[PATCH] D79893: [SCEV] Constant fold MultExpr before applying depth limit.

[Denis Antrushin via Phabricator via llvm-commits]

dantrushin updated this revision to Diff 265145.
dantrushin added a comment.

Only ignore depth limit for all-constant expressions


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D79893/new/

https://reviews.llvm.org/D79893

Files:
  llvm/lib/Analysis/ScalarEvolution.cpp
  llvm/test/Analysis/ScalarEvolution/depth-limit-overrun.ll


Index: llvm/test/Analysis/ScalarEvolution/depth-limit-overrun.ll
===================================================================
--- /dev/null
+++ llvm/test/Analysis/ScalarEvolution/depth-limit-overrun.ll
@@ -0,0 +1,68 @@
+; RUN: opt -passes 'strength-reduce' -scalar-evolution-max-arith-depth=2 -S < %s | FileCheck %s
+; RUN: opt -loop-reduce -scalar-evolution-max-arith-depth=2 -S < %s | FileCheck %s
+
+; This test should just compile cleanly without assertions.
+
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128-ni:1-p2:32:8:8:32-ni:2"
+
+define void @test(i32 %A, i32 %B, i32 %C) {
+; CHECK-LABEL: @test(
+; CHECK:       inner_loop:
+; CHECK-NEXT:    [[LSR_IV3:%.*]] = phi i32
+; CHECK-NEXT:    [[LSR_IV1:%.*]] = phi i32
+; CHECK-NEXT:    [[LSR_IV:%.*]] = phi i32
+; CHECK:         [[LSR_IV_NEXT:%.*]] = add i32 [[LSR_IV]], 3
+; CHECK-NEXT:    [[LSR_IV_NEXT2:%.*]] = add i32 [[LSR_IV1]], 3
+; CHECK-NEXT:    [[LSR_IV_NEXT4:%.*]] = add i32 [[LSR_IV3]], -3
+;
+entry:
+  br label %outer_loop
+
+outer_loop:
+  %phi2 = phi i32 [ %A, %entry ], [ 204, %outer_tail ]
+  %phi3 = phi i32 [ %A, %entry ], [ 243, %outer_tail ]
+  %phi4 = phi i32 [ %B, %entry ], [ %i35, %outer_tail ]
+  br label %guard
+
+guard:
+  %lcmp.mod = icmp eq i32 %C, 0
+  br i1 %lcmp.mod, label %outer_tail, label %preheader
+
+preheader:
+  %i15 = shl i32 %B, 1
+  br label %inner_loop
+
+inner_loop:
+  %phi5 = phi i32 [ %phi3, %preheader ], [ %i30, %inner_loop ]
+  %phi6 = phi i32 [ %phi2, %preheader ], [ %i33, %inner_loop ]
+  %iter = phi i32 [ %C, %preheader ], [ %iter.sub, %inner_loop ]
+  %i17 = sub i32 %phi4, %phi6
+  %i18 = sub i32 14, %phi5
+  %i19 = mul i32 %i18, %C
+  %factor.prol = shl i32 %phi5, 1
+  %i20 = add i32 %i17, %factor.prol
+  %i21 = add i32 %i20, %B
+  %i22 = add i32 %i21, %i19
+  %i23 = sub i32 14, %i22
+  %i24 = mul i32 %i23, %C
+  %factor.1.prol = shl i32 %i22, 1
+  %i25 = add i32 %i17, %factor.1.prol
+  %i27 = add i32 %i25, %i24
+  %i29 = mul i32 %i25, %C
+  %factor.2.prol = shl i32 %i27, 1
+  %i30 = add i32 %i17, %factor.2.prol
+  %i33 = add nsw i32 %phi6, -3
+  %iter.sub = add i32 %iter, -1
+  %iter.cmp = icmp eq i32 %iter.sub, 0
+  br i1 %iter.cmp, label %outer_tail, label %inner_loop
+
+outer_tail:
+  %phi7 = phi i32 [ %phi2, %guard ], [ %i33, %inner_loop ]
+  %i35 = sub i32 %A, %phi7
+  %cmp = icmp sgt i32 %i35, 9876
+  br i1 %cmp, label %exit, label %outer_loop
+
+exit:
+  ret void
+
+}
Index: llvm/lib/Analysis/ScalarEvolution.cpp
===================================================================
--- llvm/lib/Analysis/ScalarEvolution.cpp
+++ llvm/lib/Analysis/ScalarEvolution.cpp
@@ -2932,8 +2932,12 @@
   Flags = StrengthenNoWrapFlags(this, scMulExpr, Ops, Flags);
 
   // Limit recursion calls depth.
-  if (Depth > MaxArithDepth || hasHugeExpression(Ops))
-    return getOrCreateMulExpr(Ops, Flags);
+  if (Depth > MaxArithDepth || hasHugeExpression(Ops)) {
+    bool AllConst =
+        llvm::all_of(Ops, [](const SCEV *S) { return isa<SCEVConstant>(S); });
+    if (!AllConst)
+      return getOrCreateMulExpr(Ops, Flags);
+  }
 
   if (SCEV *S = std::get<0>(findExistingSCEVInCache(scMulExpr, Ops))) {
     static_cast<SCEVMulExpr *>(S)->setNoWrapFlags(Flags);


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