[llvm] Reapply "StructurizeCFG: Optimize phi insertion during ssa reconstruction (#101301)" (PR #114347)

via llvm-commits llvm-commits at lists.llvm.org
Wed Oct 30 20:41:25 PDT 2024


llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-transforms

Author: Ruiling, Song (ruiling)

<details>
<summary>Changes</summary>

This reverts commit be40c723ce2b7bf2690d22039d74d21b2bd5b7cf.

---

Patch is 26.95 KiB, truncated to 20.00 KiB below, full version: https://github.com/llvm/llvm-project/pull/114347.diff


6 Files Affected:

- (modified) llvm/lib/Transforms/Scalar/StructurizeCFG.cpp (+115-18) 
- (modified) llvm/test/CodeGen/AMDGPU/GlobalISel/divergence-divergent-i1-used-outside-loop.ll (+2-4) 
- (modified) llvm/test/CodeGen/AMDGPU/agpr-copy-no-free-registers.ll (+9-17) 
- (modified) llvm/test/CodeGen/AMDGPU/while-break.ll (+5-8) 
- (modified) llvm/test/Transforms/StructurizeCFG/AMDGPU/loop-subregion-misordered.ll (+11-12) 
- (modified) llvm/test/Transforms/StructurizeCFG/loop-break-phi.ll (+26-37) 


``````````diff
diff --git a/llvm/lib/Transforms/Scalar/StructurizeCFG.cpp b/llvm/lib/Transforms/Scalar/StructurizeCFG.cpp
index 92e47cbc7ae8bf..90c18c0b9c01ce 100644
--- a/llvm/lib/Transforms/Scalar/StructurizeCFG.cpp
+++ b/llvm/lib/Transforms/Scalar/StructurizeCFG.cpp
@@ -8,6 +8,7 @@
 
 #include "llvm/Transforms/Scalar/StructurizeCFG.h"
 #include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/EquivalenceClasses.h"
 #include "llvm/ADT/MapVector.h"
 #include "llvm/ADT/SCCIterator.h"
 #include "llvm/ADT/STLExtras.h"
@@ -325,6 +326,10 @@ class StructurizeCFG {
   void findUndefBlocks(BasicBlock *PHIBlock,
                        const SmallSet<BasicBlock *, 8> &Incomings,
                        SmallVector<BasicBlock *> &UndefBlks) const;
+
+  void mergeIfCompatible(EquivalenceClasses<PHINode *> &PhiClasses, PHINode *A,
+                         PHINode *B);
+
   void setPhiValues();
 
   void simplifyAffectedPhis();
@@ -755,10 +760,102 @@ void StructurizeCFG::findUndefBlocks(
   }
 }
 
+// If two phi nodes have compatible incoming values (for each
+// incoming block, either they have the same incoming value or only one phi
+// node has an incoming value), let them share the merged incoming values. The
+// merge process is guided by the equivalence information from \p PhiClasses.
+// The function will possibly update the incoming values of leader phi in
+// DeletedPhis.
+void StructurizeCFG::mergeIfCompatible(
+    EquivalenceClasses<PHINode *> &PhiClasses, PHINode *A, PHINode *B) {
+  auto ItA = PhiClasses.findLeader(PhiClasses.insert(A));
+  auto ItB = PhiClasses.findLeader(PhiClasses.insert(B));
+  // They are already in the same class, no work needed.
+  if (ItA == ItB)
+    return;
+
+  PHINode *LeaderA = *ItA;
+  PHINode *LeaderB = *ItB;
+  BBValueVector &IncomingA = DeletedPhis[LeaderA->getParent()][LeaderA];
+  BBValueVector &IncomingB = DeletedPhis[LeaderB->getParent()][LeaderB];
+
+  DenseMap<BasicBlock *, Value *> Mergeable(IncomingA.begin(), IncomingA.end());
+  for (auto [BB, V] : IncomingB) {
+    auto BBIt = Mergeable.find(BB);
+    if (BBIt != Mergeable.end() && BBIt->second != V)
+      return;
+    // Either IncomingA does not have this value or IncomingA has the same
+    // value.
+    Mergeable.insert({BB, V});
+  }
+
+  // Update the incoming value of leaderA.
