[ARM CGP] Fix ConvertTruncs

[samparker]

Summary

ConvertTruncs is used to replace a trunc for an AND mask, however this function wasn't working as expected. By performing the change later, we can create a wide type integer mask instead of a narrow -1 value, which could then be simply removed (incorrectly). Because we now perform this action later, it's necessary to cache the trunc type before we perform the promotion.

[SjoerdMeijer]

test/CodeGen/ARM/CGP/arm-cgp-casts.ll

636 ↗

(On Diff #185039)

Looks like this isn't checked... that is, if I am not mistaken, the CHECK prefix doesn't occur in the run lines?

I was initially expecting something with an AND here, but the whole point of course is that this gets optimised away? So just nitpicking on this test then.... Perhaps a CHECK udiv, followed by CHECK-NEXT mls to make this explicit, and/or possibly a CHECK-NOT and?

[samparker]

test/CodeGen/ARM/CGP/arm-cgp-casts.ll

636 ↗

(On Diff #185039)

bloody hell, if only FileCheck could tell me when I've been a buffoon...

[samparker]

Updated the test labels. The AND that is used to convert the trunc still becomes a uxtb, so we just need to check that there's one after the division.

[SjoerdMeijer]

Thanks, LGTM

llvm/trunk/lib/Target/ARM/ARMCodeGenPrepare.cpp

for (unsigned i = 0; i < I->getNumOperands(); ++i) {
         Trunc->moveBefore(I);
         I->setOperand(i, Trunc);
       }
     }
   }
 }
 
 void IRPromoter::Cleanup() {
+  LLVM_DEBUG(dbgs() << "ARM CGP: Cleanup..\n");
   // Some zexts will now have become redundant, along with their trunc
   // operands, so remove them
   for (auto V : *Visited) {
     if (!isa<ZExtInst>(V))
       continue;
 
     auto ZExt = cast<ZExtInst>(V);
     if (ZExt->getDestTy() != ExtTy)
void IRPromoter::Cleanup() {
 
   InstsToRemove.clear();
   NewInsts.clear();
   TruncTysMap.clear();
   Promoted.clear();
 }
 
 void IRPromoter::ConvertTruncs() {
+  LLVM_DEBUG(dbgs() << "ARM CGP: Converting truncs..\n");
   IRBuilder<> Builder{Ctx};
 
   for (auto *V : *Visited) {
     if (!isa<TruncInst>(V) || Sources->count(V))
       continue;
 
     auto *Trunc = cast<TruncInst>(V);
-    assert(LessThanTypeSize(Trunc) && "expected narrow trunc");
-
     Builder.SetInsertPoint(Trunc);
-    unsigned NumBits =
-      cast<IntegerType>(Trunc->getType())->getScalarSizeInBits();
-    ConstantInt *Mask = ConstantInt::get(Ctx, APInt::getMaxValue(NumBits));
+    IntegerType *SrcTy = cast<IntegerType>(Trunc->getOperand(0)->getType());
+    IntegerType *DestTy = cast<IntegerType>(TruncTysMap[Trunc][0]);
+
+    unsigned NumBits = DestTy->getScalarSizeInBits();
+    ConstantInt *Mask =
+      ConstantInt::get(SrcTy, APInt::getMaxValue(NumBits).getZExtValue());
     Value *Masked = Builder.CreateAnd(Trunc->getOperand(0), Mask);
 
     if (auto *I = dyn_cast<Instruction>(Masked))
       NewInsts.insert(I);
 
     ReplaceAllUsersOfWith(Trunc, Masked);
   }
 }
if (auto *Call = dyn_cast<CallInst>(I)) {
       }
     } else if (auto *Switch = dyn_cast<SwitchInst>(I))
       TruncTysMap[I].push_back(Switch->getCondition()->getType());
     else {
       for (unsigned i = 0; i < I->getNumOperands(); ++i)
         TruncTysMap[I].push_back(I->getOperand(i)->getType());
     }
   }
+  for (auto *V : Visited) {
+    if (!isa<TruncInst>(V) || Sources.count(V))
+      continue;
+    auto *Trunc = cast<TruncInst>(V);
+    TruncTysMap[Trunc].push_back(Trunc->getDestTy());
+  }
 
   // Convert adds and subs using negative immediates to equivalent instructions
   // that use positive constants.
   PrepareConstants();
 
   // Insert zext instructions between sources and their users.
   ExtendSources();
 
