[GlobalISel] Fix legalizer artifact combiner from crashing with invalid dead instructions.

The artifact combiners push instructions which have been marked for deletion
onto an list for the legalizer to deal with on return. However, for trunc(ext)
combines the combiner routine recursively calls itself. When it does this the
dead instructions list may not be empty, and the other combiners don't expect
to be dealing with essentially invalid MIR (multiple vreg defs etc).

This change fixes it by ensuring that the dead instructions are processed on
entry into tryCombineInstruction.

As a result, this fix exposed a few places in tests where G_TRUNC instructions
were not being deleted even though they were dead.

Differential Revision: https://reviews.llvm.org/D59892

llvm-svn: 357101

7 files changed, 113 insertions, 26 deletions

diff --git a/llvm/include/llvm/CodeGen/GlobalISel/LegalizationArtifactCombiner.h b/llvm/include/llvm/CodeGen/GlobalISel/LegalizationArtifactCombiner.h
index e7680e1bc12..d68704ee623 100644
--- a/llvm/include/llvm/CodeGen/GlobalISel/LegalizationArtifactCombiner.h
+++ b/llvm/include/llvm/CodeGen/GlobalISel/LegalizationArtifactCombiner.h
@@ -317,7 +317,13 @@ public:
   /// Adds instructions that are dead as a result of the combine
   /// into DeadInsts, which can include MI.
   bool tryCombineInstruction(MachineInstr &MI,
-                             SmallVectorImpl<MachineInstr *> &DeadInsts) {
+                             SmallVectorImpl<MachineInstr *> &DeadInsts,
+                             GISelObserverWrapper &WrapperObserver) {
+    // This might be a recursive call, and we might have DeadInsts already
+    // populated. To avoid bad things happening later with multiple vreg defs
+    // etc, process the dead instructions now if any.
+    if (!DeadInsts.empty())
+      deleteMarkedDeadInsts(DeadInsts, WrapperObserver);
     switch (MI.getOpcode()) {
     default:
       return false;
@@ -334,7 +340,7 @@ public:
     case TargetOpcode::G_TRUNC: {
       bool Changed = false;
       for (auto &Use : MRI.use_instructions(MI.getOperand(0).getReg()))
-        Changed |= tryCombineInstruction(Use, DeadInsts);
+        Changed |= tryCombineInstruction(Use, DeadInsts, WrapperObserver);
       return Changed;
     }
     }
@@ -395,6 +401,22 @@ private:
       DeadInsts.push_back(&DefMI);
   }
 
+  /// Erase the dead instructions in the list and call the observer hooks.
+  /// Normally the Legalizer will deal with erasing instructions that have been
+  /// marked dead. However, for the trunc(ext(x)) cases we can end up trying to
+  /// process instructions which have been marked dead, but otherwise break the
+  /// MIR by introducing multiple vreg defs. For those cases, allow the combines
+  /// to explicitly delete the instructions before we run into trouble.
+  void deleteMarkedDeadInsts(SmallVectorImpl<MachineInstr *> &DeadInsts,
+                             GISelObserverWrapper &WrapperObserver) {
+    for (auto *DeadMI : DeadInsts) {
+      LLVM_DEBUG(dbgs() << *DeadMI << "Is dead, eagerly deleting\n");
+      WrapperObserver.erasingInstr(*DeadMI);
+      DeadMI->eraseFromParentAndMarkDBGValuesForRemoval();
+    }
+    DeadInsts.clear();
+  }
+
   /// Checks if the target legalizer info has specified anything about the
   /// instruction, or if unsupported.