+  IncomingA.assign(Mergeable.begin(), Mergeable.end());
+  PhiClasses.unionSets(ItA, ItB);
+}
+
 /// Add the real PHI value as soon as everything is set up
 void StructurizeCFG::setPhiValues() {
   SmallVector<PHINode *, 8> InsertedPhis;
   SSAUpdater Updater(&InsertedPhis);
+  DenseMap<BasicBlock *, SmallVector<BasicBlock *>> UndefBlksMap;
+
+  // Find phi nodes that have compatible incoming values (either they have
+  // the same value for the same block or only one phi node has an incoming
+  // value, see example below). We only search again the phi's that are
+  // referenced by another phi, which is the case we care about.
+  //
+  // For example (-- means no incoming value):
+  // phi1 : BB1:phi2   BB2:v  BB3:--
+  // phi2:  BB1:--     BB2:v  BB3:w
+  //
+  // Then we can merge these incoming values and let phi1, phi2 use the
+  // same set of incoming values:
+  //
+  // phi1&phi2: BB1:phi2  BB2:v  BB3:w
+  //
+  // By doing this, phi1 and phi2 would share more intermediate phi nodes.
+  // This would help reduce the number of phi nodes during SSA reconstruction
+  // and ultimately result in fewer COPY instructions.
+  //
+  // This should be correct, because if a phi node does not have incoming
+  // value from certain block, this means the block is not the predecessor
+  // of the parent block, so we actually don't care about its incoming value.
+  EquivalenceClasses<PHINode *> PhiClasses;
+  for (const auto &[To, From] : AddedPhis) {
+    auto OldPhiIt = DeletedPhis.find(To);
+    if (OldPhiIt == DeletedPhis.end())
+      continue;
+
+    PhiMap &BlkPhis = OldPhiIt->second;
+    SmallVector<BasicBlock *> &UndefBlks = UndefBlksMap[To];
+    SmallSet<BasicBlock *, 8> Incomings;
+
+    // Get the undefined blocks shared by all the phi nodes.
+    if (!BlkPhis.empty()) {
+      for (const auto &VI : BlkPhis.front().second)
+        Incomings.insert(VI.first);
+      findUndefBlocks(To, Incomings, UndefBlks);
+    }
+
+    for (const auto &[Phi, Incomings] : OldPhiIt->second) {
+      SmallVector<PHINode *> IncomingPHIs;
+      for (const auto &[BB, V] : Incomings) {
+        // First, for each phi, check whether it has incoming value which is
+        // another phi.
+        if (PHINode *P = dyn_cast<PHINode>(V))
+          IncomingPHIs.push_back(P);
+      }
+
+      for (auto *OtherPhi : IncomingPHIs) {
+        // Skip phis that are unrelated to the phi reconstruction for now.
+        if (!DeletedPhis.contains(OtherPhi->getParent()))
+          continue;
+        mergeIfCompatible(PhiClasses, Phi, OtherPhi);
+      }
+    }
+  }
+
   for (const auto &AddedPhi : AddedPhis) {
     BasicBlock *To = AddedPhi.first;
     const BBVector &From = AddedPhi.second;
@@ -766,28 +863,27 @@ void StructurizeCFG::setPhiValues() {
     if (!DeletedPhis.count(To))
       continue;
 
-    SmallVector<BasicBlock *> UndefBlks;
-    bool CachedUndefs = false;
     PhiMap &Map = DeletedPhis[To];
-    for (const auto &PI : Map) {
-      PHINode *Phi = PI.first;
+    SmallVector<BasicBlock *> &UndefBlks = UndefBlksMap[To];
+    for (const auto &[Phi, Incoming] : Map) {
       Value *Undef = UndefValue::get(Phi->getType());
       Updater.Initialize(Phi->getType(), "");
       Updater.AddAvailableValue(&Func->getEntryBlock(), Undef);
       Updater.AddAvailableValue(To, Undef);
 
-      SmallSet<BasicBlock *, 8> Incomings;
-      SmallVector<BasicBlock *> ConstantPreds;
-      for (const auto &VI : PI.second) {
-        Incomings.insert(VI.first);
-        Updater.AddAvailableValue(VI.first, VI.second);
-        if (isa<Constant>(VI.second))
-          ConstantPreds.push_back(VI.first);
-      }
+      // Use leader phi's incoming if there is.