-  // Convert any truncs, that aren't sources, into AND masks.
-  ConvertTruncs();
-
   // Promote visited instructions, mutating their types in place. Also insert
   // DSP intrinsics, if enabled, for adds and subs which would be unsafe to
   // promote.
   PromoteTree();
 
+  // Convert any truncs, that aren't sources, into AND masks.
+  ConvertTruncs();
+
   // Insert trunc instructions for use by calls, stores etc...
   TruncateSinks();
 
   // Finally, remove unecessary zexts and truncs, delete old instructions and
   // clear the data structures.
   Cleanup();
 
   LLVM_DEBUG(dbgs() << "ARM CGP: Mutation complete\n");

llvm/trunk/test/CodeGen/ARM/CGP/arm-cgp-calls.ll

if.else227:
   br label %exit
 
 exit:
   %retval = phi i1 [ %cmp235, %if.then223 ], [ %cmp236, %if.else227 ]
   ret i1 %retval
 }
 
 ; CHECK-LABEL: promote_arg_pass_to_call
-; CHECK-NOT: uxt
+; CHECK: uxtb
 define i16 @promote_arg_pass_to_call(i16 zeroext %arg1, i16 zeroext %arg2) {
   %conv = add nuw i16 %arg1, 15
   %mul = mul nuw nsw i16 %conv, 3
   %cmp = icmp ult i16 %mul, %arg2
   %trunc = trunc i16 %arg1 to i8
   %res = call zeroext i16 @dummy4(i1 %cmp, i8 %trunc, i16 %arg1)
   ret i16 %res
 }

llvm/trunk/test/CodeGen/ARM/CGP/arm-cgp-casts.ll

-; RUN: llc -mtriple=thumbv8.main -mcpu=cortex-m33 %s -arm-disable-cgp=false -o - | FileCheck %s --check-prefix=CHECK-COMMON --check-prefix=CHECK-NODSP
-; RUN: llc -mtriple=thumbv7-linux-android %s -arm-disable-cgp=false -o - | FileCheck %s --check-prefix=CHECK-COMMON --check-prefix=CHECK-NODSP
-; RUN: llc -mtriple=thumbv7em %s -arm-disable-cgp=false -arm-enable-scalar-dsp=true -o - | FileCheck %s --check-prefix=CHECK-COMMON --check-prefix=CHECK-DSP
-; RUN: llc -mtriple=thumbv8 %s -arm-disable-cgp=false -arm-enable-scalar-dsp=true -arm-enable-scalar-dsp-imms=true -o - | FileCheck %s --check-prefix=CHECK-COMMON --check-prefix=CHECK-DSP-IMM
+; RUN: llc -mtriple=thumbv8.main -mcpu=cortex-m33 %s -arm-disable-cgp=false -o - | FileCheck %s --check-prefix=CHECK --check-prefix=CHECK-NODSP
+; RUN: llc -mtriple=thumbv7-linux-android %s -arm-disable-cgp=false -o - | FileCheck %s --check-prefix=CHECK --check-prefix=CHECK-NODSP
+; RUN: llc -mtriple=thumbv7em %s -arm-disable-cgp=false -arm-enable-scalar-dsp=true -o - | FileCheck %s --check-prefix=CHECK --check-prefix=CHECK-DSP
+; RUN: llc -mtriple=thumbv8 %s -arm-disable-cgp=false -arm-enable-scalar-dsp=true -arm-enable-scalar-dsp-imms=true -o - | FileCheck %s --check-prefix=CHECK --check-prefix=CHECK-DSP-IMM
 
 ; Transform will fail because the trunc is not a sink.
-; CHECK-COMMON-LABEL: dsp_trunc
-; CHECK-COMMON:   add   [[ADD:[^ ]+]],
+; CHECK-LABEL: dsp_trunc
+; CHECK:   add   [[ADD:[^ ]+]],
 ; CHECK-DSP-NEXT: ldrh  r1, [r3]
 ; CHECK-DSP-NEXT: ldrh  r2, [r2]
 ; CHECK-DSP-NEXT: subs  r1, r1, [[ADD]]
 ; CHECK-DSP-NEXT: add   r0, r2
 ; CHECK-DSP-NEXT: uxth  r3, r1
 ; CHECK-DSP-NEXT: uxth  r2, r0
 ; CHECK-DSP-NEXT: cmp   r2, r3
 
