[ARM][ParallelDSP] SExt mul for accumulation

[samparker]

Summary

For any unpaired muls, we accumulate them as an input to the reduction. Check the type of the mul and perform a sext if the existing accumlator input type is not the same.

[efriedma]

Could you describe the complete flow here? If getAccumulator() returns a value, I think I see how it works; the type of that value is the type of the final accumulator, and you need to sign-extend multiplies to match that type. If getAccumulator() returns null, I don't see how this is supposed to work; it looks like the code arbitrarily decides the accumulator should be 32 bits.

[samparker]

Bah! You're right, it doesn't make sense and there wasn't a test for it... I'm now querying the root for the type and creating the right zero accumulator input if needed. Added more 64-bit tests too.

[efriedma]

LGTM

lib/Target/ARM/ARMParallelDSP.cpp

   // as before.
   IRBuilder<NoFolder> Builder(InsertAfter->getParent(),
                               ++BasicBlock::iterator(InsertAfter));
   MulCandList &MulCands = R.getMuls();
   for (auto &MulCand : MulCands) {
     if (MulCand->Paired)
       continue;
 
-    LLVM_DEBUG(dbgs() << "Accumulating unpaired mul: " << *MulCand->Root
-               << "\n");
+    Value *Mul = MulCand->Root;
+    LLVM_DEBUG(dbgs() << "Accumulating unpaired mul: " << *Mul << "\n");
     if (!Acc) {
-      Acc = MulCand->Root;
+      Acc = Mul;
       continue;
     }
-    Acc = Builder.CreateAdd(MulCand->Root, Acc);
+
+    if (Acc->getType() != Mul->getType()) {
+      assert(Acc->getType()->isIntegerTy(64) &&
+             "expected 64-bit accumulator input");
+      Mul = Builder.CreateSExt(Mul, Acc->getType());
+    }
+
+    Acc = Builder.CreateAdd(Mul, Acc);
     InsertAfter = cast<Instruction>(Acc);
   }
 
   if (!Acc)
     Acc = ConstantInt::get(IntegerType::get(M->getContext(), 32), 0);
 
   IntegerType *Ty = IntegerType::get(M->getContext(), 32);
   for (auto &Pair : R.getMulPairs()) {

test/CodeGen/ARM/ParallelDSP/pr43073.ll

entry:
   %arrayidx27 = getelementptr inbounds i16, i16* %b, i32 5
   %ld.11 = load i16, i16* %arrayidx27, align 2
   %conv28 = sext i16 %ld.11 to i32
   %mul29 = mul nsw i32 %conv28, %conv26
   %add30 = add i32 %add24, %mul29
   ret i32 %add30
 }
 