+      auto LeaderIt = PhiClasses.findLeader(Phi);
+      bool UseIncomingOfLeader =
+          LeaderIt != PhiClasses.member_end() && *LeaderIt != Phi;
+      const auto &IncomingMap =
+          UseIncomingOfLeader ? DeletedPhis[(*LeaderIt)->getParent()][*LeaderIt]
+                              : Incoming;
 
-      if (!CachedUndefs) {
-        findUndefBlocks(To, Incomings, UndefBlks);
-        CachedUndefs = true;
+      SmallVector<BasicBlock *> ConstantPreds;
+      for (const auto &[BB, V] : IncomingMap) {
+        Updater.AddAvailableValue(BB, V);
+        if (isa<Constant>(V))
+          ConstantPreds.push_back(BB);
       }
 
       for (auto UB : UndefBlks) {
@@ -798,6 +894,10 @@ void StructurizeCFG::setPhiValues() {
         if (any_of(ConstantPreds,
                    [&](BasicBlock *CP) { return DT->dominates(CP, UB); }))
           continue;
+        // Maybe already get a value through sharing with other phi nodes.
+        if (Updater.HasValueForBlock(UB))
+          continue;
+
         Updater.AddAvailableValue(UB, Undef);
       }
 
@@ -805,10 +905,7 @@ void StructurizeCFG::setPhiValues() {
         Phi->setIncomingValueForBlock(FI, Updater.GetValueAtEndOfBlock(FI));
       AffectedPhis.push_back(Phi);
     }
-
-    DeletedPhis.erase(To);
   }
-  assert(DeletedPhis.empty());
 
   AffectedPhis.append(InsertedPhis.begin(), InsertedPhis.end());
 }
diff --git a/llvm/test/CodeGen/AMDGPU/GlobalISel/divergence-divergent-i1-used-outside-loop.ll b/llvm/test/CodeGen/AMDGPU/GlobalISel/divergence-divergent-i1-used-outside-loop.ll
index b27d8fdc24ff73..935200d5953072 100644
--- a/llvm/test/CodeGen/AMDGPU/GlobalISel/divergence-divergent-i1-used-outside-loop.ll
+++ b/llvm/test/CodeGen/AMDGPU/GlobalISel/divergence-divergent-i1-used-outside-loop.ll
@@ -298,7 +298,7 @@ define void @divergent_i1_icmp_used_outside_loop(i32 %v0, i32 %v1, ptr addrspace
 ; GFX10-NEXT:    s_waitcnt vmcnt(0) expcnt(0) lgkmcnt(0)
 ; GFX10-NEXT:    s_mov_b32 s5, 0
 ; GFX10-NEXT:    ; implicit-def: $sgpr6
-; GFX10-NEXT:    v_mov_b32_e32 v5, s5
+; GFX10-NEXT:    v_mov_b32_e32 v4, s5
 ; GFX10-NEXT:    s_branch .LBB4_2
 ; GFX10-NEXT:  .LBB4_1: ; %Flow
 ; GFX10-NEXT:    ; in Loop: Header=BB4_2 Depth=1
@@ -312,7 +312,6 @@ define void @divergent_i1_icmp_used_outside_loop(i32 %v0, i32 %v1, ptr addrspace
 ; GFX10-NEXT:    s_cbranch_execz .LBB4_6
 ; GFX10-NEXT:  .LBB4_2: ; %cond.block.0
