[DAGCombine] Generalize the case (add (or x, c1), c2) -> (add x, (c1 + c2))

[craig.topper]

llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp

2189–2190

Update the comment.

[lebedev.ri]

llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp

2192

I strongly suspect you need , /* NoOpaque */ true here, else folding can fail.

[RKSimon]

llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp

2194–2196

Probably safer to assume FoldConstantArithmetic can fail:

if (SDValue Add0 = DAG.FoldConstantArithmetic(ISD::ADD, DL, VT, {N1, N0.getOperand(1)}))
  return DAG.getNode(ISD::ADD, DL, VT, N0.getOperand(0), Add0);

[hliao]

Revise the original comment.

[hliao]

Revise again

[lebedev.ri]

lg

llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp

if (N0.getOpcode() == ISD::SIGN_EXTEND && N0.hasOneUse() &&
            (TLI.isOperationLegal(ISD::XOR, X.getValueType()) &&
             TLI.isOperationLegal(ISD::ZERO_EXTEND, VT))) &&
           X.getScalarValueSizeInBits() == 1) {
         SDValue Not = DAG.getNOT(DL, X, X.getValueType());
         return DAG.getNode(ISD::ZERO_EXTEND, DL, VT, Not);
       }
     }
 
-    // Undo the add -> or combine to merge constant offsets from a frame index.
+    // Fold (add (or x, c0), c1) -> (add x, (c0 + c1)) if (or x, c0) is
+    // equivalent to (add x, c0).
     if (N0.getOpcode() == ISD::OR &&
-        isa<FrameIndexSDNode>(N0.getOperand(0)) &&
-        isa<ConstantSDNode>(N0.getOperand(1)) &&
+        isConstantOrConstantVector(N0.getOperand(1), /* NoOpaque */ true) &&
         DAG.haveNoCommonBitsSet(N0.getOperand(0), N0.getOperand(1))) {
-      SDValue Add0 = DAG.getNode(ISD::ADD, DL, VT, N1, N0.getOperand(1));
+      if (SDValue Add0 = DAG.FoldConstantArithmetic(ISD::ADD, DL, VT,
+                                                    {N1, N0.getOperand(1)}))
         return DAG.getNode(ISD::ADD, DL, VT, N0.getOperand(0), Add0);
     }
   }
 
   if (SDValue NewSel = foldBinOpIntoSelect(N))
     return NewSel;
 
   // reassociate add
   if (!reassociationCanBreakAddressingModePattern(ISD::ADD, DL, N0, N1)) {

llvm/test/CodeGen/ARM/va_arg.ll

 ; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
 ; RUN: llc < %s -mtriple=armv7-none-linux-gnueabi -pre-RA-sched=source | FileCheck %s
 ; Test that we correctly align elements when using va_arg
 
 define i64 @test1(i32 %i, ...) nounwind optsize {
 ; CHECK-LABEL: test1:
 ; CHECK:       @ %bb.0: @ %entry
 ; CHECK-NEXT:    .pad #12
 ; CHECK-NEXT:    sub sp, sp, #12
 ; CHECK-NEXT:    .pad #4
 ; CHECK-NEXT:    sub sp, sp, #4
 ; CHECK-NEXT:    add r0, sp, #4
 ; CHECK-NEXT:    stmib sp, {r1, r2, r3}
 ; CHECK-NEXT:    add r0, r0, #7
 ; CHECK-NEXT:    bic r1, r0, #7
-; CHECK-NEXT:    orr r2, r1, #4
-; CHECK-NEXT:    str r2, [sp]
+; CHECK-NEXT:    orr r0, r1, #4
+; CHECK-NEXT:    str r0, [sp]
 ; CHECK-NEXT:    ldr r0, [r1]
-; CHECK-NEXT:    add r2, r2, #4
+; CHECK-NEXT:    add r2, r1, #8
 ; CHECK-NEXT:    str r2, [sp]
 ; CHECK-NEXT:    ldr r1, [r1, #4]
 ; CHECK-NEXT:    add sp, sp, #4
 ; CHECK-NEXT:    add sp, sp, #12
 ; CHECK-NEXT:    bx lr
 entry:
   %g = alloca i8*, align 4
   %g1 = bitcast i8** %g to i8*

