[llvm] [IRCE] Fix '"Instruction does not dominate all uses!" after IRCE pass #63984' (PR #136505)

[via llvm-commits]

https://github.com/Zentrik updated https://github.com/llvm/llvm-project/pull/136505

>From 785d00ee5771cf842643f80f262b32f160b24aed Mon Sep 17 00:00:00 2001
From: Zentrik <llvm.zentrik at gmail.com>
Date: Sun, 20 Apr 2025 20:50:02 +0100
Subject: [PATCH 1/3] IRCE: Fix '"Instruction does not dominate all uses!"
 after IRCE pass #63984'

---
 .../Scalar/InductiveRangeCheckElimination.cpp       | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/llvm/lib/Transforms/Scalar/InductiveRangeCheckElimination.cpp b/llvm/lib/Transforms/Scalar/InductiveRangeCheckElimination.cpp
index e706a6f83b1e7..4da816bea5870 100644
--- a/llvm/lib/Transforms/Scalar/InductiveRangeCheckElimination.cpp
+++ b/llvm/lib/Transforms/Scalar/InductiveRangeCheckElimination.cpp
@@ -265,8 +265,13 @@ bool InductiveRangeCheck::parseRangeCheckICmp(Loop *L, ICmpInst *ICI,
                                               ScalarEvolution &SE,
                                               const SCEVAddRecExpr *&Index,
                                               const SCEV *&End) {
-  auto IsLoopInvariant = [&SE, L](Value *V) {
-    return SE.isLoopInvariant(SE.getSCEV(V), L);
+  auto IsLoopInvariantAndNotUndef = [&SE, L](Value *V) {
+    const SCEV *S = SE.getSCEV(V);
+
+    if (isa<SCEVCouldNotCompute>(S))
+      return false;
+
+    return SE.isLoopInvariant(SE.getSCEV(V), L) && !SE.containsUndefs(S);
   };
 
   ICmpInst::Predicate Pred = ICI->getPredicate();
@@ -277,10 +282,10 @@ bool InductiveRangeCheck::parseRangeCheckICmp(Loop *L, ICmpInst *ICI,
     return false;
 
   // Canonicalize to the `Index Pred Invariant` comparison
-  if (IsLoopInvariant(LHS)) {
+  if (IsLoopInvariantAndNotUndef(LHS)) {
     std::swap(LHS, RHS);
     Pred = CmpInst::getSwappedPredicate(Pred);
-  } else if (!IsLoopInvariant(RHS))
+  } else if (!IsLoopInvariantAndNotUndef(RHS))
     // Both LHS and RHS are loop variant
     return false;
 

>From b167a5ac25373b9232c0544df3247d23b34b2384 Mon Sep 17 00:00:00 2001
From: Zentrik <llvm.zentrik at gmail.com>
Date: Mon, 21 Apr 2025 09:47:03 +0100
Subject: [PATCH 2/3] Add test following
 `llvm-project/llvm/test/Transforms/IRCE/pr89959.ll`

---
 llvm/test/Transforms/IRCE/undef.ll | 58 ++++++++++++++++++++++++++++++
 1 file changed, 58 insertions(+)
 create mode 100644 llvm/test/Transforms/IRCE/undef.ll