-; With DSP-IMM, we could have:
-; movs  r1, #0
-; uxth  r0, r0
-; usub16  r1, r1, r0
-; ldrh  r0, [r2]
-; ldrh  r3, [r3]
-; usub16  r0, r0, r1
-; uadd16  r1, r3, r1
-; cmp r0, r1
+; CHECK-DSP-IMM: usub16
+; CHECK-DSP-IMM: usub16
+; CHECK-DSP-IMM: uadd16
+; CHECK-DSP-IMM: cmp
 define i16 @dsp_trunc(i32 %arg0, i32 %arg1, i16* %gep0, i16* %gep1) {
 entry:
   %add0 = add i32 %arg0, %arg1
   %conv0 = trunc i32 %add0 to i16
   %sub0 = sub i16 0, %conv0
   %load0 = load i16, i16* %gep0, align 2
   %load1 = load i16, i16* %gep1, align 2
   %sub1 = sub i16 %load0, %sub0
   %add1 = add i16 %load1, %sub0
   %cmp = icmp ult i16 %sub1, %add1
   %res = select i1 %cmp, i16 %add1, i16 %sub1
   ret i16 %res
 }
 
-; CHECK-COMMON-LABEL: trunc_i16_i8
-; CHECK-COMMON: ldrh
-; CHECK-COMMON: uxtb
-; CHECK-COMMON: cmp
+; CHECK-LABEL: trunc_i16_i8
+; CHECK: ldrh
+; CHECK: uxtb
+; CHECK: cmp
 define i8 @trunc_i16_i8(i16* %ptr, i16 zeroext %arg0, i8 zeroext %arg1) {
 entry:
   %0 = load i16, i16* %ptr
   %1 = add i16 %0, %arg0
   %2 = trunc i16 %1 to i8
   %3 = icmp ugt i8 %2, %arg1
   %4 = select i1 %3, i8 %2, i8 %arg1
   ret i8 %4
 }
 
 ; The pass perform the transform, but a uxtb will still be inserted to handle
 ; the zext to the icmp.
-; CHECK-COMMON-LABEL: icmp_i32_zext:
-; CHECK-COMMON: sub
-; CHECK-COMMON: uxtb
-; CHECK-COMMON: cmp
+; CHECK-LABEL: icmp_i32_zext:
+; CHECK: sub
+; CHECK: uxtb
+; CHECK: cmp
 define i8 @icmp_i32_zext(i8* %ptr) {
 entry:
   %gep = getelementptr inbounds i8, i8* %ptr, i32 0
   %0 = load i8, i8* %gep, align 1
   %1 = sub nuw nsw i8 %0, 1
   %conv44 = zext i8 %0 to i32
   br label %preheader
 
if.end:
   %3 = load i8, i8* %gep1, align 1
   br label %body
 
 exit:
   ret i8 %2
 }
 
 ; Won't don't handle sext
-; CHECK-COMMON-LABEL: icmp_sext_zext_store_i8_i16
-; CHECK-COMMON: ldrb
-; CHECK-COMMON: ldrsh
+; CHECK-LABEL: icmp_sext_zext_store_i8_i16
+; CHECK: ldrb
+; CHECK: ldrsh
 define i32 @icmp_sext_zext_store_i8_i16() {
 entry:
   %0 = load i8, i8* getelementptr inbounds ([16 x i8], [16 x i8]* @d_uch, i32 0, i32 2), align 1
   %conv = zext i8 %0 to i16
   store i16 %conv, i16* @sh1, align 2
   %conv1 = zext i8 %0 to i32
   %1 = load i16, i16* getelementptr inbounds ([16 x i16], [16 x i16]* @d_sh, i32 0, i32 2), align 2
   %conv2 = sext i16 %1 to i32
   %cmp = icmp eq i32 %conv1, %conv2
   %conv3 = zext i1 %cmp to i32
   ret i32 %conv3
 }
 
-; CHECK-COMMON-LABEL: or_icmp_ugt:
-; CHECK-COMMON:     ldrb
-; CHECK-COMMON:     subs.w
-; CHECK-COMMON-NOT: uxt
-; CHECK-COMMON:     cmp
+; CHECK-LABEL: or_icmp_ugt:
+; CHECK:     ldrb
+; CHECK:     subs.w
+; CHECK-NOT: uxt
+; CHECK:     cmp
 define i1 @or_icmp_ugt(i32 %arg, i8* %ptr) {
 entry:
   %0 = load i8, i8* %ptr
   %1 = zext i8 %0 to i32
   %mul = shl nuw nsw i32 %1, 1
   %add0 = add nuw nsw i32 %mul, 6
   %cmp0 = icmp ne i32 %arg, %add0
   %add1 = add i8 %0, -1
   %cmp1 = icmp ugt i8 %add1, 3
   %or = or i1 %cmp0, %cmp1
   ret i1 %or
 }
 
