1 ], [ 1, %body2]
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%call = tail call i32 asm "mftb $0, 268", "=r,~{r14}"()
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%add = add nsw i32 %call, %sum.03
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store i32 %add, i32* %ptr
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br i1 undef, label %body1, label %body2
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body1:
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tail call void asm sideeffect "nop", "~{r14}"()
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br label %for.body
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body2:
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tail call void asm sideeffect "nop", "~{r14}"()
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br label %for.body
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if.end:
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ret void
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}
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; Another infinite loop test this time with two nested infinite loop.
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; CHECK-LABEL: infiniteloop3
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; CHECK: # %end
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define void @infiniteloop3() {
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entry:
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br i1 undef, label %loop2a, label %body
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body: ; preds = %entry
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br i1 undef, label %loop2a, label %end
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loop1: ; preds = %loop2a, %loop2b
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%var.phi = phi i32* [ %next.phi, %loop2b ], [ %var, %loop2a ]
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%next.phi = phi i32* [ %next.load, %loop2b ], [ %next.var, %loop2a ]
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%0 = icmp eq i32* %var, null
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%next.load = load i32*, i32** undef
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br i1 %0, label %loop2a, label %loop2b
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loop2a: ; preds = %loop1, %body, %entry
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%var = phi i32* [ null, %body ], [ null, %entry ], [ %next.phi, %loop1 ]
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%next.var = phi i32* [ undef, %body ], [ null, %entry ], [ %next.load, %loop1 ]
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br label %loop1
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loop2b: ; preds = %loop1
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%gep1 = bitcast i32* %var.phi to i32*
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%next.ptr = bitcast i32* %gep1 to i32**
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store i32* %next.phi, i32** %next.ptr
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br label %loop1
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end:
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ret void
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}
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@ -697,3 +697,35 @@ body2:
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if.end:
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ret void
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}
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; Another infinite loop test this time with two nested infinite loop.
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; CHECK-LABEL: infiniteloop3
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; CHECK: retq
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define void @infiniteloop3() {
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entry:
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br i1 undef, label %loop2a, label %body
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body: ; preds = %entry
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br i1 undef, label %loop2a, label %end
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loop1: ; preds = %loop2a, %loop2b
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%var.phi = phi i32* [ %next.phi, %loop2b ], [ %var, %loop2a ]
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%next.phi = phi i32* [ %next.load, %loop2b ], [ %next.var, %loop2a ]
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%0 = icmp eq i32* %var, null
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%next.load = load i32*, i32** undef
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br i1 %0, label %loop2a, label %loop2b
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loop2a: ; preds = %loop1, %body, %entry
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%var = phi i32* [ null, %body ], [ null, %entry ], [ %next.phi, %loop1 ]
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%next.var = phi i32* [ undef, %body ], [ null, %entry ], [ %next.load, %loop1 ]
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br label %loop1
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loop2b: ; preds = %loop1
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%gep1 = bitcast i32* %var.phi to i32*
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%next.ptr = bitcast i32* %gep1 to i32**
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store i32* %next.phi, i32** %next.ptr
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br label %loop1
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end:
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ret void
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}
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