[PATCH] D133631: [X86] Fix the LEA optimization pass

[Kazu Hirata via Phabricator via llvm-commits]

kazu updated this revision to Diff 459564.
kazu added a comment.

Added a "Fixes" message.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D133631/new/

https://reviews.llvm.org/D133631

Files:
  llvm/lib/Target/X86/X86OptimizeLEAs.cpp
  llvm/test/CodeGen/X86/lea-optimize-crash.ll


Index: llvm/test/CodeGen/X86/lea-optimize-crash.ll
===================================================================
--- /dev/null
+++ llvm/test/CodeGen/X86/lea-optimize-crash.ll
@@ -0,0 +1,62 @@
+; RUN: llc -mtriple=x86_64-unknown-unknown -mcpu=x86-64 < %s | FileCheck %s
+
+; The LEA optimization pass used to crash on this testcase.
+
+target triple = "x86_64-unknown-linux-gnu"
+
+%t10 = type { i8*, [32 x i8] }
+
+; CHECK: foo:
+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)
Index: llvm/lib/Target/X86/X86OptimizeLEAs.cpp
===================================================================
--- llvm/lib/Target/X86/X86OptimizeLEAs.cpp
+++ llvm/lib/Target/X86/X86OptimizeLEAs.cpp
@@ -653,8 +653,12 @@
         // isReplaceable function.
         Register FirstVReg = First.getOperand(0).getReg();
         Register LastVReg = Last.getOperand(0).getReg();
-        for (MachineOperand &MO :
-             llvm::make_early_inc_range(MRI->use_operands(LastVReg))) {
+        // We use MRI->use_empty here instead of the combination of
+        // llvm::make_early_inc_range and MRI->use_operands because we could
+        // replace two or more uses in a debug instruction in one iteration, and
+        // that would deeply confuse llvm::make_early_inc_range.
+        while (!MRI->use_empty(LastVReg)) {
+          MachineOperand &MO = *MRI->use_begin(LastVReg);
           MachineInstr &MI = *MO.getParent();
 
           if (MI.isDebugValue()) {


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