diff options
| -rw-r--r-- | llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp | 38 | ||||
| -rw-r--r-- | llvm/test/CodeGen/X86/switch.ll | 34 |
2 files changed, 58 insertions, 14 deletions
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp index d5171442fbf..93b3b72e956 100644 --- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp +++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp @@ -1675,14 +1675,23 @@ SelectionDAGISel::FinishBasicBlock() { // If all cases cover a contiguous range, it is not necessary to jump to // the default block after the last bit test fails. This is because the // range check during bit test header creation has guaranteed that every - // case here doesn't go outside the range. + // case here doesn't go outside the range. In this case, there is no need + // to perform the last bit test, as it will always be true. Instead, make + // the second-to-last bit-test fall through to the target of the last bit + // test, and delete the last bit test. + MachineBasicBlock *NextMBB; - if (BTB.ContiguousRange && j + 2 == ej) + if (BTB.ContiguousRange && j + 2 == ej) { + // Second-to-last bit-test with contiguous range: fall through to the + // target of the final bit test. NextMBB = BTB.Cases[j + 1].TargetBB; - else if (j + 1 != ej) - NextMBB = BTB.Cases[j + 1].ThisBB; - else + } else if (j + 1 == ej) { + // For the last bit test, fall through to Default. NextMBB = BTB.Default; + } else { + // Otherwise, fall through to the next bit test. + NextMBB = BTB.Cases[j + 1].ThisBB; + } SDB->visitBitTestCase(BTB, NextMBB, UnhandledProb, BTB.Reg, BTB.Cases[j], FuncInfo->MBB); @@ -1691,8 +1700,11 @@ SelectionDAGISel::FinishBasicBlock() { SDB->clear(); CodeGenAndEmitDAG(); - if (BTB.ContiguousRange && j + 2 == ej) + if (BTB.ContiguousRange && j + 2 == ej) { + // Since we're not going to use the final bit test, remove it. + BTB.Cases.pop_back(); break; + } } // Update PHI Nodes @@ -1703,12 +1715,14 @@ SelectionDAGISel::FinishBasicBlock() { assert(PHI->isPHI() && "This is not a machine PHI node that we are updating!"); // This is "default" BB. We have two jumps to it. From "header" BB and - // from last "case" BB. - if (PHIBB == BTB.Default) - PHI.addReg(FuncInfo->PHINodesToUpdate[pi].second) - .addMBB(BTB.Parent) - .addReg(FuncInfo->PHINodesToUpdate[pi].second) - .addMBB(BTB.Cases.back().ThisBB); + // from last "case" BB, unless the latter was skipped. + if (PHIBB == BTB.Default) { + PHI.addReg(FuncInfo->PHINodesToUpdate[pi].second).addMBB(BTB.Parent); + if (!BTB.ContiguousRange) { + PHI.addReg(FuncInfo->PHINodesToUpdate[pi].second) + .addMBB(BTB.Cases.back().ThisBB); + } + } // One of "cases" BB. for (unsigned j = 0, ej = BTB.Cases.size(); j != ej; ++j) { diff --git a/llvm/test/CodeGen/X86/switch.ll b/llvm/test/CodeGen/X86/switch.ll index 5bba78d4490..2506a075106 100644 --- a/llvm/test/CodeGen/X86/switch.ll +++ b/llvm/test/CodeGen/X86/switch.ll @@ -1,5 +1,5 @@ -; RUN: llc -mtriple=x86_64-linux-gnu %s -o - -jump-table-density=40 | FileCheck %s -; RUN: llc -mtriple=x86_64-linux-gnu %s -o - -O0 -jump-table-density=40 | FileCheck --check-prefix=NOOPT %s +; RUN: llc -mtriple=x86_64-linux-gnu %s -o - -jump-table-density=40 -verify-machineinstrs | FileCheck %s +; RUN: llc -mtriple=x86_64-linux-gnu %s -o - -O0 -jump-table-density=40 -verify-machineinstrs | FileCheck --check-prefix=NOOPT %s declare void @g(i32) @@ -748,3 +748,33 @@ return: ret void ; Don't assert due to truncating the bitwidth (64) to i4 when checking ; that the bit-test range fits in a word. } + + +define i32 @pr27132(i32 %i) { +entry: + br i1 undef, label %sw, label %end +sw: + switch i32 %i, label %end [ + i32 99, label %sw.bb + i32 98, label %sw.bb + i32 101, label %sw.bb + i32 97, label %sw.bb2 + i32 96, label %sw.bb2 + i32 100, label %sw.bb2 + ] +sw.bb: + unreachable +sw.bb2: + unreachable +end: + %p = phi i32 [ 1, %sw ], [ 0, %entry ] + ret i32 %p + +; CHECK-LABEL: pr27132: +; The switch is lowered with bit tests. Since the case range is contiguous, the +; second bit test is redundant and can be skipped. Check that we don't update +; the phi node with an incoming value from the MBB of the skipped bit test +; (-verify-machine-instrs cathces this). +; CHECK: btl +; CHECK-NOT: btl +} |