 ; We currently only handle truncs as sinks, so a uxt will still be needed for
 ; the icmp ugt instruction.
-; CHECK-COMMON-LABEL: urem_trunc_icmps
-; CHECK-COMMON: cmp
-; CHECK-COMMON: uxt
-; CHECK-COMMON: cmp
+; CHECK-LABEL: urem_trunc_icmps
+; CHECK: cmp
+; CHECK: uxt
+; CHECK: cmp
 define void @urem_trunc_icmps(i16** %in, i32* %g, i32* %k) {
 entry:
   %ptr = load i16*, i16** %in, align 4
   %ld = load i16, i16* %ptr, align 2
   %cmp.i = icmp eq i16 %ld, 0
   br i1 %cmp.i, label %exit, label %cond.false.i
 
 cond.false.i:
for.inc:
   br label %body
 
 exit:
   ret void
 }
 
 ; Check that %exp requires uxth in all cases, and will also be required to
 ; promote %1 for the call - unless we can generate a uadd16.
-; CHECK-COMMON-LABEL: zext_load_sink_call:
-; CHECK-COMMON: uxt
+; CHECK-LABEL: zext_load_sink_call:
+; CHECK: uxt
 ; CHECK-DSP-IMM: uadd16
-; CHECK-COMMON: cmp
+; CHECK: cmp
 ; CHECK-NODSP: uxt
 ; CHECK-DSP-IMM-NOT: uxt
 define i32 @zext_load_sink_call(i16* %ptr, i16 %exp) {
 entry:
   %0 = load i16, i16* %ptr, align 4
   %1 = add i16 %exp, 3
   %cmp = icmp eq i16 %0, %exp
   br i1 %cmp, label %exit, label %if.then
 
 if.then:
   %conv0 = zext i16 %0 to i32
   %conv1 = zext i16 %1 to i32
   %call = tail call arm_aapcs_vfpcc i32 @dummy(i32 %conv0, i32 %conv1)
   br label %exit
 
 exit:
   %exitval = phi i32 [ %call, %if.then ], [ 0, %entry  ]
   ret i32 %exitval
 }
 
-; CHECK-COMMON-LABEL: bitcast_i16
-; CHECK-COMMON-NOT: uxt
+; CHECK-LABEL: bitcast_i16
+; CHECK-NOT: uxt
 define i16 @bitcast_i16(i16 zeroext %arg0, i16 zeroext %arg1) {
 entry:
   %cast = bitcast i16 12345 to i16
   %add = add nuw i16 %arg0, 1
   %cmp = icmp ule i16 %add, %cast
   %res = select i1 %cmp, i16 %arg1, i16 32657
   ret i16 %res
 }
 
-; CHECK-COMMON-LABEL: bitcast_i8
-; CHECK-COMMON-NOT: uxt
+; CHECK-LABEL: bitcast_i8
+; CHECK-NOT: uxt
 define i8 @bitcast_i8(i8 zeroext %arg0, i8 zeroext %arg1) {
 entry:
   %cast = bitcast i8 127 to i8
   %mul = shl nuw i8 %arg0, 1
   %cmp = icmp uge i8 %mul, %arg1
   %res = select i1 %cmp, i8 %cast, i8 128
   ret i8 %res
 }
 
-; CHECK-COMMON-LABEL: bitcast_i16_minus
-; CHECK-COMMON-NOT: uxt
+; CHECK-LABEL: bitcast_i16_minus
+; CHECK-NOT: uxt
 define i16 @bitcast_i16_minus(i16 zeroext %arg0, i16 zeroext %arg1) {
 entry:
   %cast = bitcast i16 -12345 to i16
   %xor = xor i16 %arg0, 7
   %cmp = icmp eq i16 %xor, %arg1
   %res = select i1 %cmp, i16 %cast, i16 32657
   ret i16 %res
 }
 
