[PowerPC] Handle constant zero bits in BitPermutationSelector

[nemanjai]

Summary

We currently crash when analyzing an AssertZExt node that has some bits that are constant zeros (i.e. as a result of an and with a constant).

This issue was reported in https://bugs.llvm.org/show_bug.cgi?id=41088 and this patch fixes that.

[merge_guards_bot]

Unit tests: pass. 61162 tests passed, 0 failed and 728 were skipped.

clang-tidy: fail. Please fix clang-tidy findings.

clang-format: fail. Please format your changes with clang-format by running git-clang-format HEAD^ or applying this patch.

Build artifacts: diff.json, clang-tidy.txt, clang-format.patch, CMakeCache.txt, console-log.txt, test-results.xml

[nemanjai]

Run git-clang-format.
I don't want to address the clang-tidy check results as I don't really want to change the induction variable from i to I. The former is ubiquitous.

[merge_guards_bot]

Unit tests: pass. 61163 tests passed, 0 failed and 728 were skipped.

clang-tidy: fail. Please fix clang-tidy findings.

clang-format: pass.

Build artifacts: diff.json, clang-tidy.txt, clang-format.patch, CMakeCache.txt, console-log.txt, test-results.xml

[hfinkel]

LGTM

llvm/lib/Target/PowerPC/PPCISelDAGToDAG.cpp

case ISD::AssertZext: {
       // For AssertZext, we look through the operand and
       // mark the bits known to be zero.
       const SmallVector<ValueBit, 64> *LHSBits;
       std::tie(Interesting, LHSBits) = getValueBits(V.getOperand(0),
                                                     NumBits);
 
       EVT FromType = cast<VTSDNode>(V.getOperand(1))->getVT();
       const unsigned NumValidBits = FromType.getSizeInBits();
       for (unsigned i = 0; i < NumValidBits; ++i)
         Bits[i] = (*LHSBits)[i];
 
-      // These bits are known to be zero.
+      // These bits are known to be zero but the AssertZext may be from a value
+      // that already has some constant zero bits (i.e. from a masking and).
       for (unsigned i = NumValidBits; i < NumBits; ++i)
-        Bits[i] = ValueBit((*LHSBits)[i].getValue(),
+        Bits[i] = (*LHSBits)[i].hasValue()
+                      ? ValueBit((*LHSBits)[i].getValue(),
                                  (*LHSBits)[i].getValueBitIndex(),
-                           ValueBit::VariableKnownToBeZero);
+                                 ValueBit::VariableKnownToBeZero)
+                      : ValueBit(ValueBit::ConstZero);
 
       return std::make_pair(Interesting, &Bits);
     }
     case ISD::LOAD:
       LoadSDNode *LD = cast<LoadSDNode>(V);
       if (ISD::isZEXTLoad(V.getNode()) && V.getResNo() == 0) {
         EVT VT = LD->getMemoryVT();
         const unsigned NumValidBits = VT.getSizeInBits();