llvm/test/CodeGen/Mips/cconv/arguments-varargs.ll

 ; Load the first argument from the variable portion and copy it to the global.
 ; This has used the stack pointer directly rather than the [[VA]] we just set
 ; up.
 ; Big-endian mode for N32/N64 must add an additional 4 to the offset due to byte
 ; order.
 ; O32-DAG:       addiu [[GV:\$[0-9]+]], ${{[0-9]+}}, %lo(dwords)
 ; O32-DAG:       lw [[ARG1:\$[0-9]+]], 0([[VA_TMP2]])
 ; O32-DAG:       sw [[ARG1]], 8([[GV]])
-; O32-DAG:       addiu [[VA3:\$[0-9]+]], [[VA2]], 4
+; O32-DAG:       addiu [[VA3:\$[0-9]+]], [[VA_TMP2]], 8
 ; O32-DAG:       sw [[VA3]], 0([[SP]])
 ; O32-DAG:       lw [[ARG1:\$[0-9]+]], 4([[VA_TMP2]])
 ; O32-DAG:       sw [[ARG1]], 12([[GV]])
 
 ; N32-DAG:       addiu [[GV:\$[0-9]+]], ${{[0-9]+}}, %lo(dwords)
 ; N64-DAG:       daddiu [[GV:\$[0-9]+]], ${{[0-9]+}}, %lo(dwords)
 ; NEW-DAG:       ld [[ARG1:\$[0-9]+]], 0([[VA]])
 ; NEW-DAG:       sd [[ARG1]], 8([[GV]])

 
 ; N64-DAG:       ld [[VA2:\$[0-9]+]], 0([[SP]])
 ; N64-DAG:       daddiu [[VA3:\$[0-9]+]], [[VA2]], 8
 ; N64-DAG:       sd [[VA3]], 0([[SP]])
 
 ; Load the second argument from the variable portion and copy it to the global.
 ; O32-DAG:       lw [[ARG2:\$[0-9]+]], 0([[VA]])
 ; O32-DAG:       sw [[ARG2]], 16([[GV]])
-; O32-DAG:       addiu [[VA3:\$[0-9]+]], [[VA2]], 4
+; O32-DAG:       addiu [[VA3:\$[0-9]+]], [[VA_TMP2]], 8
 ; O32-DAG:       sw [[VA3]], 0([[SP]])
 ; O32-DAG:       lw [[ARG2:\$[0-9]+]], 4([[VA_TMP2]])
 ; O32-DAG:       sw [[ARG2]], 20([[GV]])
 
 ; NEW-DAG:       ld [[ARG2:\$[0-9]+]], 0([[VA2]])
 ; NEW-DAG:       sd [[ARG2]], 16([[GV]])
 
   %ap = alloca i8*, align 8

 ; Load the first argument from the variable portion and copy it to the global.
 ; This has used the stack pointer directly rather than the [[VA]] we just set
 ; up.
 ; Big-endian mode for N32/N64 must add an additional 4 to the offset due to byte
 ; order.
 ; O32-DAG:       addiu [[GV:\$[0-9]+]], ${{[0-9]+}}, %lo(dwords)
 ; O32-DAG:       lw [[ARG1:\$[0-9]+]], 0([[VA_TMP2]])
 ; O32-DAG:       sw [[ARG1]], 8([[GV]])
-; O32-DAG:       addiu [[VA3:\$[0-9]+]], [[VA2]], 4
+; O32-DAG:       addiu [[VA3:\$[0-9]+]], [[VA_TMP2]], 8
 ; O32-DAG:       sw [[VA3]], 0([[SP]])
 ; O32-DAG:       lw [[ARG1:\$[0-9]+]], 4([[VA_TMP2]])
 ; O32-DAG:       sw [[ARG1]], 12([[GV]])
 
 ; N32-DAG:       addiu [[GV:\$[0-9]+]], ${{[0-9]+}}, %lo(dwords)
 ; N64-DAG:       daddiu [[GV:\$[0-9]+]], ${{[0-9]+}}, %lo(dwords)
 ; NEW-DAG:       ld [[ARG1:\$[0-9]+]], 0([[VA]])
 ; NEW-DAG:       sd [[ARG1]], 8([[GV]])

 
 ; N64-DAG:       ld [[VA2:\$[0-9]+]], 0([[SP]])
 ; N64-DAG:       daddiu [[VA3:\$[0-9]+]], [[VA2]], 8
 ; N64-DAG:       sd [[VA3]], 0([[SP]])
 
 ; Load the second argument from the variable portion and copy it to the global.
 ; O32-DAG:       lw [[ARG2:\$[0-9]+]], 0([[VA]])
 ; O32-DAG:       sw [[ARG2]], 16([[GV]])
-; O32-DAG:       addiu [[VA3:\$[0-9]+]], [[VA2]], 4
-; O32-DAG:       sw [[VA2]], 0([[SP]])
+; O32-DAG:       addiu [[VA3:\$[0-9]+]], [[VA_TMP2]], 8
+; O32-DAG:       sw [[VA3]], 0([[SP]])
 ; O32-DAG:       lw [[ARG2:\$[0-9]+]], 4([[VA_TMP2]])
 ; O32-DAG:       sw [[ARG2]], 20([[GV]])
 
