Crash in the x86 LEA optimization pass

[kazutakahirata]

Build a compiler at 23dec4a3524aa5c9cc3cb401987014c6c5ee9de0 for x86-64.

Compile the attached test case with the resulting compiler on a x86-64 machine:

$ clang -O3 -S reduced.ll -o reduced.s

You'll encounter:

clang: /.../llvm/lib/Target/X86/X86OptimizeLEAs.cpp:695: bool (anonymous
namespace)::X86OptimizeLEAPass::removeRedundantLEAs((anonymous namespace)::X86OptimizeLEAPass::MemOpMap &):
Assertion `MRI->use_empty(LastVReg) && "The LEA's def register must have no uses"' failed.

I've posted an analysis and possible fix at https://reviews.llvm.org/D133631

The revisions after the aforementioned revision do not trigger the bug, but I don't think the underlying issue has gone away. reduced.txt

[llvmbot]

@llvm/issue-subscribers-backend-x86

[RKSimon]

This is the best reduction I've managed so far:

target triple = "x86_64-unknown-linux-gnu"

%t10 = type { i8*, [32 x i8] }

define void @foo() {
bb_entry:
  %tmp11 = alloca [0 x [0 x i32]], i32 0, align 4
  %i = alloca %t10, align 8
  %i1 = alloca %t10, align 8
  %tmp1.sub = getelementptr inbounds [0 x [0 x i32]], [0 x [0 x i32]]* %tmp11, i64 0, i64 0, i64 0
  %i2 = bitcast [0 x [0 x i32]]* %tmp11 to i8*
  br label %bb_8

bb_8:                                             ; preds = %bb_last, %bb_entry
  br i1 undef, label %bb_last, label %bb_mid

bb_mid:                                           ; preds = %bb_8
  %i3 = bitcast %t10* %i1 to i8*
  %i4 = getelementptr inbounds %t10, %t10* %i1, i64 0, i32 1, i64 32
  %i5 = bitcast %t10* %i to i8*
  %i6 = getelementptr inbounds %t10, %t10* %i, i64 0, i32 1, i64 32
  call void @llvm.lifetime.start.p0i8(i64 0, i8* nonnull %i3)
  %v21 = call i64 @llvm.ctlz.i64(i64 undef, i1 false)
  call void @llvm.memcpy.p0i8.p0i8.i64(i8* noundef nonnull dereferenceable(16) null, i8* noundef nonnull align 8 dereferenceable(16) %i4, i64 16, i1 false)
  call void @llvm.dbg.value(metadata !DIArgList(i8* %i4, i8* %i4), metadata !4, metadata !DIExpression(DW_OP_LLVM_arg, 0)), !dbg !9
  call void @llvm.lifetime.end.p0i8(i64 0, i8* nonnull %i3)
  call void @llvm.lifetime.start.p0i8(i64 0, i8* nonnull %i5)
  call void @llvm.memcpy.p0i8.p0i8.i64(i8* noundef nonnull dereferenceable(16) null, i8* noundef nonnull align 8 dereferenceable(16) %i6, i64 16, i1 false)
  call void @llvm.lifetime.end.p0i8(i64 0, i8* nonnull %i5)
  br label %bb_last

bb_last:                                          ; preds = %bb_mid, %bb_8
  call void @llvm.lifetime.start.p0i8(i64 0, i8* nonnull %i2)
  call void undef(i32* null, i32* null, i32* null, i32 0, i32* nonnull %tmp1.sub)
  call void @llvm.lifetime.end.p0i8(i64 0, i8* nonnull %i2)
  br label %bb_8
}

declare i64 @llvm.ctlz.i64(i64, i1 immarg)
declare void @llvm.memcpy.p0i8.p0i8.i64(i8* noalias nocapture writeonly, i8* noalias nocapture readonly, i64, i1 immarg)
declare void @llvm.lifetime.start.p0i8(i64 immarg, i8* nocapture)
declare void @llvm.lifetime.end.p0i8(i64 immarg, i8* nocapture)
declare void @llvm.dbg.value(metadata, metadata, metadata)

!llvm.dbg.cu = !{!0}
!llvm.module.flags = !{!2}

!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_14, file: !1, isOptimized: false, runtimeVersion: 0, emissionKind: NoDebug)
!1 = !DIFile(filename: "n", directory: "/proc/self/cwd", checksumkind: CSK_MD5, checksum: "e588179fedd8fcdfada963f2434cb950")
!2 = !{i32 2, !"Debug Info Version", i32 3}
!3 = !{!"function_entry_count", i64 2423}
!4 = !DILocalVariable(name: "r", scope: !5, file: !6, line: 93)
!5 = distinct !DISubprogram(name: "c", scope: !7, file: !6, line: 92, spFlags: DISPFlagDefinition, unit: !0)
!6 = !DIFile(filename: "a", directory: "/proc/self/cwd")
!7 = !DINamespace(name: "u", scope: !8)
!8 = !DINamespace(name: "s", scope: null)
!9 = !DILocation(line: 0, scope: !5)