-; CHECK-COMMON-LABEL: bitcast_i8_minus
-; CHECK-COMMON-NOT: uxt
+; CHECK-LABEL: bitcast_i8_minus
+; CHECK-NOT: uxt
 define i8 @bitcast_i8_minus(i8 zeroext %arg0, i8 zeroext %arg1) {
 entry:
   %cast = bitcast i8 -127 to i8
   %and = and i8 %arg0, 3
   %cmp = icmp ne i8 %and, %arg1
   %res = select i1 %cmp, i8 %cast, i8 128
   ret i8 %res
 }
 
 declare i32 @dummy(i32, i32)
 
 @d_uch = hidden local_unnamed_addr global [16 x i8] zeroinitializer, align 1
 @sh1 = hidden local_unnamed_addr global i16 0, align 2
 @d_sh = hidden local_unnamed_addr global [16 x i16] zeroinitializer, align 2
 
-; CHECK-COMMON-LABEL: two_stage_zext_trunc_mix
-; CHECK-COMMON-NOT: uxt
+; CHECK-LABEL: two_stage_zext_trunc_mix
+; CHECK-NOT: uxt
 define i8* @two_stage_zext_trunc_mix(i32* %this, i32 %__pos1, i32 %__n1, i32** %__str, i32 %__pos2, i32 %__n2) {
 entry:
   %__size_.i.i.i.i = bitcast i32** %__str to i8*
   %0 = load i8, i8* %__size_.i.i.i.i, align 4
   %1 = and i8 %0, 1
   %tobool.i.i.i.i = icmp eq i8 %1, 0
   %__size_.i5.i.i = getelementptr inbounds i32*, i32** %__str, i32 %__n1
   %cast = bitcast i32** %__size_.i5.i.i to i32*
   %2 = load i32, i32* %cast, align 4
   %3 = lshr i8 %0, 1
   %4 = zext i8 %3 to i32
   %cond.i.i = select i1 %tobool.i.i.i.i, i32 %4, i32 %2
   %__size_.i.i.i.i.i = bitcast i32* %this to i8*
   %5 = load i8, i8* %__size_.i.i.i.i.i, align 4
   %6 = and i8 %5, 1
   %tobool.i.i.i.i.i = icmp eq i8 %6, 0
   %7 = getelementptr inbounds i8, i8* %__size_.i.i.i.i, i32 %__pos1
   %8 = getelementptr inbounds i8, i8* %__size_.i.i.i.i, i32 %__pos2
   %res = select i1 %tobool.i.i.i.i.i,  i8* %7, i8* %8
   ret i8* %res
 }
 
-; CHECK-COMMON-LABEL: search_through_zext_1
-; CHECK-COMMON-NOT: uxt
+; CHECK-LABEL: search_through_zext_1
+; CHECK-NOT: uxt
 define i8 @search_through_zext_1(i8 zeroext %a, i8 zeroext %b, i16 zeroext %c) {
 entry:
   %add = add nuw i8 %a, %b
   %conv = zext i8 %add to i16
   %cmp = icmp ult i16 %conv, %c
   br i1 %cmp, label %if.then, label %if.end
 
 if.then:
   %sub = sub nuw i8 %b, %a
   %conv2 = zext i8 %sub to i16
   %cmp2 = icmp ugt i16 %conv2, %c
   %res = select i1 %cmp2, i8 %a, i8 %b
   br label %if.end
 
 if.end:
   %retval = phi i8 [ 0, %entry ], [ %res, %if.then ]
   ret i8 %retval
 }
 
 ; TODO: We should be able to remove the uxtb here. The transform fails because
 ; the icmp ugt uses an i32, which is too large... but this doesn't matter
 ; because it won't be writing a large value to a register as a result.
-; CHECK-COMMON-LABEL: search_through_zext_2
-; CHECK-COMMON: uxtb
-; CHECK-COMMON: uxtb
+; CHECK-LABEL: search_through_zext_2
+; CHECK: uxtb
+; CHECK: uxtb
 define i8 @search_through_zext_2(i8 zeroext %a, i8 zeroext %b, i16 zeroext %c, i32 %d) {
 entry:
   %add = add nuw i8 %a, %b
   %conv = zext i8 %add to i16
   %cmp = icmp ult i16 %conv, %c
   br i1 %cmp, label %if.then, label %if.end
 
 if.then:
   %sub = sub nuw i8 %b, %a
   %conv2 = zext i8 %sub to i32
   %cmp2 = icmp ugt i32 %conv2, %d
   %res = select i1 %cmp2, i8 %a, i8 %b
   br label %if.end
 
 if.end:
   %retval = phi i8 [ 0, %entry ], [ %res, %if.then ]
   ret i8 %retval
 }
 
