[llvm] r348536 - [X86] Directly create ADC/SBB nodes instead of using ADD/SUB with (and SETCC_CARRY, 1)

[Craig Topper via llvm-commits]

Author: ctopper
Date: Thu Dec  6 14:26:59 2018
New Revision: 348536

URL: http://llvm.org/viewvc/llvm-project?rev=348536&view=rev
Log:
[X86] Directly create ADC/SBB nodes instead of using ADD/SUB with (and SETCC_CARRY, 1)

This addresses a FIXME and avoids depending on an isel pattern match I think. I've remove the isel patterns too since he have no lit tests left that cover them. Hopefully that really means they are unused.

I'm trying to decide if we need SETCC_CARRY. This removes one of its usages.

Differential Revision: https://reviews.llvm.org/D55355

Modified:
    llvm/trunk/lib/Target/X86/X86ISelLowering.cpp
    llvm/trunk/lib/Target/X86/X86InstrCompiler.td

Modified: llvm/trunk/lib/Target/X86/X86ISelLowering.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/X86ISelLowering.cpp?rev=348536&r1=348535&r2=348536&view=diff
==============================================================================
--- llvm/trunk/lib/Target/X86/X86ISelLowering.cpp (original)
+++ llvm/trunk/lib/Target/X86/X86ISelLowering.cpp Thu Dec  6 14:26:59 2018
@@ -39995,18 +39995,6 @@ static SDValue combineADC(SDNode *N, Sel
   return SDValue();
 }
 
-/// Materialize "setb reg" as "sbb reg,reg", since it produces an all-ones bit
-/// which is more useful than 0/1 in some cases.
-static SDValue materializeSBB(SDNode *N, SDValue EFLAGS, SelectionDAG &DAG) {
-  SDLoc DL(N);
-  // "Condition code B" is also known as "the carry flag" (CF).
-  SDValue CF = DAG.getConstant(X86::COND_B, DL, MVT::i8);
-  SDValue SBB = DAG.getNode(X86ISD::SETCC_CARRY, DL, MVT::i8, CF, EFLAGS);
-  MVT VT = N->getSimpleValueType(0);
-  assert(VT == MVT::i8 && "Unexpected type for SETCC node");
-  return DAG.getNode(ISD::AND, DL, VT, SBB, DAG.getConstant(1, DL, VT));
-}
-
 /// If this is an add or subtract where one operand is produced by a cmp+setcc,
 /// then try to convert it to an ADC or SBB. This replaces TEST+SET+{ADD/SUB}
 /// with CMP+{ADC, SBB}.
@@ -40077,13 +40065,11 @@ static SDValue combineAddOrSubToADCOrSBB
   }
 
   if (CC == X86::COND_B) {
-    // X + SETB Z --> X + (mask SBB Z, Z)
-    // X - SETB Z --> X - (mask SBB Z, Z)
-    // TODO: Produce ADC/SBB here directly and avoid SETCC_CARRY?
-    SDValue SBB = materializeSBB(Y.getNode(), Y.getOperand(1), DAG);
-    if (SBB.getValueSizeInBits() != VT.getSizeInBits())
-      SBB = DAG.getZExtOrTrunc(SBB, DL, VT);
-    return DAG.getNode(IsSub ? ISD::SUB : ISD::ADD, DL, VT, X, SBB);
+    // X + SETB Z --> adc X, 0
+    // X - SETB Z --> sbb X, 0
+    return DAG.getNode(IsSub ? X86ISD::SBB : X86ISD::ADC, DL,
+                       DAG.getVTList(VT, MVT::i32), X,
+                       DAG.getConstant(0, DL, VT), Y.getOperand(1));
   }
 
   if (CC == X86::COND_A) {
@@ -40101,10 +40087,9 @@ static SDValue combineAddOrSubToADCOrSBB
                                    EFLAGS.getNode()->getVTList(),
                                    EFLAGS.getOperand(1), EFLAGS.getOperand(0));
       SDValue NewEFLAGS = SDValue(NewSub.getNode(), EFLAGS.getResNo());
-      SDValue SBB = materializeSBB(Y.getNode(), NewEFLAGS, DAG);
-      if (SBB.getValueSizeInBits() != VT.getSizeInBits())
-        SBB = DAG.getZExtOrTrunc(SBB, DL, VT);
-      return DAG.getNode(IsSub ? ISD::SUB : ISD::ADD, DL, VT, X, SBB);
+      return DAG.getNode(IsSub ? X86ISD::SBB : X86ISD::ADC, DL,
+                         DAG.getVTList(VT, MVT::i32), X,
+                         DAG.getConstant(0, DL, VT), NewEFLAGS);
     }
   }
 

Modified: llvm/trunk/lib/Target/X86/X86InstrCompiler.td
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/X86InstrCompiler.td?rev=348536&r1=348535&r2=348536&view=diff
==============================================================================
--- llvm/trunk/lib/Target/X86/X86InstrCompiler.td (original)
+++ llvm/trunk/lib/Target/X86/X86InstrCompiler.td Thu Dec  6 14:26:59 2018
@@ -362,30 +362,6 @@ def : Pat<(i64 (sext (i8 (X86setcc_c X86
 def : Pat<(and (i8 (X86setcc_c X86_COND_B, EFLAGS)), 1),
           (SETBr)>;
 
-// (add OP, SETB) -> (adc OP, 0)
-def : Pat<(add (and (i8 (X86setcc_c X86_COND_B, EFLAGS)), 1), GR8:$op),
-          (ADC8ri GR8:$op, 0)>;
-def : Pat<(add (and (i32 (X86setcc_c X86_COND_B, EFLAGS)), 1), GR32:$op),
-          (ADC32ri8 GR32:$op, 0)>;
-def : Pat<(add (and (i64 (X86setcc_c X86_COND_B, EFLAGS)), 1), GR64:$op),
-          (ADC64ri8 GR64:$op, 0)>;
-
-// (sub OP, SETB) -> (sbb OP, 0)
-def : Pat<(sub GR8:$op, (and (i8 (X86setcc_c X86_COND_B, EFLAGS)), 1)),
-          (SBB8ri GR8:$op, 0)>;
-def : Pat<(sub GR32:$op, (and (i32 (X86setcc_c X86_COND_B, EFLAGS)), 1)),
-          (SBB32ri8 GR32:$op, 0)>;
-def : Pat<(sub GR64:$op, (and (i64 (X86setcc_c X86_COND_B, EFLAGS)), 1)),
-          (SBB64ri8 GR64:$op, 0)>;
-
-// (sub OP, SETCC_CARRY) -> (adc OP, 0)
-def : Pat<(sub GR8:$op, (i8 (X86setcc_c X86_COND_B, EFLAGS))),
-          (ADC8ri GR8:$op, 0)>;
-def : Pat<(sub GR32:$op, (i32 (X86setcc_c X86_COND_B, EFLAGS))),
-          (ADC32ri8 GR32:$op, 0)>;
-def : Pat<(sub GR64:$op, (i64 (X86setcc_c X86_COND_B, EFLAGS))),
-          (ADC64ri8 GR64:$op, 0)>;
-
 //===----------------------------------------------------------------------===//
 // String Pseudo Instructions
 //