[llvm] r373454 - Revert r373431 "Switch lowering: omit range check for bit tests when default is unreachable (PR43129)"
Hans Wennborg via llvm-commits
llvm-commits at lists.llvm.org
Wed Oct 2 05:08:45 PDT 2019
Author: hans
Date: Wed Oct 2 05:08:44 2019
New Revision: 373454
URL: http://llvm.org/viewvc/llvm-project?rev=373454&view=rev
Log:
Revert r373431 "Switch lowering: omit range check for bit tests when default is unreachable (PR43129)"
This broke http://lab.llvm.org:8011/builders/llvm-clang-x86_64-expensive-checks-win/builds/19967
> Switch lowering: omit range check for bit tests when default is unreachable (PR43129)
>
> This is modeled after the same functionality for jump tables, which was
> added in r357067.
>
> Differential revision: https://reviews.llvm.org/D68131
Modified:
llvm/trunk/include/llvm/CodeGen/SwitchLoweringUtils.h
llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
llvm/trunk/test/CodeGen/X86/switch-bt.ll
Modified: llvm/trunk/include/llvm/CodeGen/SwitchLoweringUtils.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/CodeGen/SwitchLoweringUtils.h?rev=373454&r1=373453&r2=373454&view=diff
==============================================================================
--- llvm/trunk/include/llvm/CodeGen/SwitchLoweringUtils.h (original)
+++ llvm/trunk/include/llvm/CodeGen/SwitchLoweringUtils.h Wed Oct 2 05:08:44 2019
@@ -212,14 +212,13 @@ struct BitTestBlock {
BitTestInfo Cases;
BranchProbability Prob;
BranchProbability DefaultProb;
- bool OmitRangeCheck;
BitTestBlock(APInt F, APInt R, const Value *SV, unsigned Rg, MVT RgVT, bool E,
bool CR, MachineBasicBlock *P, MachineBasicBlock *D,
BitTestInfo C, BranchProbability Pr)
: First(std::move(F)), Range(std::move(R)), SValue(SV), Reg(Rg),
RegVT(RgVT), Emitted(E), ContiguousRange(CR), Parent(P), Default(D),
- Cases(std::move(C)), Prob(Pr), OmitRangeCheck(false) {}
+ Cases(std::move(C)), Prob(Pr) {}
};
/// Return the range of values within a range.
Modified: llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp?rev=373454&r1=373453&r2=373454&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp Wed Oct 2 05:08:44 2019
@@ -2622,11 +2622,17 @@ void SelectionDAGBuilder::visitBitTestHe
// Subtract the minimum value.
SDValue SwitchOp = getValue(B.SValue);
EVT VT = SwitchOp.getValueType();
- SDValue RangeSub =
- DAG.getNode(ISD::SUB, dl, VT, SwitchOp, DAG.getConstant(B.First, dl, VT));
+ SDValue Sub = DAG.getNode(ISD::SUB, dl, VT, SwitchOp,
+ DAG.getConstant(B.First, dl, VT));
- // Determine the type of the test operands.
+ // Check range.
const TargetLowering &TLI = DAG.getTargetLoweringInfo();
+ SDValue RangeCmp = DAG.getSetCC(
+ dl, TLI.getSetCCResultType(DAG.getDataLayout(), *DAG.getContext(),
+ Sub.getValueType()),
+ Sub, DAG.getConstant(B.Range, dl, VT), ISD::SETUGT);
+
+ // Determine the type of the test operands.
bool UsePtrType = false;
if (!TLI.isTypeLegal(VT)) {
UsePtrType = true;
@@ -2639,7 +2645,6 @@ void SelectionDAGBuilder::visitBitTestHe
break;
}
}
- SDValue Sub = RangeSub;
if (UsePtrType) {
VT = TLI.getPointerTy(DAG.getDataLayout());
Sub = DAG.getZExtOrTrunc(Sub, dl, VT);
@@ -2655,24 +2660,16 @@ void SelectionDAGBuilder::visitBitTestHe
addSuccessorWithProb(SwitchBB, MBB, B.Prob);
SwitchBB->normalizeSuccProbs();
- SDValue Root = CopyTo;
- if (!B.OmitRangeCheck) {
- // Conditional branch to the default block.
- SDValue RangeCmp = DAG.getSetCC(dl,
- TLI.getSetCCResultType(DAG.getDataLayout(), *DAG.getContext(),
- RangeSub.getValueType()),
- RangeSub, DAG.getConstant(B.Range, dl, RangeSub.getValueType()),
- ISD::SETUGT);
-
- Root = DAG.getNode(ISD::BRCOND, dl, MVT::Other, Root, RangeCmp,
- DAG.getBasicBlock(B.Default));
- }
+ SDValue BrRange = DAG.getNode(ISD::BRCOND, dl,
+ MVT::Other, CopyTo, RangeCmp,
+ DAG.getBasicBlock(B.Default));
// Avoid emitting unnecessary branches to the next block.
if (MBB != NextBlock(SwitchBB))
- Root = DAG.getNode(ISD::BR, dl, MVT::Other, Root, DAG.getBasicBlock(MBB));
+ BrRange = DAG.getNode(ISD::BR, dl, MVT::Other, BrRange,
+ DAG.getBasicBlock(MBB));
- DAG.setRoot(Root);
+ DAG.setRoot(BrRange);
}
/// visitBitTestCase - this function produces one "bit test"
@@ -10167,6 +10164,8 @@ void SelectionDAGBuilder::lowerWorkItem(
break;
}
case CC_BitTests: {
+ // FIXME: If Fallthrough is unreachable, skip the range check.
+
// FIXME: Optimize away range check based on pivot comparisons.
BitTestBlock *BTB = &SL->BitTestCases[I->BTCasesIndex];
@@ -10187,11 +10186,6 @@ void SelectionDAGBuilder::lowerWorkItem(
BTB->DefaultProb -= DefaultProb / 2;
}
- if (FallthroughUnreachable) {
- // Skip the range check if the fallthrough block is unreachable.
- BTB->OmitRangeCheck = true;
- }
-
// If we're in the right place, emit the bit test header right now.
if (CurMBB == SwitchMBB) {
visitBitTestHeader(*BTB, SwitchMBB);
Modified: llvm/trunk/test/CodeGen/X86/switch-bt.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/switch-bt.ll?rev=373454&r1=373453&r2=373454&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/X86/switch-bt.ll (original)
+++ llvm/trunk/test/CodeGen/X86/switch-bt.ll Wed Oct 2 05:08:44 2019
@@ -157,12 +157,13 @@ sw.epilog:
}
-; Omit the range check when the default case is unreachable, see PR43129.
+; TODO: Omit the range check when the default case is unreachable, see PR43129.
declare void @g(i32)
define void @test5(i32 %x) {
; CHECK-LABEL: test5
-; CHECK-NOT: cmp
+; CHECK: cmpl $8, %edi
+; CHECK: ja
; 73 = 2^0 + 2^3 + 2^6
; CHECK: movl $73
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