   bool isInstUnsupported(const LegalityQuery &Query) const {
diff --git a/llvm/lib/CodeGen/GlobalISel/Legalizer.cpp b/llvm/lib/CodeGen/GlobalISel/Legalizer.cpp
index bd486d7dd1f..4db86761cdb 100644
--- a/llvm/lib/CodeGen/GlobalISel/Legalizer.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/Legalizer.cpp
@@ -225,7 +225,8 @@ bool Legalizer::runOnMachineFunction(MachineFunction &MF) {
         continue;
       }
       SmallVector<MachineInstr *, 4> DeadInstructions;
-      if (ArtCombiner.tryCombineInstruction(MI, DeadInstructions)) {
+      if (ArtCombiner.tryCombineInstruction(MI, DeadInstructions,
+                                            WrapperObserver)) {
         for (auto *DeadMI : DeadInstructions) {
           LLVM_DEBUG(dbgs() << *DeadMI << "Is dead\n");
           RemoveDeadInstFromLists(DeadMI);
diff --git a/llvm/test/CodeGen/AArch64/GlobalISel/legalize-phi.mir b/llvm/test/CodeGen/AArch64/GlobalISel/legalize-phi.mir
index 484224f842c..6ab49ff6648 100644
--- a/llvm/test/CodeGen/AArch64/GlobalISel/legalize-phi.mir
+++ b/llvm/test/CodeGen/AArch64/GlobalISel/legalize-phi.mir
@@ -296,18 +296,17 @@ body:             |
   ; CHECK:   [[TRUNC:%[0-9]+]]:_(s16) = G_TRUNC [[C1]](s32)
   ; CHECK: bb.1:
   ; CHECK:   successors: %bb.1(0x40000000), %bb.2(0x40000000)
-  ; CHECK:   [[PHI:%[0-9]+]]:_(s16) = G_PHI [[TRUNC]](s16), %bb.0, [[TRUNC3:%[0-9]+]](s16), %bb.1
+  ; CHECK:   [[PHI:%[0-9]+]]:_(s16) = G_PHI [[TRUNC]](s16), %bb.0, [[TRUNC2:%[0-9]+]](s16), %bb.1
   ; CHECK:   [[ANYEXT:%[0-9]+]]:_(s32) = G_ANYEXT [[PHI]](s16)
   ; CHECK:   [[COPY1:%[0-9]+]]:_(s32) = COPY [[C]](s32)
   ; CHECK:   [[ADD:%[0-9]+]]:_(s32) = G_ADD [[ANYEXT]], [[COPY1]]
-  ; CHECK:   [[TRUNC1:%[0-9]+]]:_(s8) = G_TRUNC [[ADD]](s32)
   ; CHECK:   [[C2:%[0-9]+]]:_(s32) = G_CONSTANT i32 255
   ; CHECK:   [[COPY2:%[0-9]+]]:_(s32) = COPY [[ADD]](s32)
   ; CHECK:   [[AND:%[0-9]+]]:_(s32) = G_AND [[COPY2]], [[C2]]
   ; CHECK:   [[ICMP:%[0-9]+]]:_(s32) = G_ICMP intpred(ugt), [[AND]](s32), [[COPY]]
-  ; CHECK:   [[TRUNC2:%[0-9]+]]:_(s1) = G_TRUNC [[ICMP]](s32)
-  ; CHECK:   [[TRUNC3]]:_(s16) = G_TRUNC [[ADD]](s32)
-  ; CHECK:   G_BRCOND [[TRUNC2]](s1), %bb.1
+  ; CHECK:   [[TRUNC1:%[0-9]+]]:_(s1) = G_TRUNC [[ICMP]](s32)
+  ; CHECK:   [[TRUNC2]]:_(s16) = G_TRUNC [[ADD]](s32)
+  ; CHECK:   G_BRCOND [[TRUNC1]](s1), %bb.1
   ; CHECK: bb.2:
   ; CHECK:   [[C3:%[0-9]+]]:_(s32) = G_CONSTANT i32 255
   ; CHECK:   [[COPY3:%[0-9]+]]:_(s32) = COPY [[ADD]](s32)
@@ -364,14 +363,13 @@ body:             |
   ; CHECK: bb.1:
   ; CHECK:   successors: %bb.1(0x40000000), %bb.2(0x40000000)