llvm/test/CodeGen/PowerPC/pr41088.ll

+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc -mcpu=pwr8 -ppc-asm-full-reg-names \
+; RUN:   -mtriple=powerpc64le-unknown-unknown -verify-machineinstrs < %s | \
+; RUN:   FileCheck %s
+
+%0 = type { [0 x i64], %1, [0 x i64], { i64, i8* }, [0 x i64] }
+%1 = type { [0 x i64], %2, [0 x i64], i64*, [0 x i64] }
+%2 = type { [0 x i64], %3, [0 x i64], %4, [0 x i8], i8, [7 x i8] }
+%3 = type { [0 x i64], { i64*, i64* }, [0 x i64], i64*, [0 x i8], i8, [7 x i8] }
+%4 = type { [0 x i64], { i64*, i64* }, [0 x i64], %5, [0 x i64] }
+%5 = type { [0 x i64], { i64*, i64* }, [0 x i64], i64*, [0 x i64] }
+%6 = type { [0 x i64], i64, [2 x i64] }
+%7 = type { [0 x i64], { i64*, i64* }, [0 x i64], %8, [0 x i64] }
+%8 = type { [0 x i64], %9*, [0 x i32], { i32, i32 }, [0 x i8], i8, [7 x i8] }
+%9 = type { [0 x i64], i64, [0 x i64], [0 x %10], [0 x i8], %11 }
+%10 = type { [0 x i8], i8, [31 x i8] }
+%11 = type {}
+%12 = type { [0 x i64], %13, [0 x i32], i32, [0 x i32], i32, [0 x i32] }
+%13 = type { [0 x i8], i8, [23 x i8] }
+%14 = type { [0 x i64], i64, [0 x i64], %15, [0 x i32], i32, [0 x i8], i8, [0 x i8], { i8, i8 }, [0 x i8], { i8, i8 }, [0 x i8], { i8, i8 }, [0 x i8], { i8, i8 }, [0 x i8], { i8, i8 }, [0 x i8], { i8, i8 }, [0 x i8], { i8, i8 }, [0 x i8], { i8, i8 }, [0 x i8], { i8, i8 }, [0 x i8], { i8, i8 }, [7 x i8] }
+%15 = type { [0 x i64], { i64*, i64 }, [0 x i64], i64, [0 x i64] }
+%16 = type { [0 x i64], %17, [0 x i64], %18, [0 x i64], %19, [0 x i64], i64, [0 x i8], { i8, i8 }, [6 x i8] }
+%17 = type { [0 x i32], i32, [27 x i32] }
+%18 = type { [0 x i64], i64, [6 x i64] }
+%19 = type { [0 x i8], i8, [103 x i8] }
+%20 = type { [0 x i64], { i64*, i64* }*, [0 x i64], %7**, [0 x i64], i64**, [0 x i64] }
+%21 = type { [0 x i64], i64, [0 x i64], void (i32, %21*)*, [0 x i64], [2 x i64], [0 x i64] }
+%22 = type { [0 x i8] }
+
+@var = external dso_local unnamed_addr constant <{ i8*, [8 x i8], i8*, [16 x i8] }>, align 8
+
+declare dso_local fastcc { i64*, i8* } @test2(%0**) unnamed_addr
+
+define void @test(%6* %arg, %7* %arg1, %12* %arg2) unnamed_addr personality i32 (i32, i32, i64, %21*, %22*)* @personality {
+; CHECK-LABEL: test:
+; CHECK:         .cfi_personality 148, DW.ref.personality
+; CHECK-NEXT:    .cfi_lsda 20, .Lexception0
+; CHECK-NEXT:  .Lfunc_gep0:
+; CHECK-NEXT:    addis r2, r12, .TOC.-.Lfunc_gep0@ha
+; CHECK-NEXT:    addi r2, r2, .TOC.-.Lfunc_gep0@l
+; CHECK-NEXT:  .Lfunc_lep0:
+; CHECK-NEXT:    .localentry test, .Lfunc_lep0-.Lfunc_gep0
+; CHECK-NEXT:  # %bb.0: # %bb
+; CHECK-NEXT:    mflr r0
+; CHECK-NEXT:    std r0, 16(r1)
+; CHECK-NEXT:    stdu r1, -32(r1)
+; CHECK-NEXT:    .cfi_def_cfa_offset 32
+; CHECK-NEXT:    .cfi_offset lr, 16
+; CHECK-NEXT:    li r3, 0
+; CHECK-NEXT:  # %bb.1: # %bb9
+; CHECK-NEXT:    bl test5
+; CHECK-NEXT:    nop
+; CHECK-NEXT:    rlwinm r3, r3, 8, 16, 23
+; CHECK-NEXT:  # %bb.2: # %bb12
+; CHECK-NEXT:    clrldi r4, r3, 32
+; CHECK-NEXT:    bl test3
+; CHECK-NEXT:    addi r1, r1, 32
+; CHECK-NEXT:    ld r0, 16(r1)
+; CHECK-NEXT:    mtlr r0
+; CHECK-NEXT:    blr
+bb:
+  switch i64 undef, label %bb21 [
+    i64 3, label %bb3
+  ]
+
+bb3:                                              ; preds = %bb
+  switch i3 undef, label %bb4 [