+; CHECK-LABEL: with_64bit_acc
+; CHECK: [[ADDR_IN_MINUS_1:%[^ ]+]] = getelementptr inbounds i16, i16* %in, i32 -1
+; CHECK: [[LD_IN_MINUS_1:%[^ ]+]] = load i16, i16* [[ADDR_IN_MINUS_1]], align 2
+; CHECK: [[IN_MINUS_1:%[^ ]+]] = sext i16 [[LD_IN_MINUS_1]] to i32
+; CHECK: [[ADDR_B_PLUS_1:%[^ ]+]] = getelementptr inbounds i16, i16* %b, i32 1
+; CHECK: [[LD_B_PLUS_1:%[^ ]+]] = load i16, i16* [[ADDR_B_PLUS_1]], align 2
+; CHECK: [[B_PLUS_1:%[^ ]+]] = sext i16 [[LD_B_PLUS_1]] to i32
+; CHECK: [[MUL0:%[^ ]+]] = mul nsw i32 [[B_PLUS_1]], [[IN_MINUS_1]]
+; CHECK: [[SEXT1:%[^ ]+]] = sext i32 [[MUL0]] to i64
+; CHECK: [[ADD0:%[^ ]+]] = add i64 %sext.0, [[SEXT1]]
+; CHECK: [[ADDR_IN_MINUS_3:%[^ ]+]] = getelementptr inbounds i16, i16* %in, i32 -3
+; CHECK: [[CAST_ADDR_IN_MINUS_3:%[^ ]+]] = bitcast i16* [[ADDR_IN_MINUS_3]] to i32*
+; CHECK: [[IN_MINUS_3:%[^ ]+]] = load i32, i32* [[CAST_ADDR_IN_MINUS_3]], align 2
+; CHECK: [[ADDR_B_PLUS_2:%[^ ]+]] = getelementptr inbounds i16, i16* %b, i32 2
+; CHECK: [[CAST_ADDR_B_PLUS_2:%[^ ]+]] = bitcast i16* [[ADDR_B_PLUS_2]] to i32*
+; CHECK: [[B_PLUS_2:%[^ ]+]] = load i32, i32* [[CAST_ADDR_B_PLUS_2]], align 2
+; CHECK: [[ADDR_IN_MINUS_5:%[^ ]+]] = getelementptr inbounds i16, i16* %in, i32 -5
+; CHECK: [[CAST_ADDR_IN_MINUS_5:%[^ ]+]] = bitcast i16* [[ADDR_IN_MINUS_5]] to i32*
+; CHECK: [[IN_MINUS_5:%[^ ]+]] = load i32, i32* [[CAST_ADDR_IN_MINUS_5]], align 2
+; CHECK: [[ADDR_B_PLUS_4:%[^ ]+]] = getelementptr inbounds i16, i16* %b, i32 4
+; CHECK: [[CAST_ADDR_B_PLUS_4:%[^ ]+]] = bitcast i16* [[ADDR_B_PLUS_4]] to i32*
+; CHECK: [[B_PLUS_4:%[^ ]+]] = load i32, i32* [[CAST_ADDR_B_PLUS_4]], align 2
+; CHECK: [[ACC:%[^ ]+]] = call i64 @llvm.arm.smlaldx(i32 [[IN_MINUS_5]], i32 [[B_PLUS_4]], i64 [[ADD0]])
+; CHECK: [[RES:%[^ ]+]] = call i64 @llvm.arm.smlaldx(i32 [[IN_MINUS_3]], i32 [[B_PLUS_2]], i64 [[ACC]])
+; CHECK: ret i64 [[RES]]
+define i64 @with_64bit_acc(i16* nocapture readonly %in, i16* nocapture readonly %b) {
+entry:
+  %0 = load i16, i16* %in, align 2
+  %conv = sext i16 %0 to i32
+  %1 = load i16, i16* %b, align 2
+  %conv2 = sext i16 %1 to i32
+  %call = tail call i32 @bar(i32 %conv, i32 %conv2)
+  %sext.0 = sext i32 %call to i64
+  %arrayidx3 = getelementptr inbounds i16, i16* %in, i32 -1
+  %2 = load i16, i16* %arrayidx3, align 2
+  %conv4 = sext i16 %2 to i32
+  %arrayidx5 = getelementptr inbounds i16, i16* %b, i32 1
+  %3 = load i16, i16* %arrayidx5, align 2
+  %conv6 = sext i16 %3 to i32
+  %mul = mul nsw i32 %conv6, %conv4
+  %sext.1 = sext i32 %mul to i64
+  %add = add i64 %sext.0, %sext.1
+  %arrayidx7 = getelementptr inbounds i16, i16* %in, i32 -2
+  %4 = load i16, i16* %arrayidx7, align 2