   ; CHECK:   [[PHI:%[0-9]+]]:_(s16) = G_PHI [[TRUNC]](s16), %bb.0, [[COPY1:%[0-9]+]](s16), %bb.1
-  ; CHECK:   [[TRUNC1:%[0-9]+]]:_(s8) = G_TRUNC [[PHI]](s16)
   ; CHECK:   [[C1:%[0-9]+]]:_(s32) = G_CONSTANT i32 255
   ; CHECK:   [[ANYEXT:%[0-9]+]]:_(s32) = G_ANYEXT [[PHI]](s16)
   ; CHECK:   [[AND:%[0-9]+]]:_(s32) = G_AND [[ANYEXT]], [[C1]]
   ; CHECK:   [[ICMP:%[0-9]+]]:_(s32) = G_ICMP intpred(ugt), [[AND]](s32), [[COPY]]
-  ; CHECK:   [[TRUNC2:%[0-9]+]]:_(s1) = G_TRUNC [[ICMP]](s32)
+  ; CHECK:   [[TRUNC1:%[0-9]+]]:_(s1) = G_TRUNC [[ICMP]](s32)
   ; CHECK:   [[COPY1]]:_(s16) = COPY [[PHI]](s16)
-  ; CHECK:   G_BRCOND [[TRUNC2]](s1), %bb.1
+  ; CHECK:   G_BRCOND [[TRUNC1]](s1), %bb.1
   ; CHECK: bb.2:
   ; CHECK:   $w0 = COPY [[AND]](s32)
   ; CHECK:   RET_ReallyLR implicit $w0
@@ -547,17 +545,16 @@ body:             |
   ; CHECK:   G_BR %bb.2
   ; CHECK: bb.1:
   ; CHECK:   successors: %bb.2(0x40000000), %bb.1(0x40000000)
-  ; CHECK:   [[PHI:%[0-9]+]]:_(s16) = G_PHI [[TRUNC2]](s16), %bb.0, [[TRUNC5:%[0-9]+]](s16), %bb.1
-  ; CHECK:   [[TRUNC3:%[0-9]+]]:_(s8) = G_TRUNC [[PHI]](s16)
+  ; CHECK:   [[PHI:%[0-9]+]]:_(s16) = G_PHI [[TRUNC2]](s16), %bb.0, [[TRUNC4:%[0-9]+]](s16), %bb.1
   ; CHECK:   [[C5:%[0-9]+]]:_(s32) = G_CONSTANT i32 255
   ; CHECK:   [[ANYEXT:%[0-9]+]]:_(s32) = G_ANYEXT [[PHI]](s16)
   ; CHECK:   [[AND:%[0-9]+]]:_(s32) = G_AND [[ANYEXT]], [[C5]]
   ; CHECK:   [[ADD1:%[0-9]+]]:_(s32) = G_ADD [[AND]], [[C2]]
   ; CHECK:   [[ICMP1:%[0-9]+]]:_(s32) = G_ICMP intpred(ugt), [[ADD1]](s32), [[C3]]
-  ; CHECK:   [[TRUNC4:%[0-9]+]]:_(s1) = G_TRUNC [[ICMP1]](s32)
+  ; CHECK:   [[TRUNC3:%[0-9]+]]:_(s1) = G_TRUNC [[ICMP1]](s32)
   ; CHECK:   [[COPY2:%[0-9]+]]:_(s16) = COPY [[PHI]](s16)
-  ; CHECK:   [[TRUNC5]]:_(s16) = G_TRUNC [[C4]](s32)
-  ; CHECK:   G_BRCOND [[TRUNC4]](s1), %bb.2
+  ; CHECK:   [[TRUNC4]]:_(s16) = G_TRUNC [[C4]](s32)
+  ; CHECK:   G_BRCOND [[TRUNC3]](s1), %bb.2
   ; CHECK:   G_BR %bb.1
   ; CHECK: bb.2:
   ; CHECK:   [[PHI1:%[0-9]+]]:_(s16) = G_PHI [[COPY2]](s16), %bb.1, [[TRUNC1]](s16), %bb.0
diff --git a/llvm/test/CodeGen/AArch64/GlobalISel/legalizer-combiner-zext-trunc-crash.mir b/llvm/test/CodeGen/AArch64/GlobalISel/legalizer-combiner-zext-trunc-crash.mir
new file mode 100644
index 00000000000..391170c2dca
--- /dev/null
+++ b/llvm/test/CodeGen/AArch64/GlobalISel/legalizer-combiner-zext-trunc-crash.mir
@@ -0,0 +1,72 @@
+# NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py
+# RUN: llc -mtriple aarch64 -run-pass=legalizer -verify-machineinstrs %s -o - | FileCheck %s
+
+# This test checks we don't crash when doing zext(trunc) legalizer combines.