diff --git a/llvm/test/Transforms/IRCE/undef.ll b/llvm/test/Transforms/IRCE/undef.ll
new file mode 100644
index 0000000000000..22d6c32a02347
--- /dev/null
+++ b/llvm/test/Transforms/IRCE/undef.ll
@@ -0,0 +1,58 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; RUN: opt -passes=irce -S < %s 2>&1 | FileCheck %s
+
+; Make sure we don't crash.
+define swiftcc void @wombat() {
+; CHECK-LABEL: define swiftcc void @wombat() {
+; CHECK-NEXT:  [[BB:.*]]:
+; CHECK-NEXT:    br label %[[BB1:.*]]
+; CHECK:       [[BB1]]:
+; CHECK-NEXT:    [[PHI:%.*]] = phi i64 [ [[ADD:%.*]], %[[BB7:.*]] ], [ 1, %[[BB]] ]
+; CHECK-NEXT:    [[ICMP:%.*]] = icmp ult i64 [[PHI]], undef
+; CHECK-NEXT:    br i1 [[ICMP]], label %[[BB3:.*]], label %[[BB2:.*]]
+; CHECK:       [[BB2]]:
+; CHECK-NEXT:    unreachable
+; CHECK:       [[BB3]]:
+; CHECK-NEXT:    [[CALL5:%.*]] = call token (...) @llvm.gc_preserve_begin(ptr null)
+; CHECK-NEXT:    br i1 true, label %[[BB7]], label %[[BB6:.*]]
+; CHECK:       [[BB6]]:
+; CHECK-NEXT:    call void @llvm.gc_preserve_end(token [[CALL5]])
+; CHECK-NEXT:    unreachable
+; CHECK:       [[BB7]]:
+; CHECK-NEXT:    [[ICMP8:%.*]] = icmp eq i64 [[PHI]], 1
+; CHECK-NEXT:    [[ADD]] = add i64 [[PHI]], 1
+; CHECK-NEXT:    br i1 [[ICMP8]], label %[[BB9:.*]], label %[[BB1]]
+; CHECK:       [[BB9]]:
+; CHECK-NEXT:    unreachable
+;
+bb:
+  br label %bb1
+
+bb1:                                              ; preds = %bb7, %bb
+  %phi = phi i64 [ %add, %bb7 ], [ 1, %bb ]
+  %icmp = icmp ult i64 %phi, undef
+  br i1 %icmp, label %bb3, label %bb2
+
+bb2:                                              ; preds = %bb1
+  unreachable
+
+bb3:                                              ; preds = %bb1
+  %call5 = call token (...) @llvm.gc_preserve_begin(ptr null)
+  br i1 false, label %bb6, label %bb7
+
+bb6:                                              ; preds = %bb3
+  call void @llvm.gc_preserve_end(token %call5)
+  unreachable
+
+bb7:                                              ; preds = %bb3
+  %icmp8 = icmp eq i64 %phi, 1
+  %add = add i64 %phi, 1
+  br i1 %icmp8, label %bb9, label %bb1
+
+bb9:                                              ; preds = %bb7
+  unreachable
+}
+
+declare token @llvm.gc_preserve_begin(...)
+
+declare void @llvm.gc_preserve_end(token)

>From 4609f3782f705ee319286fa523fe252ae310dff3 Mon Sep 17 00:00:00 2001
From: Zentrik <llvm.zentrik at gmail.com>
Date: Mon, 21 Apr 2025 10:01:30 +0100
Subject: [PATCH 3/3] Simplify code

---
 .../Transforms/Scalar/InductiveRangeCheckElimination.cpp    | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/llvm/lib/Transforms/Scalar/InductiveRangeCheckElimination.cpp b/llvm/lib/Transforms/Scalar/InductiveRangeCheckElimination.cpp
index 4da816bea5870..4d0e5a61db9a4 100644
--- a/llvm/lib/Transforms/Scalar/InductiveRangeCheckElimination.cpp
+++ b/llvm/lib/Transforms/Scalar/InductiveRangeCheckElimination.cpp
@@ -267,11 +267,7 @@ bool InductiveRangeCheck::parseRangeCheckICmp(Loop *L, ICmpInst *ICI,
                                               const SCEV *&End) {
   auto IsLoopInvariantAndNotUndef = [&SE, L](Value *V) {
     const SCEV *S = SE.getSCEV(V);
-
-    if (isa<SCEVCouldNotCompute>(S))
-      return false;
-
-    return SE.isLoopInvariant(SE.getSCEV(V), L) && !SE.containsUndefs(S);
+    return SE.isLoopInvariant(S, L) && !SE.containsUndefs(S);
   };
 
   ICmpInst::Predicate Pred = ICI->getPredicate();