+  %conv8 = sext i16 %4 to i32
+  %arrayidx9 = getelementptr inbounds i16, i16* %b, i32 2
+  %5 = load i16, i16* %arrayidx9, align 2
+  %conv10 = sext i16 %5 to i32
+  %mul11 = mul nsw i32 %conv10, %conv8
+  %sext.2 = sext i32 %mul11 to i64
+  %add12 = add i64 %add, %sext.2
+  %arrayidx13 = getelementptr inbounds i16, i16* %in, i32 -3
+  %6 = load i16, i16* %arrayidx13, align 2
+  %conv14 = sext i16 %6 to i32
+  %arrayidx15 = getelementptr inbounds i16, i16* %b, i32 3
+  %7 = load i16, i16* %arrayidx15, align 2
+  %conv16 = sext i16 %7 to i32
+  %mul17 = mul nsw i32 %conv16, %conv14
+  %sext.3 = sext i32 %mul17 to i64
+  %add18 = add i64 %add12, %sext.3
+  %arrayidx19 = getelementptr inbounds i16, i16* %in, i32 -4
+  %8 = load i16, i16* %arrayidx19, align 2
+  %conv20 = sext i16 %8 to i32
+  %arrayidx21 = getelementptr inbounds i16, i16* %b, i32 4
+  %9 = load i16, i16* %arrayidx21, align 2
+  %conv22 = sext i16 %9 to i32
+  %mul23 = mul nsw i32 %conv22, %conv20
+  %sext.4 = sext i32 %mul23 to i64
+  %add24 = add i64 %add18, %sext.4
+  %arrayidx25 = getelementptr inbounds i16, i16* %in, i32 -5
+  %10 = load i16, i16* %arrayidx25, align 2
+  %conv26 = sext i16 %10 to i32
+  %arrayidx27 = getelementptr inbounds i16, i16* %b, i32 5
+  %11 = load i16, i16* %arrayidx27, align 2
+  %conv28 = sext i16 %11 to i32
+  %mul29 = mul nsw i32 %conv28, %conv26
+  %sext.5 = sext i32 %mul29 to i64
+  %add30 = add i64 %add24, %sext.5
+  ret i64 %add30
+}
+
+; CHECK: with_64bit_add_acc
+; CHECK: [[ADDR_X_PLUS_1:%[^ ]+]] = getelementptr inbounds i16, i16* %px.10756.unr, i32 1
+; CHECK: [[X:%[^ ]+]] = load i16, i16* %px.10756.unr, align 2
+; CHECK: [[SEXT_X:%[^ ]+]] = sext i16 [[X]] to i32
+; CHECK: [[ADDR_Y_MINUS_1:%[^ ]+]] = getelementptr inbounds i16, i16* %py.8757.unr, i32 -1
+; CHECK: [[Y:%[^ ]+]] = load i16, i16* %py.8757.unr, align 2
+; CHECK: [[SEXT_Y:%[^ ]+]] = sext i16 [[Y]] to i32
+; CHECK: [[MUL0:%[^ ]+]] = mul nsw i32 [[SEXT_Y]], [[SEXT_X]]
+; CHECK: [[SEXT_MUL0:%[^ ]+]] = sext i32 [[MUL0]] to i64
+; CHECK: [[ADD_1:%[^ ]+]] = add nsw i64 %sum.3758.unr, [[SEXT_MUL0]]
+; CHECK: [[X_PLUS_2:%[^ ]+]] = getelementptr inbounds i16, i16* %px.10756.unr, i32 2
+; CHECK: [[X_1:%[^ ]+]] = load i16, i16* [[ADDR_X_PLUS_1]], align 2
+; CHECK: [[SEXT_X_1:%[^ ]+]] = sext i16 [[X_1]] to i32
+; CHECK: [[Y_1:%[^ ]+]] = load i16, i16* [[ADDR_Y_MINUS_1]], align 2
+; CHECK: [[SEXT_Y_1:%[^ ]+]] = sext i16 [[Y_1]] to i32
+; CHECK: [[UNPAIRED:%[^ ]+]] = mul nsw i32 [[SEXT_Y_1]], [[SEXT_X_1]]
+; CHECK: [[ADDR_X_PLUS_2:%[^ ]+]] = bitcast i16* [[X_PLUS_2]] to i32*
+; CHECK: [[X_2:%[^ ]+]] = load i32, i32* [[ADDR_X_PLUS_2]], align 2
