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[Hexagon] Do not move a block if it is on a fall-through path

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llvm-svn: 301698
This commit is contained in:
Krzysztof Parzyszek 2017-04-28 21:54:11 +00:00
parent 59a03aeb7a
commit 68037e84f0
2 changed files with 81 additions and 3 deletions
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13
lib/Target/Hexagon/HexagonCFGOptimizer.cpp
View File

@ -38,6 +38,7 @@ class HexagonCFGOptimizer : public MachineFunctionPass {
private:
void InvertAndChangeJumpTarget(MachineInstr &, MachineBasicBlock *);
bool isOnFallThroughPath(MachineBasicBlock *MBB);
public:
static char ID;
@ -106,6 +107,14 @@ void HexagonCFGOptimizer::InvertAndChangeJumpTarget(
MI.getOperand(1).setMBB(NewTarget);
}
bool HexagonCFGOptimizer::isOnFallThroughPath(MachineBasicBlock *MBB) {
if (MBB->canFallThrough())
return true;
for (MachineBasicBlock *PB : MBB->predecessors())
if (PB->isLayoutSuccessor(MBB) && PB->canFallThrough())
return true;
return false;
}
bool HexagonCFGOptimizer::runOnMachineFunction(MachineFunction &Fn) {
if (skipFunction(*Fn.getFunction()))
@ -182,7 +191,6 @@ bool HexagonCFGOptimizer::runOnMachineFunction(MachineFunction &Fn) {
}
if ((NumSuccs == 2) && LayoutSucc && (LayoutSucc->pred_size() == 1)) {
// Ensure that BB2 has one instruction -- an unconditional jump.
if ((LayoutSucc->size() == 1) &&
IsUnconditionalJump(LayoutSucc->front().getOpcode())) {
@ -211,9 +219,8 @@ bool HexagonCFGOptimizer::runOnMachineFunction(MachineFunction &Fn) {
JumpAroundTarget->moveAfter(LayoutSucc);
// only move a block if it doesn't have a fall-thru. otherwise
// the CFG will be incorrect.
if (!UncondTarget->canFallThrough()) {
if (!isOnFallThroughPath(UncondTarget))
UncondTarget->moveAfter(JumpAroundTarget);
}
}
//

71
test/CodeGen/Hexagon/cfgopt-fall-through.ll Normal file
View File

@ -0,0 +1,71 @@
; RUN: llc -march=hexagon -verify-machineinstrs < %s | FileCheck %s
; REQUIRES: asserts
; Check for some sane output. This test used to crash.
; CHECK: jumpr r31
define i32 @fred(i32 %a0, i8 zeroext %a1) local_unnamed_addr #0 {
b2:
br i1 undef, label %b4, label %b3
b3: ; preds = %b2
unreachable
b4: ; preds = %b2
br i1 undef, label %b19, label %b5
b5: ; preds = %b4
br i1 undef, label %b6, label %b12
b6: ; preds = %b5
switch i8 %a1, label %b17 [
i8 2, label %b7
i8 5, label %b7
i8 1, label %b7
i8 3, label %b8
]
b7: ; preds = %b6, %b6, %b6
unreachable
b8: ; preds = %b6
br i1 undef, label %b11, label %b9
b9: ; preds = %b8
%v10 = or i32 undef, 0
br label %b15
b11: ; preds = %b8
unreachable
b12: ; preds = %b5
switch i8 %a1, label %b17 [
i8 5, label %b13
i8 1, label %b13
i8 2, label %b14
i8 3, label %b15
]
b13: ; preds = %b12, %b12
store i32 %a0, i32* undef, align 4
br label %b17
b14: ; preds = %b12
store i16 undef, i16* undef, align 4
br label %b17
b15: ; preds = %b12, %b9
%v16 = phi i32 [ 0, %b12 ], [ %v10, %b9 ]
store i32 undef, i32* undef, align 4
br label %b17
b17: ; preds = %b15, %b14, %b13, %b12, %b6
%v18 = phi i32 [ 0, %b13 ], [ 0, %b12 ], [ %v16, %b15 ], [ 0, %b14 ], [ 0, %b6 ]
ret i32 %v18
b19: ; preds = %b4
unreachable
}
attributes #0 = { nounwind "target-cpu"="hexagonv55" "target-features"="-hvx,-hvx-double,-long-calls" }