[llvm] r294394 - [DAGCombiner] Push truncate through adde when the carry isn't used.

[Amaury Sechet via llvm-commits]

Author: deadalnix
Date: Tue Feb  7 18:32:36 2017
New Revision: 294394

URL: http://llvm.org/viewvc/llvm-project?rev=294394&view=rev
Log:
[DAGCombiner] Push truncate through adde when the carry isn't used.

Summary: As per title.

Reviewers: mkuper, spatel, bkramer, RKSimon, zvi

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D29528

Modified:
    llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
    llvm/trunk/test/CodeGen/X86/adde-carry.ll
    llvm/trunk/test/CodeGen/X86/known-bits.ll

Modified: llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp?rev=294394&r1=294393&r2=294394&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp Tue Feb  7 18:32:36 2017
@@ -7866,6 +7866,18 @@ SDValue DAGCombiner::visitTRUNCATE(SDNod
       SimplifyDemandedBits(SDValue(N, 0)))
     return SDValue(N, 0);
 
+  // (trunc adde(X, Y, Carry)) -> (adde trunc(X), trunc(Y), Carry)
+  // When the adde's carry is not used.
+  if (N0.getOpcode() == ISD::ADDE && N0.hasOneUse() &&
+      !N0.getNode()->hasAnyUseOfValue(1) &&
+      (!LegalOperations || TLI.isOperationLegal(ISD::ADDE, VT))) {
+    SDLoc SL(N);
+    auto X = DAG.getNode(ISD::TRUNCATE, SL, VT, N0.getOperand(0));
+    auto Y = DAG.getNode(ISD::TRUNCATE, SL, VT, N0.getOperand(1));
+    return DAG.getNode(ISD::ADDE, SL, DAG.getVTList(VT, MVT::Glue),
+                       X, Y, N0.getOperand(2));
+  }
+
   return SDValue();
 }
 

Modified: llvm/trunk/test/CodeGen/X86/adde-carry.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/adde-carry.ll?rev=294394&r1=294393&r2=294394&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/X86/adde-carry.ll (original)
+++ llvm/trunk/test/CodeGen/X86/adde-carry.ll Tue Feb  7 18:32:36 2017
@@ -28,8 +28,7 @@ define void @b(i32* nocapture %r, i64 %a
 ; CHECK-LABEL: b:
 ; CHECK:       # BB#0: # %entry
 ; CHECK-NEXT:    addq %rdx, %rsi
-; CHECK-NEXT:    sbbq %rax, %rax
-; CHECK-NEXT:    subl %eax, %ecx
+; CHECK-NEXT:    adcl $0, %ecx
 ; CHECK-NEXT:    movl %ecx, (%rdi)
 ; CHECK-NEXT:    retq
 entry:
@@ -48,8 +47,7 @@ define void @c(i16* nocapture %r, i64 %a
 ; CHECK-LABEL: c:
 ; CHECK:       # BB#0: # %entry
 ; CHECK-NEXT:    addq %rdx, %rsi
-; CHECK-NEXT:    sbbq %rax, %rax
-; CHECK-NEXT:    subl %eax, %ecx
+; CHECK-NEXT:    adcl $0, %ecx
 ; CHECK-NEXT:    movw %cx, (%rdi)
 ; CHECK-NEXT:    retq
 entry:
@@ -68,8 +66,7 @@ define void @d(i8* nocapture %r, i64 %a,
 ; CHECK-LABEL: d:
 ; CHECK:       # BB#0: # %entry
 ; CHECK-NEXT:    addq %rdx, %rsi
-; CHECK-NEXT:    sbbq %rax, %rax
-; CHECK-NEXT:    subl %eax, %ecx
+; CHECK-NEXT:    adcl $0, %ecx
 ; CHECK-NEXT:    movb %cl, (%rdi)
 ; CHECK-NEXT:    retq
 entry:
@@ -165,8 +162,8 @@ define void @muladd(%accumulator* nocapt
 ; CHECK-NEXT:    adcq $0, %rdx
 ; CHECK-NEXT:    movq %rax, (%rdi)
 ; CHECK-NEXT:    addq 8(%rdi), %rdx
-; CHECK-NEXT:    sbbq %rax, %rax
 ; CHECK-NEXT:    movq %rdx, 8(%rdi)
+; CHECK-NEXT:    sbbl %eax, %eax
 ; CHECK-NEXT:    subl %eax, 16(%rdi)
 ; CHECK-NEXT:    retq
 entry:

Modified: llvm/trunk/test/CodeGen/X86/known-bits.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/known-bits.ll?rev=294394&r1=294393&r2=294394&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/X86/known-bits.ll (original)
+++ llvm/trunk/test/CodeGen/X86/known-bits.ll Tue Feb  7 18:32:36 2017
@@ -151,8 +151,7 @@ define i128 @knownbits_mask_addc_shl(i64
 ; X64-NEXT:    andq $-1024, %rdi # imm = 0xFC00
 ; X64-NEXT:    andq $-1024, %rsi # imm = 0xFC00
 ; X64-NEXT:    addq %rdi, %rsi
-; X64-NEXT:    sbbq %rax, %rax
-; X64-NEXT:    subl %eax, %edx
+; X64-NEXT:    adcl $0, %edx
 ; X64-NEXT:    shldq $54, %rsi, %rdx
 ; X64-NEXT:    xorl %eax, %eax
 ; X64-NEXT:    retq