+---
+name:            zext_trunc_dead_inst_crash
+alignment:       2
+tracksRegLiveness: true
+body:             |
+  ; CHECK-LABEL: name: zext_trunc_dead_inst_crash
+  ; CHECK: bb.0:
+  ; CHECK:   successors: %bb.1(0x80000000)
+  ; CHECK:   [[C:%[0-9]+]]:_(s32) = G_CONSTANT i32 46
+  ; CHECK:   [[C1:%[0-9]+]]:_(s32) = G_CONSTANT i32 -33
+  ; CHECK:   [[C2:%[0-9]+]]:_(s32) = G_CONSTANT i32 -65
+  ; CHECK:   [[C3:%[0-9]+]]:_(s32) = G_CONSTANT i32 26
+  ; CHECK:   [[DEF:%[0-9]+]]:_(s16) = G_IMPLICIT_DEF
+  ; CHECK: bb.1:
+  ; CHECK:   successors: %bb.2(0x80000000)
+  ; CHECK:   [[PHI:%[0-9]+]]:_(s16) = G_PHI %33(s16), %bb.2, [[DEF]](s16), %bb.0
+  ; CHECK:   [[C4:%[0-9]+]]:_(s32) = G_CONSTANT i32 255
+  ; CHECK:   [[ANYEXT:%[0-9]+]]:_(s32) = G_ANYEXT [[PHI]](s16)
+  ; CHECK:   [[AND:%[0-9]+]]:_(s32) = G_AND [[ANYEXT]], [[C4]]
+  ; CHECK:   [[COPY:%[0-9]+]]:_(s32) = COPY [[C]](s32)
+  ; CHECK:   [[AND1:%[0-9]+]]:_(s32) = G_AND [[COPY]], [[C4]]
+  ; CHECK:   [[ICMP:%[0-9]+]]:_(s32) = G_ICMP intpred(eq), [[AND]](s32), [[AND1]]
+  ; CHECK:   [[COPY1:%[0-9]+]]:_(s32) = COPY [[ICMP]](s32)
+  ; CHECK:   [[DEF1:%[0-9]+]]:_(s32) = G_IMPLICIT_DEF
+  ; CHECK:   [[OR:%[0-9]+]]:_(s32) = G_OR [[COPY1]], [[DEF1]]
+  ; CHECK:   [[COPY2:%[0-9]+]]:_(s32) = COPY [[C1]](s32)
+  ; CHECK:   [[AND2:%[0-9]+]]:_(s32) = G_AND [[ANYEXT]], [[COPY2]]
+  ; CHECK:   [[COPY3:%[0-9]+]]:_(s32) = COPY [[AND2]](s32)
+  ; CHECK:   [[COPY4:%[0-9]+]]:_(s32) = COPY [[C2]](s32)
+  ; CHECK:   [[ADD:%[0-9]+]]:_(s32) = G_ADD [[COPY3]], [[COPY4]]
+  ; CHECK:   [[COPY5:%[0-9]+]]:_(s32) = COPY [[ADD]](s32)
+  ; CHECK:   [[AND3:%[0-9]+]]:_(s32) = G_AND [[COPY5]], [[C4]]
+  ; CHECK:   [[COPY6:%[0-9]+]]:_(s32) = COPY [[C3]](s32)
+  ; CHECK:   [[AND4:%[0-9]+]]:_(s32) = G_AND [[COPY6]], [[C4]]
+  ; CHECK:   [[ICMP1:%[0-9]+]]:_(s32) = G_ICMP intpred(ult), [[AND3]](s32), [[AND4]]
+  ; CHECK:   [[COPY7:%[0-9]+]]:_(s32) = COPY [[ICMP1]](s32)
+  ; CHECK:   [[COPY8:%[0-9]+]]:_(s32) = COPY [[OR]](s32)
+  ; CHECK:   [[OR1:%[0-9]+]]:_(s32) = G_OR [[COPY7]], [[COPY8]]
+  ; CHECK:   [[TRUNC:%[0-9]+]]:_(s1) = G_TRUNC [[OR1]](s32)
+  ; CHECK:   G_BRCOND [[TRUNC]](s1), %bb.2
+  ; CHECK: bb.2:
+  ; CHECK:   successors: %bb.1(0x80000000)
+  ; CHECK:   [[C5:%[0-9]+]]:_(s32) = G_CONSTANT i32 64
+  ; CHECK:   [[TRUNC1:%[0-9]+]]:_(s16) = G_TRUNC [[C5]](s32)
+  ; CHECK:   G_BR %bb.1
+  bb.1:
+    %1:_(s8) = G_CONSTANT i8 46
+    %3:_(s1) = G_IMPLICIT_DEF
+    %5:_(s8) = G_CONSTANT i8 -33
+    %7:_(s8) = G_CONSTANT i8 -65
+    %9:_(s8) = G_CONSTANT i8 26
+    %13:_(s8) = G_IMPLICIT_DEF
+
+  bb.2:
+    %0:_(s8) = G_PHI %12(s8), %bb.4, %13(s8), %bb.1
+    %2:_(s1) = G_ICMP intpred(eq), %0(s8), %1
+    %4:_(s1) = G_OR %2, %3
+    %6:_(s8) = G_AND %0, %5
+    %8:_(s8) = G_ADD %6, %7
+    %10:_(s1) = G_ICMP intpred(ult), %8(s8), %9
+    %11:_(s1) = G_OR %10, %4
+    G_BRCOND %11(s1), %bb.4
+
+  bb.4:
+    %12:_(s8) = G_CONSTANT i8 64
+    G_BR %bb.2
+
+...