 ; TODO: We should be able to remove the uxtb here as all the calculations are
 ; performed on i8s. The promotion of i8 to i16 and then the later truncation
 ; results in the uxtb.
-; CHECK-COMMON-LABEL: search_through_zext_3
-; CHECK-COMMON: uxtb
-; CHECK-COMMON: uxtb
+; CHECK-LABEL: search_through_zext_3
+; CHECK: uxtb
+; CHECK: uxtb
 define i8 @search_through_zext_3(i8 zeroext %a, i8 zeroext %b, i16 zeroext %c, i32 %d) {
 entry:
   %add = add nuw i8 %a, %b
   %conv = zext i8 %add to i16
   %cmp = icmp ult i16 %conv, %c
   br i1 %cmp, label %if.then, label %if.end
 
 if.then:
   %trunc = trunc i16 %conv to i8
   %sub = sub nuw i8 %b, %trunc
   %conv2 = zext i8 %sub to i32
   %cmp2 = icmp ugt i32 %conv2, %d
   %res = select i1 %cmp2, i8 %a, i8 %b
   br label %if.end
 
 if.end:
   %retval = phi i8 [ 0, %entry ], [ %res, %if.then ]
   ret i8 %retval
 }
 
 ; TODO: We should be able to remove the uxt that gets introduced for %conv2
-; CHECK-COMMON-LABEL: search_through_zext_cmp
-; CHECK-COMMON: uxt
+; CHECK-LABEL: search_through_zext_cmp
+; CHECK: uxt
 define i8 @search_through_zext_cmp(i8 zeroext %a, i8 zeroext %b, i16 zeroext %c) {
 entry:
   %cmp = icmp ne i8 %a, %b
   %conv = zext i1 %cmp to i16
   %cmp1 = icmp ult i16 %conv, %c
   br i1 %cmp1, label %if.then, label %if.end
 
 if.then:
   %sub = sub nuw i8 %b, %a
   %conv2 = zext i8 %sub to i16
   %cmp3 = icmp ugt i16 %conv2, %c
   %res = select i1 %cmp3, i8 %a, i8 %b
   br label %if.end
 
 if.end:
   %retval = phi i8 [ 0, %entry ], [ %res, %if.then ]
   ret i8 %retval
 }
 
-; CHECK-COMMON-LABEL: search_through_zext_load
-; CHECK-COMMON-NOT: uxt
+; CHECK-LABEL: search_through_zext_load
+; CHECK-NOT: uxt
 define i8 @search_through_zext_load(i8* %a, i8 zeroext %b, i16 zeroext %c) {
 entry:
   %load = load i8, i8* %a
   %conv = zext i8 %load to i16
   %cmp1 = icmp ult i16 %conv, %c
   br i1 %cmp1, label %if.then, label %if.end
 
 if.then:
   %sub = sub nuw i8 %b, %load
   %conv2 = zext i8 %sub to i16
   %cmp3 = icmp ugt i16 %conv2, %c
   %res = select i1 %cmp3, i8 %load, i8 %b
   br label %if.end
 
 if.end:
   %retval = phi i8 [ 0, %entry ], [ %res, %if.then ]
   ret i8 %retval
 }
 
-; CHECK-COMMON-LABEL: trunc_sink_less_than
-; CHECK-COMMON-NOT: uxth
-; CHECK-COMMON: cmp
-; CHECK-COMMON: uxtb
+; CHECK-LABEL: trunc_sink_less_than
+; CHECK-NOT: uxth
+; CHECK: cmp
+; CHECK: uxtb
 define i16 @trunc_sink_less_than_cmp(i16 zeroext %a, i16 zeroext %b, i16 zeroext %c, i8 zeroext %d) {
 entry:
   %sub = sub nuw i16 %b, %a
   %cmp = icmp ult i16 %sub, %c
   br i1 %cmp, label %if.then, label %if.end
 
 if.then:
   %trunc = trunc i16 %sub to i8
   %add = add nuw i8 %d, 1
   %cmp2 = icmp ugt i8 %trunc, %add
   %res = select i1 %cmp2, i16 %a, i16 %b
   br label %if.end
 
 if.end:
   %retval = phi i16 [ 0, %entry ], [ %res, %if.then ]
   ret i16 %retval
 }
 