 ; GFX10-NEXT:    ; =>This Inner Loop Header: Depth=1
-; GFX10-NEXT:    v_mov_b32_e32 v4, v5
 ; GFX10-NEXT:    v_cmp_eq_u32_e32 vcc_lo, v0, v4
 ; GFX10-NEXT:    s_and_saveexec_b32 s7, vcc_lo
 ; GFX10-NEXT:    s_cbranch_execz .LBB4_4
@@ -329,12 +328,11 @@ define void @divergent_i1_icmp_used_outside_loop(i32 %v0, i32 %v1, ptr addrspace
 ; GFX10-NEXT:    s_or_b32 exec_lo, exec_lo, s7
 ; GFX10-NEXT:    v_cmp_ne_u32_e64 s4, v1, v4
 ; GFX10-NEXT:    s_mov_b32 s7, -1
-; GFX10-NEXT:    ; implicit-def: $vgpr5
 ; GFX10-NEXT:    s_and_saveexec_b32 s8, s4
 ; GFX10-NEXT:    s_cbranch_execz .LBB4_1
 ; GFX10-NEXT:  ; %bb.5: ; %loop.cond
 ; GFX10-NEXT:    ; in Loop: Header=BB4_2 Depth=1
-; GFX10-NEXT:    v_add_nc_u32_e32 v5, 1, v4
+; GFX10-NEXT:    v_add_nc_u32_e32 v4, 1, v4
 ; GFX10-NEXT:    s_andn2_b32 s4, -1, exec_lo
 ; GFX10-NEXT:    s_and_b32 s7, exec_lo, 0
 ; GFX10-NEXT:    s_or_b32 s7, s4, s7
diff --git a/llvm/test/CodeGen/AMDGPU/agpr-copy-no-free-registers.ll b/llvm/test/CodeGen/AMDGPU/agpr-copy-no-free-registers.ll
index 49b450a9af0bc9..4d26453e1a0d6d 100644
--- a/llvm/test/CodeGen/AMDGPU/agpr-copy-no-free-registers.ll
+++ b/llvm/test/CodeGen/AMDGPU/agpr-copy-no-free-registers.ll
@@ -576,11 +576,11 @@ define amdgpu_kernel void @introduced_copy_to_sgpr(i64 %arg, i32 %arg1, i32 %arg
 ; GFX908-NEXT:    v_cndmask_b32_e64 v6, 0, 1, s[0:1]
 ; GFX908-NEXT:    v_mov_b32_e32 v4, s8
 ; GFX908-NEXT:    v_cmp_ne_u32_e64 s[0:1], 1, v6
-; GFX908-NEXT:    v_mov_b32_e32 v8, s8
 ; GFX908-NEXT:    v_mov_b32_e32 v6, s8
+; GFX908-NEXT:    v_mov_b32_e32 v8, s8
 ; GFX908-NEXT:    v_mov_b32_e32 v5, s9
-; GFX908-NEXT:    v_mov_b32_e32 v9, s9
 ; GFX908-NEXT:    v_mov_b32_e32 v7, s9
+; GFX908-NEXT:    v_mov_b32_e32 v9, s9
 ; GFX908-NEXT:    v_cmp_lt_i64_e64 s[16:17], s[4:5], 0
 ; GFX908-NEXT:    v_mov_b32_e32 v11, v5
 ; GFX908-NEXT:    s_mov_b64 s[18:19], s[10:11]
@@ -641,10 +641,10 @@ define amdgpu_kernel void @introduced_copy_to_sgpr(i64 %arg, i32 %arg1, i32 %arg
 ; GFX908-NEXT:    v_add_f32_e32 v12, v20, v12
 ; GFX908-NEXT:    v_add_f32_e32 v5, v5, v25
 ; GFX908-NEXT:    v_add_f32_e32 v4, v4, v24
-; GFX908-NEXT:    v_add_f32_e32 v9, v9, v27
-; GFX908-NEXT:    v_add_f32_e32 v8, v8, v26
-; GFX908-NEXT:    v_add_f32_e32 v6, v6, v14
-; GFX908-NEXT:    v_add_f32_e32 v7, v7, v15
+; GFX908-NEXT:    v_add_f32_e32 v7, v7, v27
+; GFX908-NEXT:    v_add_f32_e32 v6, v6, v26
+; GFX908-NEXT:    v_add_f32_e32 v8, v8, v14