diff --git a/llvm/test/CodeGen/AMDGPU/GlobalISel/legalize-icmp.mir b/llvm/test/CodeGen/AMDGPU/GlobalISel/legalize-icmp.mir
index ca6bbea9095..bfd7c8e12f7 100644
--- a/llvm/test/CodeGen/AMDGPU/GlobalISel/legalize-icmp.mir
+++ b/llvm/test/CodeGen/AMDGPU/GlobalISel/legalize-icmp.mir
@@ -44,7 +44,6 @@ body: |
     liveins: $vgpr0
     ; CHECK-LABEL: name: test_icmp_s16
     ; CHECK: [[C:%[0-9]+]]:_(s32) = G_CONSTANT i32 0
-    ; CHECK: [[TRUNC:%[0-9]+]]:_(s16) = G_TRUNC [[C]](s32)
     ; CHECK: [[COPY:%[0-9]+]]:_(s32) = COPY $vgpr0
     ; CHECK: [[C1:%[0-9]+]]:_(s32) = G_CONSTANT i32 65535
     ; CHECK: [[COPY1:%[0-9]+]]:_(s32) = COPY [[C]](s32)
@@ -74,7 +73,6 @@ body: |
     liveins: $vgpr0
     ; CHECK-LABEL: name: test_icmp_s8
     ; CHECK: [[C:%[0-9]+]]:_(s32) = G_CONSTANT i32 0
-    ; CHECK: [[TRUNC:%[0-9]+]]:_(s8) = G_TRUNC [[C]](s32)
     ; CHECK: [[COPY:%[0-9]+]]:_(s32) = COPY $vgpr0
     ; CHECK: [[C1:%[0-9]+]]:_(s32) = G_CONSTANT i32 255
     ; CHECK: [[COPY1:%[0-9]+]]:_(s32) = COPY [[C]](s32)
diff --git a/llvm/test/CodeGen/AMDGPU/GlobalISel/legalize-unmerge-values.mir b/llvm/test/CodeGen/AMDGPU/GlobalISel/legalize-unmerge-values.mir
index f7adb875301..c2a2bcb5bb7 100644
--- a/llvm/test/CodeGen/AMDGPU/GlobalISel/legalize-unmerge-values.mir
+++ b/llvm/test/CodeGen/AMDGPU/GlobalISel/legalize-unmerge-values.mir
@@ -211,17 +211,16 @@ body: |
     ; CHECK: [[AND1:%[0-9]+]]:_(s64) = G_AND [[ANYEXT1]], [[C2]]
     ; CHECK: [[COPY1:%[0-9]+]]:_(s64) = COPY [[SHL]](s64)
     ; CHECK: [[OR:%[0-9]+]]:_(s64) = G_OR [[AND1]], [[COPY1]]
-    ; CHECK: [[TRUNC2:%[0-9]+]]:_(s48) = G_TRUNC [[OR]](s64)
     ; CHECK: [[C3:%[0-9]+]]:_(s64) = G_CONSTANT i64 30
-    ; CHECK: [[TRUNC3:%[0-9]+]]:_(s48) = G_TRUNC [[C3]](s64)
-    ; CHECK: [[TRUNC4:%[0-9]+]]:_(s32) = G_TRUNC [[TRUNC3]](s48)
+    ; CHECK: [[TRUNC2:%[0-9]+]]:_(s48) = G_TRUNC [[C3]](s64)
+    ; CHECK: [[TRUNC3:%[0-9]+]]:_(s32) = G_TRUNC [[TRUNC2]](s48)
     ; CHECK: [[COPY2:%[0-9]+]]:_(s64) = COPY [[OR]](s64)
-    ; CHECK: [[SHL1:%[0-9]+]]:_(s64) = G_SHL [[COPY2]], [[TRUNC4]](s32)
+    ; CHECK: [[SHL1:%[0-9]+]]:_(s64) = G_SHL [[COPY2]], [[TRUNC3]](s32)
