[PATCH] D87854: [SCEV] Use information from assume for BE taken count.

[Florian Hahn via Phabricator via llvm-commits]

fhahn updated this revision to Diff 294372.
fhahn added a comment.

In D87854#2280261 <https://reviews.llvm.org/D87854#2280261>, @jdoerfert wrote:

> commit message?

It was not quite ready yet, but now everything should be in place and this patch only contains the important change. I'll update the title/description shortly after updating the diff.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D87854/new/

https://reviews.llvm.org/D87854

Files:
  llvm/lib/Analysis/ScalarEvolution.cpp
  llvm/test/Analysis/ScalarEvolution/max-backedge-taken-count-guard-info.ll


Index: llvm/test/Analysis/ScalarEvolution/max-backedge-taken-count-guard-info.ll
===================================================================
--- llvm/test/Analysis/ScalarEvolution/max-backedge-taken-count-guard-info.ll
+++ llvm/test/Analysis/ScalarEvolution/max-backedge-taken-count-guard-info.ll
@@ -278,7 +278,7 @@
 define void @test_guard_and_assume(i32* nocapture readonly %data, i64 %count) {
 ; CHECK-LABEL: @test_guard_and_assume
 ; CHECK:       Loop %loop: backedge-taken count is (-1 + %count)
-; CHECK-NEXT:  Loop %loop: max backedge-taken count is -2
+; CHECK-NEXT:  Loop %loop: max backedge-taken count is 3
 ; CHECK-NEXT:  Loop %loop: Predicated backedge-taken count is (-1 + %count)
 ;
 entry:
Index: llvm/lib/Analysis/ScalarEvolution.cpp
===================================================================
--- llvm/lib/Analysis/ScalarEvolution.cpp
+++ llvm/lib/Analysis/ScalarEvolution.cpp
@@ -12658,6 +12658,18 @@
                      getSCEV(Cmp->getOperand(1)), RewriteMap);
   }
 
+  // Also collect information from assumptions dominating the loop.
+  for (auto &AssumeVH : AC.assumptions()) {
+    if (!AssumeVH)
+      continue;
+    auto *AssumeI = cast<CallInst>(AssumeVH);
+    auto *Cmp = dyn_cast<ICmpInst>(AssumeI->getOperand(0));
+    if (!Cmp || !DT.dominates(AssumeI, L->getHeader()))
+      continue;
+    CollectCondition(Cmp->getPredicate(), getSCEV(Cmp->getOperand(0)),
+                     getSCEV(Cmp->getOperand(1)), RewriteMap);
+  }
+
   if (RewriteMap.empty())
     return Expr;
   return SCEVParameterRewriter::rewrite(Expr, *this, RewriteMap);


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