 ; TODO: We should be able to remove the uxth introduced to handle %sub
-; CHECK-COMMON-LABEL: trunc_sink_less_than_arith
-; CHECK-COMMON: uxth
-; CHECK-COMMON: cmp
-; CHECK-COMMON: uxtb
+; CHECK-LABEL: trunc_sink_less_than_arith
+; CHECK: uxth
+; CHECK: cmp
+; CHECK: uxtb
 define i16 @trunc_sink_less_than_arith(i16 zeroext %a, i16 zeroext %b, i16 zeroext %c, i8 zeroext %d, i8 zeroext %e) {
 entry:
   %sub = sub nuw i16 %b, %a
   %cmp = icmp ult i16 %sub, %c
   br i1 %cmp, label %if.then, label %if.end
 
 if.then:
   %trunc = trunc i16 %sub to i8
   %add = add nuw i8 %d, %trunc
   %cmp2 = icmp ugt i8 %e, %add
   %res = select i1 %cmp2, i16 %a, i16 %b
   br label %if.end
 
 if.end:
   %retval = phi i16 [ 0, %entry ], [ %res, %if.then ]
   ret i16 %retval
 }
 
-; CHECK-COMMON-LABEL: trunc_sink_less_than_store
-; CHECK-COMMON-NOT: uxt
-; CHECK-COMMON: cmp
-; CHECK-COMMON-NOT: uxt
+; CHECK-LABEL: trunc_sink_less_than_store
+; CHECK-NOT: uxt
+; CHECK: cmp
+; CHECK-NOT: uxt
 define i16 @trunc_sink_less_than_store(i16 zeroext %a, i16 zeroext %b, i16 zeroext %c, i8 zeroext %d, i8* %e) {
 entry:
   %sub = sub nuw i16 %b, %a
   %cmp = icmp ult i16 %sub, %c
   br i1 %cmp, label %if.then, label %if.end
 
 if.then:
   %trunc = trunc i16 %sub to i8
   %add = add nuw i8 %d, %trunc
   store i8 %add, i8* %e
   br label %if.end
 
 if.end:
   %retval = phi i16 [ 0, %entry ], [ %sub, %if.then ]
   ret i16 %retval
 }
 
-; CHECK-COMMON-LABEL: trunc_sink_less_than_ret
-; CHECK-COMMON-NOT: uxt
+; CHECK-LABEL: trunc_sink_less_than_ret
+; CHECK: uxt{{.*}}b
 define i8 @trunc_sink_less_than_ret(i16 zeroext %a, i16 zeroext %b, i16 zeroext %c, i8 zeroext %d, i8 zeroext %e) {
 entry:
   %sub = sub nuw i16 %b, %a
   %cmp = icmp ult i16 %sub, %c
   br i1 %cmp, label %if.then, label %if.end
 
 if.then:
   %trunc = trunc i16 %sub to i8
   %add = add nuw i8 %d, %trunc
   br label %if.end
 
 if.end:
   %retval = phi i8 [ 0, %entry ], [ %add, %if.then ]
   ret i8 %retval
 }
 
-; CHECK-COMMON-LABEL: trunc_sink_less_than_zext_ret
-; CHECK-COMMON-NOT: uxth
-; CHECK-COMMON: sub
-; CHECK-COMMON: uxtb
+; CHECK-LABEL: trunc_sink_less_than_zext_ret
+; CHECK-NOT: uxth
+; CHECK: sub
+; CHECK: uxtb
 define zeroext i8 @trunc_sink_less_than_zext_ret(i16 zeroext %a, i16 zeroext %b, i16 zeroext %c, i8 zeroext %d, i8 zeroext %e) {
 entry:
   %sub = sub nuw i16 %b, %a
   %cmp = icmp ult i16 %sub, %c
   br i1 %cmp, label %if.then, label %if.end
 
 if.then:
   %trunc = trunc i16 %sub to i8
   %add = add nuw i8 %d, %trunc
   br label %if.end
 
 if.end:
   %retval = phi i8 [ 0, %entry ], [ %add, %if.then ]
   ret i8 %retval
 }
 