 ; NEW-DAG:       ld [[ARG2:\$[0-9]+]], 0([[VA2]])
 ; NEW-DAG:       sd [[ARG2]], 16([[GV]])
 
   %ap = alloca i8*, align 8
   %ap2 = bitcast i8** %ap to i8*

 ; Load the first argument from the variable portion and copy it to the global.
 ; This has used the stack pointer directly rather than the [[VA]] we just set
 ; up.
 ; Big-endian mode for N32/N64 must add an additional 4 to the offset due to byte
 ; order.
 ; O32-DAG:       addiu [[GV:\$[0-9]+]], ${{[0-9]+}}, %lo(dwords)
 ; O32-DAG:       lw [[ARG1:\$[0-9]+]], 0([[VA]])
 ; O32-DAG:       sw [[ARG1]], 8([[GV]])
-; O32-DAG:       addiu [[VA3:\$[0-9]+]], [[VA2]], 4
+; O32-DAG:       addiu [[VA3:\$[0-9]+]], [[VA_TMP2]], 8
 ; O32-DAG:       sw [[VA3]], 0([[SP]])
 ; O32-DAG:       lw [[ARG1:\$[0-9]+]], 4([[VA_TMP2]])
 ; O32-DAG:       sw [[ARG1]], 12([[GV]])
 
 ; N32-DAG:       addiu [[GV:\$[0-9]+]], ${{[0-9]+}}, %lo(dwords)
 ; N64-DAG:       daddiu [[GV:\$[0-9]+]], ${{[0-9]+}}, %lo(dwords)
 ; NEW-DAG:       ld [[ARG1:\$[0-9]+]], 0([[VA]])
 ; NEW-DAG:       sd [[ARG1]], 8([[GV]])

 ; N32-DAG:       sw [[VA3]], 0([[SP]])
 
 ; N64-DAG:       ld [[VA2:\$[0-9]+]], 0([[SP]])
 ; N64-DAG:       daddiu [[VA3:\$[0-9]+]], [[VA2]], 8
 ; N64-DAG:       sd [[VA3]], 0([[SP]])
 
 ; Load the second argument from the variable portion and copy it to the global.
 ; O32-DAG:       lw [[ARG2:\$[0-9]+]], 0([[VA]])
-; O32-DAG:       sw [[ARG2]], 16([[GV]])
-; O32-DAG:       addiu [[VA3:\$[0-9]+]], [[VA2]], 4
+; O32-DAG:       addiu [[VA3:\$[0-9]+]], [[VA_TMP2]], 8
 ; O32-DAG:       sw [[VA3]], 0([[SP]])
-; O32-DAG:       lw [[ARG2:\$[0-9]+]], 4([[VA_TMP2]])
-; O32-DAG:       sw [[ARG2]], 20([[GV]])
+; O32-DAG:       lw [[ARG3:\$[0-9]+]], 4([[VA_TMP2]])
+; O32-DAG:       sw [[ARG3]], 20([[GV]])
+; O32-DAG:       sw [[ARG2]], 16([[GV]])
 
 ; NEW-DAG:       ld [[ARG2:\$[0-9]+]], 0([[VA2]])
 ; NEW-DAG:       sd [[ARG2]], 16([[GV]])
 
   %ap = alloca i8*, align 8
   %ap2 = bitcast i8** %ap to i8*
   call void @llvm.va_start(i8* %ap2)
 