+; GFX908-NEXT:    v_add_f32_e32 v9, v9, v15
 ; GFX908-NEXT:    v_add_f32_e32 v10, v10, v12
 ; GFX908-NEXT:    v_add_f32_e32 v11, v11, v13
 ; GFX908-NEXT:    s_mov_b64 s[20:21], -1
@@ -654,10 +654,6 @@ define amdgpu_kernel void @introduced_copy_to_sgpr(i64 %arg, i32 %arg1, i32 %arg
 ; GFX908-NEXT:    s_andn2_b64 vcc, exec, s[20:21]
 ; GFX908-NEXT:    s_cbranch_vccz .LBB3_4
 ; GFX908-NEXT:  ; %bb.8: ; in Loop: Header=BB3_2 Depth=1
-; GFX908-NEXT:    ; implicit-def: $vgpr10_vgpr11
-; GFX908-NEXT:    ; implicit-def: $vgpr6_vgpr7
-; GFX908-NEXT:    ; implicit-def: $vgpr8_vgpr9
-; GFX908-NEXT:    ; implicit-def: $vgpr4_vgpr5
 ; GFX908-NEXT:    ; implicit-def: $vgpr2_vgpr3
 ; GFX908-NEXT:    ; implicit-def: $sgpr18_sgpr19
 ; GFX908-NEXT:  .LBB3_9: ; %loop.exit.guard
@@ -743,8 +739,8 @@ define amdgpu_kernel void @introduced_copy_to_sgpr(i64 %arg, i32 %arg1, i32 %arg
 ; GFX90A-NEXT:    v_cndmask_b32_e64 v8, 0, 1, s[0:1]
 ; GFX90A-NEXT:    v_pk_mov_b32 v[6:7], s[8:9], s[8:9] op_sel:[0,1]
 ; GFX90A-NEXT:    v_cmp_ne_u32_e64 s[0:1], 1, v8
-; GFX90A-NEXT:    v_pk_mov_b32 v[10:11], s[8:9], s[8:9] op_sel:[0,1]
 ; GFX90A-NEXT:    v_pk_mov_b32 v[8:9], s[8:9], s[8:9] op_sel:[0,1]
+; GFX90A-NEXT:    v_pk_mov_b32 v[10:11], s[8:9], s[8:9] op_sel:[0,1]
 ; GFX90A-NEXT:    v_cmp_lt_i64_e64 s[16:17], s[4:5], 0
 ; GFX90A-NEXT:    s_mov_b64 s[18:19], s[10:11]
 ; GFX90A-NEXT:    v_pk_mov_b32 v[12:13], v[6:7], v[6:7] op_sel:[0,1]
@@ -800,8 +796,8 @@ define amdgpu_kernel void @introduced_copy_to_sgpr(i64 %arg, i32 %arg1, i32 %arg
 ; GFX90A-NEXT:    v_pk_add_f32 v[16:17], v[22:23], v[16:17]
 ; GFX90A-NEXT:    v_pk_add_f32 v[14:15], v[20:21], v[14:15]
 ; GFX90A-NEXT:    v_pk_add_f32 v[6:7], v[6:7], v[24:25]
-; GFX90A-NEXT:    v_pk_add_f32 v[10:11], v[10:11], v[26:27]
-; GFX90A-NEXT:    v_pk_add_f32 v[8:9], v[8:9], v[16:17]
+; GFX90A-NEXT:    v_pk_add_f32 v[8:9], v[8:9], v[26:27]
+; GFX90A-NEXT:    v_pk_add_f32 v[10:11], v[10:11], v[16:17]
 ; GFX90A-NEXT:    v_pk_add_f32 v[12:13], v[12:13], v[14:15]
 ; GFX90A-NEXT:    s_mov_b64 s[20:21], -1
 ; GFX90A-NEXT:    s_branch .LBB3_4
@@ -810,10 +806,6 @@ define amdgpu_kernel void @introduced_copy_to_sgpr(i64 %arg, i32 %arg1, i32 %arg
 ; GFX90A-NEXT:    s_andn2_b64 vcc, exec, s[20:21]
 ; GFX90A-NEXT:    s_cbranch_vccz .LBB3_4
 ; GFX90A-NEXT:  ; %bb.8: ; in Loop: Header=BB3_2 Depth=1
-; GFX90A-NEXT:    ; implicit-def: $vgpr12_vgpr13
