[PATCH] D130525: [GlobalISel] Fix miscompile of G_UREM + G_UDIV due to not checking for equality of the first operands of each.

[Amara Emerson via Phabricator via llvm-commits]

This revision was landed with ongoing or failed builds.
This revision was automatically updated to reflect the committed changes.
Closed by commit rG5ae0472694f5: [GlobalISel] Fix miscompile of G_UREM + G_UDIV due to not checking for equality (authored by aemerson).

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D130525/new/

https://reviews.llvm.org/D130525

Files:
  llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp
  llvm/test/CodeGen/AArch64/GlobalISel/combine-udivrem-use-bug.mir


Index: llvm/test/CodeGen/AArch64/GlobalISel/combine-udivrem-use-bug.mir
===================================================================
--- /dev/null
+++ llvm/test/CodeGen/AArch64/GlobalISel/combine-udivrem-use-bug.mir
@@ -0,0 +1,25 @@
+# NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py
+# RUN: llc -o - -mtriple=aarch64-unknown-unknown -run-pass=aarch64-prelegalizer-combiner -verify-machineinstrs %s | FileCheck %s
+# Check that we don't miscompile this into G_UDIVREM because of the different
+# first operands.
+---
+name:            no_combine_divrem_different_src1
+body:             |
+  bb.1:
+    liveins: $w0
+
+    ; CHECK-LABEL: name: no_combine_divrem_different_src1
+    ; CHECK: liveins: $w0
+    ; CHECK-NEXT: {{  $}}
+    ; CHECK-NEXT: [[COPY:%[0-9]+]]:_(s32) = COPY $w0
+    ; CHECK-NEXT: [[UREM:%[0-9]+]]:_(s32) = G_UREM [[COPY]], [[COPY]]
+    ; CHECK-NEXT: [[UDIV:%[0-9]+]]:_(s32) = G_UDIV [[UREM]], [[COPY]]
+    ; CHECK-NEXT: $w0 = COPY [[UDIV]](s32)
+    ; CHECK-NEXT: RET_ReallyLR implicit $w0
+    %0:_(s32) = COPY $w0
+    %1:_(s32) = G_UREM %0, %0
+    %2:_(s32) = G_UDIV %1, %0
+    $w0 = COPY %2(s32)
+    RET_ReallyLR implicit $w0
+
+...
Index: llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp
===================================================================
--- llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp
+++ llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp
@@ -1142,7 +1142,8 @@
     if (MI.getParent() == UseMI.getParent() &&
         ((IsDiv && UseMI.getOpcode() == RemOpcode) ||
          (!IsDiv && UseMI.getOpcode() == DivOpcode)) &&
-        matchEqualDefs(MI.getOperand(2), UseMI.getOperand(2))) {
+        matchEqualDefs(MI.getOperand(2), UseMI.getOperand(2)) &&
+        matchEqualDefs(MI.getOperand(1), UseMI.getOperand(1))) {
       OtherMI = &UseMI;
       return true;
     }


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