llvm/test/CodeGen/RISCV/vararg.ll

 ; ILP32-ILP32F-FPELIM-NEXT:    sw a7, 44(sp)
 ; ILP32-ILP32F-FPELIM-NEXT:    sw a6, 40(sp)
 ; ILP32-ILP32F-FPELIM-NEXT:    sw a5, 36(sp)
 ; ILP32-ILP32F-FPELIM-NEXT:    sw a4, 32(sp)
 ; ILP32-ILP32F-FPELIM-NEXT:    sw a3, 28(sp)
 ; ILP32-ILP32F-FPELIM-NEXT:    sw a2, 24(sp)
 ; ILP32-ILP32F-FPELIM-NEXT:    sw a1, 20(sp)
 ; ILP32-ILP32F-FPELIM-NEXT:    addi a0, sp, 27
-; ILP32-ILP32F-FPELIM-NEXT:    andi a0, a0, -8
-; ILP32-ILP32F-FPELIM-NEXT:    ori a1, a0, 4
-; ILP32-ILP32F-FPELIM-NEXT:    sw a1, 12(sp)
-; ILP32-ILP32F-FPELIM-NEXT:    lw a0, 0(a0)
-; ILP32-ILP32F-FPELIM-NEXT:    addi a2, a1, 4
+; ILP32-ILP32F-FPELIM-NEXT:    andi a1, a0, -8
+; ILP32-ILP32F-FPELIM-NEXT:    ori a2, a1, 4
 ; ILP32-ILP32F-FPELIM-NEXT:    sw a2, 12(sp)
-; ILP32-ILP32F-FPELIM-NEXT:    lw a1, 0(a1)
+; ILP32-ILP32F-FPELIM-NEXT:    lw a0, 0(a1)
+; ILP32-ILP32F-FPELIM-NEXT:    addi a1, a1, 8
+; ILP32-ILP32F-FPELIM-NEXT:    sw a1, 12(sp)
+; ILP32-ILP32F-FPELIM-NEXT:    lw a1, 0(a2)
 ; ILP32-ILP32F-FPELIM-NEXT:    addi sp, sp, 48
 ; ILP32-ILP32F-FPELIM-NEXT:    ret
 ;
 ; ILP32-ILP32F-WITHFP-LABEL: va2_va_arg:
 ; ILP32-ILP32F-WITHFP:       # %bb.0:
 ; ILP32-ILP32F-WITHFP-NEXT:    addi sp, sp, -48
 ; ILP32-ILP32F-WITHFP-NEXT:    sw ra, 12(sp)
 ; ILP32-ILP32F-WITHFP-NEXT:    sw s0, 8(sp)
 ; ILP32-ILP32F-WITHFP-NEXT:    addi s0, sp, 16
 ; ILP32-ILP32F-WITHFP-NEXT:    sw a7, 28(s0)
 ; ILP32-ILP32F-WITHFP-NEXT:    sw a6, 24(s0)
 ; ILP32-ILP32F-WITHFP-NEXT:    sw a5, 20(s0)
 ; ILP32-ILP32F-WITHFP-NEXT:    sw a4, 16(s0)
 ; ILP32-ILP32F-WITHFP-NEXT:    sw a3, 12(s0)
 ; ILP32-ILP32F-WITHFP-NEXT:    sw a2, 8(s0)
 ; ILP32-ILP32F-WITHFP-NEXT:    sw a1, 4(s0)
 ; ILP32-ILP32F-WITHFP-NEXT:    addi a0, s0, 11
-; ILP32-ILP32F-WITHFP-NEXT:    andi a0, a0, -8
-; ILP32-ILP32F-WITHFP-NEXT:    ori a1, a0, 4
-; ILP32-ILP32F-WITHFP-NEXT:    sw a1, -12(s0)
-; ILP32-ILP32F-WITHFP-NEXT:    lw a0, 0(a0)
-; ILP32-ILP32F-WITHFP-NEXT:    addi a2, a1, 4
+; ILP32-ILP32F-WITHFP-NEXT:    andi a1, a0, -8
+; ILP32-ILP32F-WITHFP-NEXT:    ori a2, a1, 4
 ; ILP32-ILP32F-WITHFP-NEXT:    sw a2, -12(s0)
-; ILP32-ILP32F-WITHFP-NEXT:    lw a1, 0(a1)
+; ILP32-ILP32F-WITHFP-NEXT:    lw a0, 0(a1)
+; ILP32-ILP32F-WITHFP-NEXT:    addi a1, a1, 8
+; ILP32-ILP32F-WITHFP-NEXT:    sw a1, -12(s0)
+; ILP32-ILP32F-WITHFP-NEXT:    lw a1, 0(a2)
 ; ILP32-ILP32F-WITHFP-NEXT:    lw s0, 8(sp)
 ; ILP32-ILP32F-WITHFP-NEXT:    lw ra, 12(sp)
 ; ILP32-ILP32F-WITHFP-NEXT:    addi sp, sp, 48
 ; ILP32-ILP32F-WITHFP-NEXT:    ret
 ;
 ; RV32D-ILP32-ILP32F-ILP32D-FPELIM-LABEL: va2_va_arg:
 ; RV32D-ILP32-ILP32F-ILP32D-FPELIM:       # %bb.0:
 ; RV32D-ILP32-ILP32F-ILP32D-FPELIM-NEXT:    addi sp, sp, -48