-; GFX90A-NEXT:    ; implicit-def: $vgpr8_vgpr9
-; GFX90A-NEXT:    ; implicit-def: $vgpr10_vgpr11
-; GFX90A-NEXT:    ; implicit-def: $vgpr6_vgpr7
 ; GFX90A-NEXT:    ; implicit-def: $vgpr4_vgpr5
 ; GFX90A-NEXT:    ; implicit-def: $sgpr18_sgpr19
 ; GFX90A-NEXT:  .LBB3_9: ; %loop.exit.guard
diff --git a/llvm/test/CodeGen/AMDGPU/while-break.ll b/llvm/test/CodeGen/AMDGPU/while-break.ll
index 46254994580d2d..9bb8a2f9f0282c 100644
--- a/llvm/test/CodeGen/AMDGPU/while-break.ll
+++ b/llvm/test/CodeGen/AMDGPU/while-break.ll
@@ -162,8 +162,8 @@ define amdgpu_ps < 2 x float> @while_break_two_chains_of_phi(float %v, i32 %x, i
 ; GCN-NEXT:    s_branch .LBB2_2
 ; GCN-NEXT:  .LBB2_1: ; %Flow1
 ; GCN-NEXT:    ; in Loop: Header=BB2_2 Depth=1
-; GCN-NEXT:    s_or_b32 exec_lo, exec_lo, s1
-; GCN-NEXT:    s_and_b32 s1, exec_lo, s4
+; GCN-NEXT:    s_or_b32 exec_lo, exec_lo, s4
+; GCN-NEXT:    s_and_b32 s1, exec_lo, s1
 ; GCN-NEXT:    s_or_b32 s2, s1, s2
 ; GCN-NEXT:    s_andn2_b32 exec_lo, exec_lo, s2
 ; GCN-NEXT:    s_cbranch_execz .LBB2_6
@@ -190,20 +190,17 @@ define amdgpu_ps < 2 x float> @while_break_two_chains_of_phi(float %v, i32 %x, i
 ; GCN-NEXT:  .LBB2_4: ; %Flow
 ; GCN-NEXT:    ; in Loop: Header=BB2_2 Depth=1
 ; GCN-NEXT:    s_or_b32 exec_lo, exec_lo, s4
-; GCN-NEXT:    v_mov_b32_e32 v7, v6
-; GCN-NEXT:    s_mov_b32 s4, -1
-; GCN-NEXT:    s_and_saveexec_b32 s1, s3
+; GCN-NEXT:    s_mov_b32 s1, -1
+; GCN-NEXT:    s_and_saveexec_b32 s4, s3
 ; GCN-NEXT:    s_cbranch_execz .LBB2_1
 ; GCN-NEXT:  ; %bb.5: ; %latch
 ; GCN-NEXT:    ; in Loop: Header=BB2_2 Depth=1
 ; GCN-NEXT:    v_cmp_lt_i32_e32 vcc_lo, s0, v3
-; GCN-NEXT:    v_mov_b32_e32 v7, v0
 ; GCN-NEXT:    s_add_i32 s0, s0, 1
-; GCN-NEXT:    s_orn2_b32 s4, vcc_lo, exec_lo
+; GCN-NEXT:    s_orn2_b32 s1, vcc_lo, exec_lo
 ; GCN-NEXT:    s_branch .LBB2_1
 ; GCN-NEXT:  .LBB2_6: ; %end
 ; GCN-NEXT:    s_or_b32 exec_lo, exec_lo, s2
-; GCN-NEXT:    v_mov_b32_e32 v0, v7
 ; GCN-NEXT:    v_mov_b32_e32 v1, v6
 ; GCN-NEXT:    ; return to shader part epilog
 entry:
diff --git a/llvm/test/Transforms/StructurizeCFG/AMDGPU/loop-subregion-misordered.ll b/llvm/test/Transforms/StructurizeCFG/AMDGPU/loop-subregion-misordered.ll
index 10a3e65e5f57d6..385e37e2750d1e 100644
--- a/llvm/test/Transforms/StructurizeCFG/AMDGPU/loop-subregion-misordered.ll
+++ b/llvm/test/Transforms/StructurizeCFG/AMDGPU/loop-subregion-misordered.ll
