[PATCH] D137822: [IRCE] Bail out if Start AddRec is for another loop

[Dmitry Makogon via Phabricator via llvm-commits]

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Imagine we have an outer loop and an inner loop, which is in the outer one, and a range check in outer loop of such addrec:

  {{0,+,1}<%outer_header>,+,1}<%inner_header>

When IRCE runs on the outer loop it sees the range check and tries to check whether it is possible to safely calculate the loop bound.
However, this addrec is for the inner loop, so we shouldn't do anything at all.

Fixes https://github.com/llvm/llvm-project/issues/58912


https://reviews.llvm.org/D137822

Files:
  llvm/lib/Transforms/Scalar/InductiveRangeCheckElimination.cpp
  llvm/test/Transforms/IRCE/iv-for-another-loop.ll


Index: llvm/test/Transforms/IRCE/iv-for-another-loop.ll
===================================================================
--- llvm/test/Transforms/IRCE/iv-for-another-loop.ll
+++ llvm/test/Transforms/IRCE/iv-for-another-loop.ll
@@ -4,7 +4,7 @@
 target triple = "x86_64-unknown-linux-gnu"
 
 ; REQUIRES: asserts
-; XFAIL: *
+; CHECK-NOT: irce
 
 define void @test() {
 bb:
Index: llvm/lib/Transforms/Scalar/InductiveRangeCheckElimination.cpp
===================================================================
--- llvm/lib/Transforms/Scalar/InductiveRangeCheckElimination.cpp
+++ llvm/lib/Transforms/Scalar/InductiveRangeCheckElimination.cpp
@@ -845,6 +845,10 @@
   // induction variable satisfies some constraint.
 
   const SCEVAddRecExpr *IndVarBase = cast<SCEVAddRecExpr>(LeftSCEV);
+  if (IndVarBase->getLoop() != &L) {
+    FailureReason = "LHS in icmp not induction variable for this loop";
+    return None;
+  }
   if (!IndVarBase->isAffine()) {
     FailureReason = "LHS in icmp not induction variable";
     return None;


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