[PATCH] D138187: [GlobalISel] Fix crash in applyShiftOfShiftedLogic caused by CSEMIRBuilder reuse instruction

[chenglin.bi via Phabricator via llvm-commits]

bcl5980 updated this revision to Diff 476329.
bcl5980 edited the summary of this revision.
bcl5980 added a comment.

58432 to 58423


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D138187/new/

https://reviews.llvm.org/D138187

Files:
  llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp
  llvm/test/CodeGen/AArch64/pr58423.ll


Index: llvm/test/CodeGen/AArch64/pr58423.ll
===================================================================
--- /dev/null
+++ llvm/test/CodeGen/AArch64/pr58423.ll
@@ -0,0 +1,15 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc < %s -mtriple=aarch64-none-linux-gnu -global-isel -global-isel-abort=0 | FileCheck %s
+
+; this used to crash
+define i32 @f(i32 %0) {
+; CHECK-LABEL: f:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    lsl w8, w0, #8
+; CHECK-NEXT:    orr w0, w8, w0, lsl #16
+; CHECK-NEXT:    ret
+  %2 = shl i32 %0, 8
+  %3 = or i32 %0, %2
+  %4 = shl i32 %3, 8
+  ret i32 %4
+}
Index: llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp
===================================================================
--- llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp
+++ llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp
@@ -1598,6 +1598,13 @@
   Register Shift1 =
       Builder.buildInstr(Opcode, {DestType}, {Shift1Base, Const}).getReg(0);
 
+  // If LogicNonShiftReg is the same to Shift1Base, and shift1 const is the same
+  // to MatchInfo.Shift2 const, CSEMIRBuilder will reuse the old shift1 when
+  // build shift2. So, if we erase MatchInfo.Shift2 at the end, actually we
+  // remove old shift1. And it will cause crash later. So erase it earlier to
+  // avoid the crash.
+  MatchInfo.Shift2->eraseFromParent();
+
   Register Shift2Const = MI.getOperand(2).getReg();
   Register Shift2 = Builder
                         .buildInstr(Opcode, {DestType},
@@ -1607,8 +1614,7 @@
   Register Dest = MI.getOperand(0).getReg();
   Builder.buildInstr(MatchInfo.Logic->getOpcode(), {Dest}, {Shift1, Shift2});
 
-  // These were one use so it's safe to remove them.
-  MatchInfo.Shift2->eraseFromParent();
+  // This was one use so it's safe to remove it.
   MatchInfo.Logic->eraseFromParent();
 
   MI.eraseFromParent();


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