     ; CHECK: [[COPY3:%[0-9]+]]:_(s64) = COPY [[OR]](s64)
     ; CHECK: [[COPY4:%[0-9]+]]:_(s64) = COPY [[SHL1]](s64)
     ; CHECK: [[OR1:%[0-9]+]]:_(s64) = G_OR [[COPY3]], [[COPY4]]
-    ; CHECK: [[TRUNC5:%[0-9]+]]:_(s48) = G_TRUNC [[OR1]](s64)
-    ; CHECK: [[UV:%[0-9]+]]:_(s16), [[UV1:%[0-9]+]]:_(s16), [[UV2:%[0-9]+]]:_(s16) = G_UNMERGE_VALUES [[TRUNC5]](s48)
+    ; CHECK: [[TRUNC4:%[0-9]+]]:_(s48) = G_TRUNC [[OR1]](s64)
+    ; CHECK: [[UV:%[0-9]+]]:_(s16), [[UV1:%[0-9]+]]:_(s16), [[UV2:%[0-9]+]]:_(s16) = G_UNMERGE_VALUES [[TRUNC4]](s48)
     ; CHECK: [[ANYEXT2:%[0-9]+]]:_(s32) = G_ANYEXT [[UV]](s16)
     ; CHECK: [[ANYEXT3:%[0-9]+]]:_(s32) = G_ANYEXT [[UV1]](s16)
     ; CHECK: [[ANYEXT4:%[0-9]+]]:_(s32) = G_ANYEXT [[UV2]](s16)
diff --git a/llvm/test/CodeGen/Mips/GlobalISel/legalizer/sub.mir b/llvm/test/CodeGen/Mips/GlobalISel/legalizer/sub.mir
index 9f84e4d0501..3b80ca090ed 100644
--- a/llvm/test/CodeGen/Mips/GlobalISel/legalizer/sub.mir
+++ b/llvm/test/CodeGen/Mips/GlobalISel/legalizer/sub.mir
@@ -279,7 +279,6 @@ body:             |
     ; MIPS32: [[LOAD3:%[0-9]+]]:_(s32) = G_LOAD [[FRAME_INDEX3]](p0) :: (load 4 from %fixed-stack.3)
     ; MIPS32: [[SUB:%[0-9]+]]:_(s32) = G_SUB [[LOAD]], [[COPY]]
     ; MIPS32: [[ICMP:%[0-9]+]]:_(s32) = G_ICMP intpred(ult), [[LOAD]](s32), [[COPY]]
-    ; MIPS32: [[TRUNC:%[0-9]+]]:_(s1) = G_TRUNC [[ICMP]](s32)
     ; MIPS32: [[SUB1:%[0-9]+]]:_(s32) = G_SUB [[LOAD1]], [[COPY1]]
     ; MIPS32: [[C:%[0-9]+]]:_(s32) = G_CONSTANT i32 1
     ; MIPS32: [[COPY4:%[0-9]+]]:_(s32) = COPY [[ICMP]](s32)
@@ -293,7 +292,6 @@ body:             |
     ; MIPS32: [[COPY7:%[0-9]+]]:_(s32) = COPY [[ICMP1]](s32)
     ; MIPS32: [[AND1:%[0-9]+]]:_(s32) = G_AND [[COPY7]], [[C1]]
     ; MIPS32: [[SELECT:%[0-9]+]]:_(s32) = G_SELECT [[AND1]](s32), [[COPY5]], [[COPY6]]
-    ; MIPS32: [[TRUNC1:%[0-9]+]]:_(s1) = G_TRUNC [[SELECT]](s32)
     ; MIPS32: [[SUB3:%[0-9]+]]:_(s32) = G_SUB [[LOAD2]], [[COPY2]]
     ; MIPS32: [[C2:%[0-9]+]]:_(s32) = G_CONSTANT i32 1
     ; MIPS32: [[COPY8:%[0-9]+]]:_(s32) = COPY [[SELECT]](s32)