+    i3 0, label %bb9
+    i3 1, label %bb12
+  ]
+
+bb4:                                              ; preds = %bb3
+  unreachable
+
+bb5:                                              ; No predecessors!
+  br label %bb12
+
+bb6:                                              ; No predecessors!
+  br label %bb12
+
+bb7:                                              ; No predecessors!
+  br label %bb12
+
+bb8:                                              ; No predecessors!
+  br label %bb12
+
+bb9:                                              ; preds = %bb3
+  %tmp = call i8 @test5(%14* noalias nonnull readonly align 8 dereferenceable(64) undef), !range !0
+  %tmp10 = zext i8 %tmp to i24
+  %tmp11 = shl nuw nsw i24 %tmp10, 8
+  br label %bb12
+
+bb12:                                             ; preds = %bb9, %bb8, %bb7, %bb6, %bb5, %bb3
+  %tmp13 = phi i24 [ 1024, %bb8 ], [ 768, %bb7 ], [ 512, %bb6 ], [ 256, %bb5 ], [ %tmp11, %bb9 ], [ 0, %bb3 ]
+  %tmp14 = call fastcc align 8 dereferenceable(288) %16* @test3(%20* noalias nonnull readonly align 8 dereferenceable(24) undef, i24 %tmp13)
+  br label %bb22
+
+bb15:                                             ; No predecessors!
+  %tmp16 = invoke fastcc { i64*, i8* } @test2(%0** nonnull align 8 dereferenceable(8) undef)
+          to label %bb17 unwind label %bb18
+
+bb17:                                             ; preds = %bb15
+  invoke void @test4({ [0 x i64], { [0 x i8]*, i64 }, [0 x i64], { [0 x i8]*, i64 }, [0 x i32], i32, [0 x i32], i32, [0 x i32] }* noalias readonly align 8 dereferenceable(40) bitcast (<{ i8*, [8 x i8], i8*, [16 x i8] }>* @var to { [0 x i64], { [0 x i8]*, i64 }, [0 x i64], { [0 x i8]*, i64 }, [0 x i32], i32, [0 x i32], i32, [0 x i32] }*))
+          to label %bb23 unwind label %bb25
+
+bb18:                                             ; preds = %bb15
+  %tmp19 = landingpad { i8*, i32 }
+          cleanup
+  resume { i8*, i32 } undef
+
+bb20:                                             ; No predecessors!
+  invoke void @test4({ [0 x i64], { [0 x i8]*, i64 }, [0 x i64], { [0 x i8]*, i64 }, [0 x i32], i32, [0 x i32], i32, [0 x i32] }* noalias readonly align 8 dereferenceable(40) bitcast (<{ i8*, [8 x i8], i8*, [16 x i8] }>* @var to { [0 x i64], { [0 x i8]*, i64 }, [0 x i64], { [0 x i8]*, i64 }, [0 x i32], i32, [0 x i32], i32, [0 x i32] }*))
+          to label %bb24 unwind label %bb25
+
+bb21:                                             ; preds = %bb
+  unreachable
+
+bb22:                                             ; preds = %bb12
+  ret void
+
+bb23:                                             ; preds = %bb17
+  unreachable
+
+bb24:                                             ; preds = %bb20
+  unreachable
+
+bb25:                                             ; preds = %bb20, %bb17
+  %tmp26 = landingpad { i8*, i32 }
+          cleanup
+  resume { i8*, i32 } undef
+}
+
+declare dso_local fastcc %16* @test3(%20*, i24) unnamed_addr
+
+declare i32 @personality(i32, i32, i64, %21*, %22*) unnamed_addr
+
+declare void @test4({ [0 x i64], { [0 x i8]*, i64 }, [0 x i64], { [0 x i8]*, i64 }, [0 x i32], i32, [0 x i32], i32, [0 x i32] }*) unnamed_addr
+
+declare i8 @test5(%14*) unnamed_addr
+
+!0 = !{i8 0, i8 5}