+; CHECK: [[Y_MINUS_3:%[^ ]+]] = getelementptr inbounds i16, i16* %py.8757.unr, i32 -3
+; CHECK: [[ADDR_Y_MINUS_3:%[^ ]+]] = bitcast i16* [[Y_MINUS_3]] to i32*
+; CHECK: [[Y_3:%[^ ]+]] = load i32, i32* [[ADDR_Y_MINUS_3]], align 2
+; CHECK: [[SEXT:%[^ ]+]] = sext i32 [[UNPAIRED]] to i64
+; CHECK: [[ACC:%[^ ]+]] = add i64 [[SEXT]], [[ADD_1]]
+; CHECK: [[RES:%[^ ]+]] = call i64 @llvm.arm.smlaldx(i32 [[Y_3]], i32 [[X_2]], i64 [[ACC]])
+; CHECK: ret i64 [[RES]]
+define i64 @with_64bit_add_acc(i16* nocapture readonly %px.10756.unr, i16* nocapture readonly %py.8757.unr, i32 %acc) {
+entry:
+  %sum.3758.unr = sext i32 %acc to i64
+  br label %bb.1
+
+bb.1:
+  %incdec.ptr184.epil = getelementptr inbounds i16, i16* %px.10756.unr, i32 1
+  %tmp216 = load i16, i16* %px.10756.unr, align 2
+  %conv185.epil = sext i16 %tmp216 to i32
+  %incdec.ptr186.epil = getelementptr inbounds i16, i16* %py.8757.unr, i32 -1
+  %tmp217 = load i16, i16* %py.8757.unr, align 2
+  %conv187.epil = sext i16 %tmp217 to i32
+  %mul.epil = mul nsw i32 %conv187.epil, %conv185.epil
+  %conv188.epil = sext i32 %mul.epil to i64
+  %add189.epil = add nsw i64 %sum.3758.unr, %conv188.epil
+  %incdec.ptr190.epil = getelementptr inbounds i16, i16* %px.10756.unr, i32 2
+  %tmp218 = load i16, i16* %incdec.ptr184.epil, align 2
+  %conv191.epil = sext i16 %tmp218 to i32
+  %incdec.ptr192.epil = getelementptr inbounds i16, i16* %py.8757.unr, i32 -2
+  %tmp219 = load i16, i16* %incdec.ptr186.epil, align 2
+  %conv193.epil = sext i16 %tmp219 to i32
+  %mul194.epil = mul nsw i32 %conv193.epil, %conv191.epil
+  %conv195.epil = sext i32 %mul194.epil to i64
+  %add196.epil = add nsw i64 %add189.epil, %conv195.epil
+  %incdec.ptr197.epil = getelementptr inbounds i16, i16* %px.10756.unr, i32 3
+  %tmp220 = load i16, i16* %incdec.ptr190.epil, align 2
+  %conv198.epil = sext i16 %tmp220 to i32
+  %incdec.ptr199.epil = getelementptr inbounds i16, i16* %py.8757.unr, i32 -3
+  %tmp221 = load i16, i16* %incdec.ptr192.epil, align 2
+  %conv200.epil = sext i16 %tmp221 to i32
+  %mul201.epil = mul nsw i32 %conv200.epil, %conv198.epil
+  %conv202.epil = sext i32 %mul201.epil to i64
+  %add203.epil = add nsw i64 %add196.epil, %conv202.epil
+  %tmp222 = load i16, i16* %incdec.ptr197.epil, align 2
+  %conv205.epil = sext i16 %tmp222 to i32
+  %tmp223 = load i16, i16* %incdec.ptr199.epil, align 2
+  %conv207.epil = sext i16 %tmp223 to i32
+  %mul208.epil = mul nsw i32 %conv207.epil, %conv205.epil
+  %conv209.epil = sext i32 %mul208.epil to i64
+  %add210.epil = add nsw i64 %add203.epil, %conv209.epil
+  ret i64 %add210.epil
+}
+
 declare dso_local i32 @bar(i32, i32) local_unnamed_addr