[PATCH] D125472: Fix an or+and miscompile w/ GlobalISel

[Jon Roelofs via Phabricator via llvm-commits]

jroelofs created this revision.
jroelofs added reviewers: paquette, aemerson, regehr.
Herald added subscribers: hiraditya, rovka.
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Fixes #55284


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D125472

Files:
  llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp
  llvm/test/CodeGen/AArch64/GlobalISel/combine-and-or-disjoint-mask.mir


Index: llvm/test/CodeGen/AArch64/GlobalISel/combine-and-or-disjoint-mask.mir
===================================================================
--- llvm/test/CodeGen/AArch64/GlobalISel/combine-and-or-disjoint-mask.mir
+++ llvm/test/CodeGen/AArch64/GlobalISel/combine-and-or-disjoint-mask.mir
@@ -28,6 +28,29 @@
     RET_ReallyLR implicit $w0
 ...
 ---
+name:            disjoint_masks_rev
+tracksRegLiveness: true
+machineFunctionInfo: {}
+body:             |
+  bb.0:
+    liveins: $w0
+    ; CHECK-LABEL: name: disjoint_masks_rev
+    ; CHECK: liveins: $w0
+    ; CHECK-NEXT: {{  $}}
+    ; CHECK-NEXT: %x:_(s32) = COPY $w0
+    ; CHECK-NEXT: %two:_(s32) = G_CONSTANT i32 2
+    ; CHECK-NEXT: %and:_(s32) = G_AND %x, %two
+    ; CHECK-NEXT: $w0 = COPY %and(s32)
+    ; CHECK-NEXT: RET_ReallyLR implicit $w0
+    %x:_(s32) = COPY $w0
+    %one:_(s32) = G_CONSTANT i32 1
+    %two:_(s32) = G_CONSTANT i32 2
+    %or:_(s32) = G_OR %x, %one
+    %and:_(s32) = G_AND %two, %or
+    $w0 = COPY %and(s32)
+    RET_ReallyLR implicit $w0
+...
+---
 name:            intersecting_masks
 tracksRegLiveness: true
 machineFunctionInfo: {}
@@ -53,6 +76,31 @@
     RET_ReallyLR implicit $w0
 ...
 ---
+name:            intersecting_masks_rev
+tracksRegLiveness: true
+machineFunctionInfo: {}
+body:             |
+  bb.0:
+    liveins: $w0
+    ; CHECK-LABEL: name: intersecting_masks_rev
+    ; CHECK: liveins: $w0
+    ; CHECK-NEXT: {{  $}}
+    ; CHECK-NEXT: %x:_(s32) = COPY $w0
+    ; CHECK-NEXT: %one:_(s32) = G_CONSTANT i32 3
+    ; CHECK-NEXT: %two:_(s32) = G_CONSTANT i32 2
+    ; CHECK-NEXT: %or:_(s32) = G_OR %x, %one
+    ; CHECK-NEXT: %and:_(s32) = G_AND %two, %or
+    ; CHECK-NEXT: $w0 = COPY %and(s32)
+    ; CHECK-NEXT: RET_ReallyLR implicit $w0
+    %x:_(s32) = COPY $w0
+    %one:_(s32) = G_CONSTANT i32 3
+    %two:_(s32) = G_CONSTANT i32 2
+    %or:_(s32) = G_OR %x, %one
+    %and:_(s32) = G_AND %two, %or
+    $w0 = COPY %and(s32)
+    RET_ReallyLR implicit $w0
+...
+---
 name:            disjoint_masks_v
 tracksRegLiveness: true
 machineFunctionInfo: {}
Index: llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp
===================================================================
--- llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp
+++ llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp
@@ -4225,18 +4225,23 @@
     return false;
 
   Register Src;
-  int64_t MaskAnd;
-  int64_t MaskOr;
+  Register AndMaskReg;
+  int64_t AndMaskBits;
+  int64_t OrMaskBits;
   if (!mi_match(MI, MRI,
-                m_GAnd(m_GOr(m_Reg(Src), m_ICst(MaskOr)), m_ICst(MaskAnd))))
+                m_GAnd(m_GOr(m_Reg(Src), m_ICst(OrMaskBits)),
+                       m_all_of(m_ICst(AndMaskBits), m_Reg(AndMaskReg)))))
     return false;
 
-  // Check if MaskOr could turn on any bits in Src.
-  if (MaskAnd & MaskOr)
+  // Check if OrMask could turn on any bits in Src.
+  if (AndMaskBits & OrMaskBits)
     return false;
 
   MatchInfo = [=, &MI](MachineIRBuilder &B) {
     Observer.changingInstr(MI);
+    // Canonicalize the result to have the constant on the RHS.
+    if (MI.getOperand(1).getReg() == AndMaskReg)
+      MI.getOperand(2).setReg(AndMaskReg);
     MI.getOperand(1).setReg(Src);
     Observer.changedInstr(MI);
   };


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