 ; ILP32-ILP32F-FPELIM-NEXT:    sw a6, 24(sp)
 ; ILP32-ILP32F-FPELIM-NEXT:    sw a5, 20(sp)
 ; ILP32-ILP32F-FPELIM-NEXT:    sw a4, 16(sp)
 ; ILP32-ILP32F-FPELIM-NEXT:    sw a3, 12(sp)
 ; ILP32-ILP32F-FPELIM-NEXT:    addi a0, sp, 19
 ; ILP32-ILP32F-FPELIM-NEXT:    andi a0, a0, -8
 ; ILP32-ILP32F-FPELIM-NEXT:    ori a3, a0, 4
 ; ILP32-ILP32F-FPELIM-NEXT:    sw a3, 4(sp)
-; ILP32-ILP32F-FPELIM-NEXT:    lw a0, 0(a0)
-; ILP32-ILP32F-FPELIM-NEXT:    addi a4, a3, 4
-; ILP32-ILP32F-FPELIM-NEXT:    sw a4, 4(sp)
+; ILP32-ILP32F-FPELIM-NEXT:    lw a4, 0(a0)
+; ILP32-ILP32F-FPELIM-NEXT:    addi a0, a0, 8
+; ILP32-ILP32F-FPELIM-NEXT:    sw a0, 4(sp)
 ; ILP32-ILP32F-FPELIM-NEXT:    lw a3, 0(a3)
-; ILP32-ILP32F-FPELIM-NEXT:    add a0, a1, a0
+; ILP32-ILP32F-FPELIM-NEXT:    add a0, a1, a4
 ; ILP32-ILP32F-FPELIM-NEXT:    sltu a1, a0, a1
 ; ILP32-ILP32F-FPELIM-NEXT:    add a2, a2, a3
 ; ILP32-ILP32F-FPELIM-NEXT:    add a1, a2, a1
 ; ILP32-ILP32F-FPELIM-NEXT:    addi sp, sp, 32
 ; ILP32-ILP32F-FPELIM-NEXT:    ret
 ;
 ; ILP32-ILP32F-WITHFP-LABEL: va3_va_arg:
 ; ILP32-ILP32F-WITHFP:       # %bb.0:
 ; ILP32-ILP32F-WITHFP-NEXT:    addi sp, sp, -48
 ; ILP32-ILP32F-WITHFP-NEXT:    sw ra, 20(sp)
 ; ILP32-ILP32F-WITHFP-NEXT:    sw s0, 16(sp)
 ; ILP32-ILP32F-WITHFP-NEXT:    addi s0, sp, 24
 ; ILP32-ILP32F-WITHFP-NEXT:    sw a7, 20(s0)
 ; ILP32-ILP32F-WITHFP-NEXT:    sw a6, 16(s0)
 ; ILP32-ILP32F-WITHFP-NEXT:    sw a5, 12(s0)
 ; ILP32-ILP32F-WITHFP-NEXT:    sw a4, 8(s0)
 ; ILP32-ILP32F-WITHFP-NEXT:    sw a3, 4(s0)
 ; ILP32-ILP32F-WITHFP-NEXT:    addi a0, s0, 11
 ; ILP32-ILP32F-WITHFP-NEXT:    andi a0, a0, -8
 ; ILP32-ILP32F-WITHFP-NEXT:    ori a3, a0, 4
 ; ILP32-ILP32F-WITHFP-NEXT:    sw a3, -12(s0)
-; ILP32-ILP32F-WITHFP-NEXT:    lw a0, 0(a0)
-; ILP32-ILP32F-WITHFP-NEXT:    addi a4, a3, 4
-; ILP32-ILP32F-WITHFP-NEXT:    sw a4, -12(s0)
+; ILP32-ILP32F-WITHFP-NEXT:    lw a4, 0(a0)
+; ILP32-ILP32F-WITHFP-NEXT:    addi a0, a0, 8
+; ILP32-ILP32F-WITHFP-NEXT:    sw a0, -12(s0)
 ; ILP32-ILP32F-WITHFP-NEXT:    lw a3, 0(a3)
-; ILP32-ILP32F-WITHFP-NEXT:    add a0, a1, a0
+; ILP32-ILP32F-WITHFP-NEXT:    add a0, a1, a4
 ; ILP32-ILP32F-WITHFP-NEXT:    sltu a1, a0, a1
 ; ILP32-ILP32F-WITHFP-NEXT:    add a2, a2, a3
 ; ILP32-ILP32F-WITHFP-NEXT:    add a1, a2, a1
 ; ILP32-ILP32F-WITHFP-NEXT:    lw s0, 16(sp)
 ; ILP32-ILP32F-WITHFP-NEXT:    lw ra, 20(sp)
 ; ILP32-ILP32F-WITHFP-NEXT:    addi sp, sp, 48
 ; ILP32-ILP32F-WITHFP-NEXT:    ret
 ;