[CodeGenPrepare][RISCV] Correct the MathUsed flag for shouldFormOverf…

…lowOp

For add, if we match the constant edge case the add isn't used by
the compare so we shouldn't check for 2 users.

For sub, the compare is not a user of the sub so the math is
used if the sub has any users.

This regresses RISC-V which I will work on other patches for.

Reviewed By: RKSimon

Differential Revision: https://reviews.llvm.org/D146786

llvm/lib/CodeGen/CodeGenPrepare.cpp

@@ -1579,6 +1579,7 @@ static bool matchUAddWithOverflowConstantEdgeCases(CmpInst *Cmp,
 /// intrinsic. Return true if any changes were made.
 bool CodeGenPrepare::combineToUAddWithOverflow(CmpInst *Cmp,
                                                ModifyDT &ModifiedDT) {
+  bool EdgeCase = false;
   Value *A, *B;
   BinaryOperator *Add;
   if (!match(Cmp, m_UAddWithOverflow(m_Value(A), m_Value(B), m_BinOp(Add)))) {
@@ -1587,11 +1588,12 @@ bool CodeGenPrepare::combineToUAddWithOverflow(CmpInst *Cmp,
     // Set A and B in case we match matchUAddWithOverflowConstantEdgeCases.
     A = Add->getOperand(0);
     B = Add->getOperand(1);
+    EdgeCase = true;
   }
 
   if (!TLI->shouldFormOverflowOp(ISD::UADDO,
                                  TLI->getValueType(*DL, Add->getType()),
-                                 Add->hasNUsesOrMore(2)))
+                                 Add->hasNUsesOrMore(EdgeCase ? 1 : 2)))
     return false;
 
   // We don't want to move around uses of condition values this late, so we
@@ -1660,7 +1662,7 @@ bool CodeGenPrepare::combineToUSubWithOverflow(CmpInst *Cmp,
 
   if (!TLI->shouldFormOverflowOp(ISD::USUBO,
                                  TLI->getValueType(*DL, Sub->getType()),
-                                 Sub->hasNUsesOrMore(2)))
+                                 Sub->hasNUsesOrMore(1)))
     return false;
 