-; CHECK-COMMON-LABEL: bitcast_i1
-; CHECK-COMMON-NOT: uxt
+; CHECK-LABEL: bitcast_i1
+; CHECK-NOT: uxt
 define i32 @bitcast_i1(i16 zeroext %a, i32 %b, i32 %c) {
 entry:
   %0 = bitcast i1 1 to i1
   %1 = trunc i16 %a to i1
   %cmp = icmp eq i1 %1, %0
   br i1 %cmp, label %if.then, label %exit
 
 if.then:
   %conv = zext i1 %0 to i16
   %conv1 = zext i1 %1 to i16
   %cmp1 = icmp uge i16 %conv, %conv1
   %select = select i1 %cmp1, i32 %b, i32 %c
   br label %exit
 
 exit:
   %retval = phi i32 [ %select, %if.then ], [ 0, %entry ]
   ret i32 %retval
 }
 
-; CHECK-COMMON-LABEL: search_back_through_trunc
-; CHECK-COMMON-NOT: uxt
-; CHECK-COMMON: cmp
-; CHECK-COMMON: strb
-; CHECK-COMMON: strb
+; CHECK-LABEL: search_back_through_trunc
+; CHECK-NOT: uxt
+; CHECK: cmp
+; CHECK: strb
+; CHECK: strb
 define void @search_back_through_trunc(i8* %a, i8* %b, i8* %c, i8* %d, i16* %e) {
 entry:
   %0 = load i8, i8* %a, align 1
   %conv106 = zext i8 %0 to i16
   %shl = shl nuw i16 %conv106, 8
   %1 = load i8, i8* %b, align 1
   %conv108 = zext i8 %1 to i16
   %or109 = or i16 %shl, %conv108

 
 cond.end:
   %cond = phi i8 [ %rem.zext, %cond.false ], [ %1, %entry ]
   store i8 %cond, i8* @a, align 1
   ret void
 }
 
 ; CHECK-LABEL: dont_replace_trunc_1
-; CHECK: cmp
+; CHECK: sxth
 ; CHECK: uxtb
-define void @dont_replace_trunc_1(i8* %a, i16* %b, i16* %c, i32* %d, i8* %e, i32* %f) {
+; CHECK: uxth
+define i1 @dont_replace_trunc_1(i8* %a, i16* %b, i16* %c, i32* %d, i8* %e, i32* %f) {
 entry:
   %0 = load i16, i16* %c, align 2
   %1 = load i16, i16* %b, align 2
   %conv = sext i16 %1 to i32
   store i32 %conv, i32* %f, align 4
   %2 = trunc i16 %1 to i8
   %conv1 = and i8 %2, 1
   store i8 %conv1, i8* %e, align 1
   %3 = load i8, i8* %a, align 1
   %narrow = mul nuw i8 %3, %conv1
   %mul = zext i8 %narrow to i32
   store i32 %mul, i32* %d, align 4
   %4 = zext i8 %narrow to i16
   %conv5 = or i16 %0, %4
   %tobool = icmp eq i16 %conv5, 0
-  br i1 %tobool, label %if.end, label %for.cond
-
-for.cond:                                         ; preds = %entry, %for.cond
-  br label %for.cond
-
-if.end:                                           ; preds = %entry
-  ret void
+  ret i1 %tobool
 }
 
 ; CHECK-LABEL: dont_replace_trunc_2
 ; CHECK: cmp
 ; CHECK: uxtb
 define i32 @dont_replace_trunc_2(i16* %a, i8* %b) {
 entry:
   %0 = load i16, i16* %a, align 2
   %cmp = icmp ugt i16 %0, 8
   %narrow = select i1 %cmp, i16 %0, i16 0
   %cond = trunc i16 %narrow to i8
   %1 = load i8, i8* %b, align 1
   %or = or i8 %1, %cond
   store i8 %or, i8* %b, align 1
   %conv5 = zext i8 %or to i32
   ret i32 %conv5
 }
+
+; CHECK-LABEL: replace_trunk_with_mask
+; CHECK: div
+; CHECK: uxtb
+define i32 @replace_trunk_with_mask(i16* %a) {
+entry:
+  %0 = load i16, i16* %a
+  %cmp = icmp eq i16 %0, 0
+  br i1 %cmp, label %cond.end, label %cond.false
+
+cond.false:
+  %1 = urem i16 535, %0
+  %.lhs.trunc = trunc i16 %1 to i8
+  %2 = udiv i8 %.lhs.trunc, 3
+  %phitmp = zext i8 %2 to i32
+  br label %cond.end
+
+cond.end:
+  %cond = phi i32 [ %phitmp, %cond.false ], [ 0, %entry ]
+  ret i32 %cond
+}