[DA] Remove special handling for SCEVAddExpr in GCD MIV (llvm#169927)

In `gcdMIVtest`, there is logic that assumes the addition(s) of
`SCEVAddExpr` don't overflow without any checks. Adding overflow checks
would be fine, but this part appeart to be less useful. So this patch
removes it.

Fix one of the tests added in llvm#169926.

Author: kasuga-fj

llvm/lib/Analysis/DependenceAnalysis.cpp

@@ -2587,30 +2587,12 @@ bool DependenceInfo::gcdMIVtest(const SCEV *Src, const SCEV *Dst,
     return false;
   LLVM_DEBUG(dbgs() << "    Delta = " << *Delta << "\n");
   const SCEVConstant *Constant = dyn_cast<SCEVConstant>(Delta);
-  if (const SCEVAddExpr *Sum = dyn_cast<SCEVAddExpr>(Delta)) {
-    // If Delta is a sum of products, we may be able to make further progress.
-    for (const SCEV *Operand : Sum->operands()) {
-      if (isa<SCEVConstant>(Operand)) {
-        assert(!Constant && "Surprised to find multiple constants");
-        Constant = cast<SCEVConstant>(Operand);
-      } else if (const SCEVMulExpr *Product = dyn_cast<SCEVMulExpr>(Operand)) {
-        // Search for constant operand to participate in GCD;
-        // If none found; return false.
-        std::optional<APInt> ConstOp = getConstanCoefficient(Product);
-        if (!ConstOp)
-          return false;
-        ExtraGCD = APIntOps::GreatestCommonDivisor(ExtraGCD, ConstOp->abs());
-      } else
-        return false;
-    }
-  }
   if (!Constant)
     return false;
   APInt ConstDelta = cast<SCEVConstant>(Constant)->getAPInt();
   LLVM_DEBUG(dbgs() << "    ConstDelta = " << ConstDelta << "\n");
   if (ConstDelta == 0)
     return false;
-  RunningGCD = APIntOps::GreatestCommonDivisor(RunningGCD, ExtraGCD);
   LLVM_DEBUG(dbgs() << "    RunningGCD = " << RunningGCD << "\n");
   APInt Remainder = ConstDelta.srem(RunningGCD);
   if (Remainder != 0) {

llvm/test/Analysis/DependenceAnalysis/gcd-miv-overflow.ll

@@ -127,9 +127,8 @@ exit:
 ;   A[-3*i - 3*m - INT64_MAX] = 1;
 ; }
 ;
-; FIXME: DependenceAnalysis currently detects no dependency between the two
-; stores, but it may exist. For example, consider `m = 1`. Then,
-; `-3*m - INT64_MAX` is `INT64_MAX - 1`. So `-3*i - 3*m - INT64_MAX` is
+; Dependency may exist between the two stores. For example, consider `m = 1`.
+; Then, `-3*m - INT64_MAX` is `INT64_MAX - 1`. So `-3*i - 3*m - INT64_MAX` is
 ; effectively `-3*i + (INT64_MAX - 1)`. Thus, accesses will be as follows:
 ;
 ;  memory access             | i == 1           | i == max_i - 1
@@ -143,15 +142,15 @@ define void @gcdmiv_const_ovfl(ptr %A, i64 %m) {
 ; CHECK-ALL-NEXT:  Src: store i8 0, ptr %gep.0, align 1 --> Dst: store i8 0, ptr %gep.0, align 1
 ; CHECK-ALL-NEXT:    da analyze - none!
 ; CHECK-ALL-NEXT:  Src: store i8 0, ptr %gep.0, align 1 --> Dst: store i8 1, ptr %gep.1, align 1
-; CHECK-ALL-NEXT:    da analyze - none!
+; CHECK-ALL-NEXT:    da analyze - output [*|<]!
 ; CHECK-ALL-NEXT:  Src: store i8 1, ptr %gep.1, align 1 --> Dst: store i8 1, ptr %gep.1, align 1
 ; CHECK-ALL-NEXT:    da analyze - none!
 ;
 ; CHECK-GCD-MIV-LABEL: 'gcdmiv_const_ovfl'
 ; CHECK-GCD-MIV-NEXT:  Src: store i8 0, ptr %gep.0, align 1 --> Dst: store i8 0, ptr %gep.0, align 1
 ; CHECK-GCD-MIV-NEXT:    da analyze - consistent output [*]!
 ; CHECK-GCD-MIV-NEXT:  Src: store i8 0, ptr %gep.0, align 1 --> Dst: store i8 1, ptr %gep.1, align 1
-; CHECK-GCD-MIV-NEXT:    da analyze - none!
+; CHECK-GCD-MIV-NEXT:    da analyze - consistent output [*|<]!
 ; CHECK-GCD-MIV-NEXT:  Src: store i8 1, ptr %gep.1, align 1 --> Dst: store i8 1, ptr %gep.1, align 1
 ; CHECK-GCD-MIV-NEXT:    da analyze - consistent output [*]!
 ;