[PATCH] D129297: [LSR] Fix bug - check if loop has preheader before calling isInductionPHI

[Zaara Syeda via Phabricator via llvm-commits]

This revision was landed with ongoing or failed builds.
This revision was automatically updated to reflect the committed changes.
Closed by commit rG58b9666dc1a0: [LSR] Fix bug - check if loop has preheader before calling isInductionPHI (authored by syzaara).

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D129297/new/

https://reviews.llvm.org/D129297

Files:
  llvm/lib/Transforms/Utils/LoopUtils.cpp
  llvm/test/Transforms/LoopStrengthReduce/remove_scev_indvars.ll


Index: llvm/test/Transforms/LoopStrengthReduce/remove_scev_indvars.ll
===================================================================
--- llvm/test/Transforms/LoopStrengthReduce/remove_scev_indvars.ll
+++ llvm/test/Transforms/LoopStrengthReduce/remove_scev_indvars.ll
@@ -91,3 +91,24 @@
 dead:                                             ; No predecessors!
   br label %for.cond6403
 }
+
+
+; Check that this doesn't crash
+define void @kernfs_path_from_node() {
+entry:
+  callbr void asm sideeffect "", "i"(i8* blockaddress(@kernfs_path_from_node, %while.body))
+          to label %asm.fallthrough [label %while.body]
+
+asm.fallthrough:                                  ; preds = %entry
+  br label %while.body
+
+while.body:                                       ; preds = %while.body, %asm.fallthrough, %entry
+  %depth.04 = phi i32 [ %inc, %while.body ], [ 0, %asm.fallthrough ], [ 0, %entry ]
+  %inc = add i32 %depth.04, 1
+  br i1 false, label %while.end, label %while.body
+
+while.end:                                        ; preds = %while.body
+  %inc.lcssa = phi i32 [ %depth.04, %while.body ]
+  store i32 %inc.lcssa, i32* null, align 4
+  ret void
+}
Index: llvm/lib/Transforms/Utils/LoopUtils.cpp
===================================================================
--- llvm/lib/Transforms/Utils/LoopUtils.cpp
+++ llvm/lib/Transforms/Utils/LoopUtils.cpp
@@ -1243,6 +1243,20 @@
   return true;
 }
 
+/// Checks if it is safe to call InductionDescriptor::isInductionPHI for \p Phi,
+/// and returns true if this Phi is an induction phi in the loop. When
+/// isInductionPHI returns true, \p ID will be also be set by isInductionPHI.
+static bool checkIsIndPhi(PHINode *Phi, Loop *L, ScalarEvolution *SE,
+                          InductionDescriptor &ID) {
+  if (!Phi)
+    return false;
+  if (!L->getLoopPreheader())
+    return false;
+  if (Phi->getParent() != L->getHeader())
+    return false;
+  return InductionDescriptor::isInductionPHI(Phi, L, SE, ID);
+}
+
 int llvm::rewriteLoopExitValues(Loop *L, LoopInfo *LI, TargetLibraryInfo *TLI,
                                 ScalarEvolution *SE,
                                 const TargetTransformInfo *TTI,
@@ -1303,10 +1317,7 @@
           InductionDescriptor ID;
           PHINode *IndPhi = dyn_cast<PHINode>(Inst);
           if (IndPhi) {
-            if (IndPhi->getParent() != L->getHeader())
-              continue;
-            // Do not consider non induction phis.
-            if (!InductionDescriptor::isInductionPHI(IndPhi, L, SE, ID))
+            if (!checkIsIndPhi(IndPhi, L, SE, ID))
               continue;
             // This is an induction PHI. Check that the only users are PHI
             // nodes, and induction variable update binary operators.
@@ -1327,12 +1338,8 @@
               continue;
             if (llvm::any_of(Inst->users(), [&](User *U) {
                   PHINode *Phi = dyn_cast<PHINode>(U);
-                  if (!Phi)
+                  if (Phi != PN && !checkIsIndPhi(Phi, L, SE, ID))
                     return true;
-                  if (Phi->getParent() == L->getHeader()) {
-                    if (!InductionDescriptor::isInductionPHI(Phi, L, SE, ID))
-                      return true;
-                  }
                   return false;
                 }))
               continue;


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