[llvm] [LoopPeel] Handle non-local instructions/arguments when updating exiting values (PR #142993)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-transforms

Author: Yingwei Zheng (dtcxzyw)

<details>
<summary>Changes</summary>

Similar to https://github.com/llvm/llvm-project/commit/7e14161f49b32387988cf9d937bbfaa27d0fbdd5, the exiting value may be a non-local instruction or an argument.

Closes https://github.com/llvm/llvm-project/issues/142895.

---
Full diff: https://github.com/llvm/llvm-project/pull/142993.diff


2 Files Affected:

- (modified) llvm/lib/Transforms/Utils/LoopPeel.cpp (+5-1) 
- (modified) llvm/test/Transforms/LoopUnroll/unroll-and-peel-last-iteration.ll (+41) 


``````````diff
diff --git a/llvm/lib/Transforms/Utils/LoopPeel.cpp b/llvm/lib/Transforms/Utils/LoopPeel.cpp
index bd025fddd0cf7..9149f71941db4 100644
--- a/llvm/lib/Transforms/Utils/LoopPeel.cpp
+++ b/llvm/lib/Transforms/Utils/LoopPeel.cpp
@@ -1257,7 +1257,11 @@ bool llvm::peelLoop(Loop *L, unsigned PeelCount, bool PeelLast, LoopInfo *LI,
     // Now adjust users of the original exit values by replacing them with the
     // exit value from the peeled iteration and remove them.
     for (const auto &[P, E] : ExitValues) {
-      P->replaceAllUsesWith(isa<Constant>(E) ? E : &*VMap.lookup(E));
+      Instruction *ExitInst = dyn_cast<Instruction>(E);
+      if (ExitInst && L->contains(ExitInst))
+        P->replaceAllUsesWith(&*VMap[ExitInst]);
+      else
+        P->replaceAllUsesWith(E);
       P->eraseFromParent();
     }
     formLCSSA(*L, DT, LI, SE);
diff --git a/llvm/test/Transforms/LoopUnroll/unroll-and-peel-last-iteration.ll b/llvm/test/Transforms/LoopUnroll/unroll-and-peel-last-iteration.ll
index 7d38c18d10667..f07afaf1b207f 100644
--- a/llvm/test/Transforms/LoopUnroll/unroll-and-peel-last-iteration.ll
+++ b/llvm/test/Transforms/LoopUnroll/unroll-and-peel-last-iteration.ll
@@ -71,6 +71,47 @@ exit:
   ret i32 %1
 }
 
+; Test case for https://github.com/llvm/llvm-project/issues/142895.
+
+define i32 @pr142895_exit_value_is_arg(i32 %arg) {
+entry:
+  br label %for.cond.preheader
+
+for.cond.preheader:
+  %indvar = phi i32 [ 0, %entry ], [ %inc, %for.cond.preheader ]
+  %cmp1 = icmp eq i32 %indvar, 32
+  %sel = select i1 %cmp1, i32 0, i32 0
+  %sub = sub i32 0, 0
+  %xor = xor i32 0, 0
+  %inc = add i32 %indvar, 1
+  %exitcond = icmp ne i32 %inc, 33
+  br i1 %exitcond, label %for.cond.preheader, label %for.cond.cleanup
+
+for.cond.cleanup:
+  %exit.lcssa = phi i32 [ %arg, %for.cond.preheader ]
+  ret i32 %exit.lcssa
+}
+
+define i32 @pr142895_exit_value_is_inst(i32 %arg) {
+entry:
+  %mul = mul i32 %arg, 7
+  br label %for.cond.preheader
+
+for.cond.preheader:
+  %indvar = phi i32 [ 0, %entry ], [ %inc, %for.cond.preheader ]
+  %cmp1 = icmp eq i32 %indvar, 32
+  %sel = select i1 %cmp1, i32 0, i32 0
+  %sub = sub i32 0, 0
+  %xor = xor i32 0, 0
+  %inc = add i32 %indvar, 1
+  %exitcond = icmp ne i32 %inc, 33
+  br i1 %exitcond, label %for.cond.preheader, label %for.cond.cleanup
+
+for.cond.cleanup:
+  %exit.lcssa = phi i32 [ %mul, %for.cond.preheader ]
+  ret i32 %exit.lcssa
+}
+
 declare void @foo(i32)
 ;.
 ; CHECK: [[LOOP0]] = distinct !{[[LOOP0]], [[META1:![0-9]+]]}

``````````

</details>


https://github.com/llvm/llvm-project/pull/142993