   if (!replaceMathCmpWithIntrinsic(Sub, Sub->getOperand(0), Sub->getOperand(1),

llvm/test/CodeGen/RISCV/overflow-intrinsics.ll

@@ -612,13 +612,12 @@ define i1 @uaddo_i64_increment_alt(i64 %x, ptr %p) {
 ; RV32-LABEL: uaddo_i64_increment_alt:
 ; RV32:       # %bb.0:
 ; RV32-NEXT:    addi a3, a0, 1
-; RV32-NEXT:    seqz a4, a3
-; RV32-NEXT:    add a4, a1, a4
-; RV32-NEXT:    sw a3, 0(a2)
-; RV32-NEXT:    and a0, a0, a1
-; RV32-NEXT:    addi a0, a0, 1
+; RV32-NEXT:    seqz a0, a3
+; RV32-NEXT:    add a1, a1, a0
+; RV32-NEXT:    or a0, a3, a1
 ; RV32-NEXT:    seqz a0, a0
-; RV32-NEXT:    sw a4, 4(a2)
+; RV32-NEXT:    sw a3, 0(a2)
+; RV32-NEXT:    sw a1, 4(a2)
 ; RV32-NEXT:    ret
 ;
 ; RV64-LABEL: uaddo_i64_increment_alt:
@@ -638,15 +637,13 @@ define i1 @uaddo_i64_increment_alt(i64 %x, ptr %p) {
 define i1 @uaddo_i64_increment_alt_dom(i64 %x, ptr %p) {
 ; RV32-LABEL: uaddo_i64_increment_alt_dom:
 ; RV32:       # %bb.0:
-; RV32-NEXT:    and a3, a0, a1
-; RV32-NEXT:    addi a3, a3, 1
-; RV32-NEXT:    seqz a3, a3
-; RV32-NEXT:    addi a0, a0, 1
-; RV32-NEXT:    seqz a4, a0
-; RV32-NEXT:    add a1, a1, a4
-; RV32-NEXT:    sw a0, 0(a2)
+; RV32-NEXT:    addi a3, a0, 1
+; RV32-NEXT:    seqz a0, a3
+; RV32-NEXT:    add a1, a1, a0
+; RV32-NEXT:    or a0, a3, a1
+; RV32-NEXT:    seqz a0, a0
+; RV32-NEXT:    sw a3, 0(a2)
 ; RV32-NEXT:    sw a1, 4(a2)
-; RV32-NEXT:    mv a0, a3
 ; RV32-NEXT:    ret
 ;
 ; RV64-LABEL: uaddo_i64_increment_alt_dom:
@@ -666,19 +663,24 @@ define i1 @uaddo_i64_increment_alt_dom(i64 %x, ptr %p) {
 define i1 @uaddo_i64_decrement_alt(i64 %x, ptr %p) {
 ; RV32-LABEL: uaddo_i64_decrement_alt:
 ; RV32:       # %bb.0:
-; RV32-NEXT:    seqz a3, a0
-; RV32-NEXT:    sub a3, a1, a3
-; RV32-NEXT:    addi a4, a0, -1
-; RV32-NEXT:    sw a4, 0(a2)
-; RV32-NEXT:    or a0, a0, a1
-; RV32-NEXT:    snez a0, a0
-; RV32-NEXT:    sw a3, 4(a2)
+; RV32-NEXT:    addi a3, a0, -1
+; RV32-NEXT:    seqz a4, a0
+; RV32-NEXT:    sub a4, a1, a4
+; RV32-NEXT:    bnez a0, .LBB18_2
+; RV32-NEXT:  # %bb.1:
+; RV32-NEXT:    sltu a0, a4, a1
+; RV32-NEXT:    j .LBB18_3
+; RV32-NEXT:  .LBB18_2:
+; RV32-NEXT:    sltu a0, a3, a0
+; RV32-NEXT:  .LBB18_3:
+; RV32-NEXT:    sw a3, 0(a2)
+; RV32-NEXT:    sw a4, 4(a2)
 ; RV32-NEXT:    ret
 ;
 ; RV64-LABEL: uaddo_i64_decrement_alt:
 ; RV64:       # %bb.0:
 ; RV64-NEXT:    addi a2, a0, -1
-; RV64-NEXT:    snez a0, a0
+; RV64-NEXT:    sltu a0, a2, a0
 ; RV64-NEXT:    sd a2, 0(a1)
 ; RV64-NEXT:    ret
   %a = add i64 %x, -1
@@ -692,22 +694,25 @@ define i1 @uaddo_i64_decrement_alt(i64 %x, ptr %p) {
 define i1 @uaddo_i64_decrement_alt_dom(i64 %x, ptr %p) {
 ; RV32-LABEL: uaddo_i64_decrement_alt_dom:
 ; RV32:       # %bb.0:
-; RV32-NEXT:    or a3, a0, a1
-; RV32-NEXT:    snez a3, a3
+; RV32-NEXT:    addi a3, a0, -1
 ; RV32-NEXT:    seqz a4, a0
-; RV32-NEXT:    sub a1, a1, a4
-; RV32-NEXT:    addi a0, a0, -1
-; RV32-NEXT:    sw a0, 0(a2)
-; RV32-NEXT:    sw a1, 4(a2)
-; RV32-NEXT:    mv a0, a3
+; RV32-NEXT:    sub a4, a1, a4
+; RV32-NEXT:    bnez a0, .LBB19_2
+; RV32-NEXT:  # %bb.1:
+; RV32-NEXT:    sltu a0, a4, a1
+; RV32-NEXT:    j .LBB19_3
+; RV32-NEXT:  .LBB19_2:
+; RV32-NEXT:    sltu a0, a3, a0
+; RV32-NEXT:  .LBB19_3:
+; RV32-NEXT:    sw a3, 0(a2)
+; RV32-NEXT:    sw a4, 4(a2)
 ; RV32-NEXT:    ret
 ;
 ; RV64-LABEL: uaddo_i64_decrement_alt_dom:
 ; RV64:       # %bb.0:
-; RV64-NEXT:    snez a2, a0
-; RV64-NEXT:    addi a0, a0, -1
-; RV64-NEXT:    sd a0, 0(a1)
-; RV64-NEXT:    mv a0, a2
+; RV64-NEXT:    addi a2, a0, -1
+; RV64-NEXT:    sltu a0, a2, a0
+; RV64-NEXT:    sd a2, 0(a1)
 ; RV64-NEXT:    ret
   %ov = icmp ne i64 %x, 0
   %a = add i64 %x, -1