[DA] Remove special handling for SCEVAddExpr in GCD MIV

[kasuga-fj]

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 #169926.

[kasuga-fj]

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• [DA] Remove special handling for SCEVAddExpr in GCD MIV #169927 👈 (View in Graphite)
• [DA] Add tests for GCD MIV misses dependency due to overflow (NFC) #169926 : 1 other dependent PR (#169928 )
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[llvmbot]

@llvm/pr-subscribers-llvm-analysis

Author: Ryotaro Kasuga (kasuga-fj)

Changes

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 #169926.

---

Full diff: https://github.com/llvm/llvm-project/pull/169927.diff

2 Files Affected:

• (modified) llvm/lib/Analysis/DependenceAnalysis.cpp (-17)
• (modified) llvm/test/Analysis/DependenceAnalysis/gcd-miv-overflow.ll (+4-5)

diff --git a/llvm/lib/Analysis/DependenceAnalysis.cpp b/llvm/lib/Analysis/DependenceAnalysis.cpp
index 77b09fb15316e..bb54c0986c20f 100644
--- a/llvm/lib/Analysis/DependenceAnalysis.cpp
+++ b/llvm/lib/Analysis/DependenceAnalysis.cpp
@@ -2590,23 +2590,6 @@ bool DependenceInfo::gcdMIVtest(const SCEV *Src, const SCEV *Dst,
   const SCEV *Delta = SE->getMinusSCEV(DstConst, SrcConst);
   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();
diff --git a/llvm/test/Analysis/DependenceAnalysis/gcd-miv-overflow.ll b/llvm/test/Analysis/DependenceAnalysis/gcd-miv-overflow.ll
index 618d14c75faad..f6b23f18df738 100644
--- a/llvm/test/Analysis/DependenceAnalysis/gcd-miv-overflow.ll
+++ b/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
@@ -143,7 +142,7 @@ 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!
 ;
@@ -151,7 +150,7 @@ define void @gcdmiv_const_ovfl(ptr %A, i64 %m) {
 ; 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 [*]!
 ;