@@ -28,7 +28,7 @@ define amdgpu_kernel void @loop_subregion_misordered(ptr addrspace(1) %arg0) #0
 ; CHECK-NEXT:    [[I_INITIAL:%.*]] = load volatile i32, ptr addrspace(1) [[GEP]], align 4
 ; CHECK-NEXT:    br label [[LOOP_HEADER:%.*]]
 ; CHECK:       LOOP.HEADER:
-; CHECK-NEXT:    [[I:%.*]] = phi i32 [ [[I_INITIAL]], [[ENTRY:%.*]] ], [ [[TMP5:%.*]], [[FLOW3:%.*]] ]
+; CHECK-NEXT:    [[I:%.*]] = phi i32 [ [[I_INITIAL]], [[ENTRY:%.*]] ], [ [[TMP3:%.*]], [[FLOW3:%.*]] ]
 ; CHECK-NEXT:    call void asm sideeffect "s_nop 0x100b
 ; CHECK-NEXT:    [[TMP12:%.*]] = zext i32 [[I]] to i64
 ; CHECK-NEXT:    [[TMP13:%.*]] = getelementptr inbounds <4 x i32>, ptr addrspace(1) null, i64 [[TMP12]]
@@ -49,8 +49,8 @@ define amdgpu_kernel void @loop_subregion_misordered(ptr addrspace(1) %arg0) #0
 ; CHECK-NEXT:    [[TMP25:%.*]] = mul nuw nsw i32 [[TMP24]], 52
 ; CHECK-NEXT:    br label [[INNER_LOOP:%.*]]
 ; CHECK:       Flow2:
-; CHECK-NEXT:    [[TMP3:%.*]] = phi i32 [ [[TMP59:%.*]], [[INNER_LOOP_BREAK:%.*]] ], [ [[TMP7:%.*]], [[FLOW]] ]
-; CHECK-NEXT:    [[TMP4:%.*]] = phi i1 [ true, [[INNER_LOOP_BREAK]] ], [ [[TMP9:%.*]], [[FLOW]] ]
+; CHECK-NEXT:    [[TMP3]] = phi i32 [ [[TMP59:%.*]], [[INNER_LOOP_BREAK:%.*]] ], [ [[TMP6:%.*]], [[FLOW]] ]
+; CHECK-NEXT:    [[TMP4:%.*]] = phi i1 [ true, [[INNER_LOOP_BREAK]] ], [ [[TMP8:%.*]], [[FLOW]] ]
 ; CHECK-NEXT:    br i1 [[TMP4]], label [[END_ELSE_BLOCK:%.*]], label [[FLOW3]]
 ; CHECK:       INNER_LOOP:
 ; CHECK-NEXT:    [[INNER_LOOP_J:%.*]] = phi i32 [ [[INNER_LOOP_J_INC:%.*]], [[INNER_LOOP]] ], [ [[TMP25]], [[BB18:%.*]] ]
@@ -66,20 +66,19 @@ define amdgpu_kernel void @loop_subregion_misordered(ptr addrspace(1) %arg0) #0
 ; CHECK-NEXT:    [[LOAD13:%.*]] = icmp uge i32 [[TMP16]], 271
 ; CHECK-NEXT:    br i1 [[LOAD13]], label [[INCREMENT_I]], label [[FLOW1:%.*]]
 ; CHECK:       Flow3:
-; CHECK-NEXT:    [[TMP5]] = phi i32 [ [[TMP3]], [[END_ELSE_BLOCK]] ], [ undef, [[FLOW2]] ]
-; CHECK-NEXT:    [[TMP6:%.*]] = phi i1 [ [[CMP_END_ELSE_BLOCK:%.*]], [[END_ELSE_BLOCK]] ], [ true, [[FLOW2]] ]
-; CHECK-NEXT:    br i1 [[TMP6]], label [[FLOW4:%.*]], label [[LOOP_HEADER]]
+; CHECK-NEXT:    [[TMP5:%.*]] = phi i1 [ [[CMP_END_ELSE_BLOCK:%.*]], [[END_ELSE_BLOCK]] ], [ true, [[FLOW2]] ]
+; CHECK-NEXT:    br i1 [[TMP5]], label [[FLOW4:%.*]], label [[LOOP_HEADER]]
 ; CHECK:       Flow4:
-; CHECK-NEXT:    br i1 [[TMP8:%.*]], label [[BB64:%.*]], label [[RETURN:%.*]]
+; CHECK-NEXT:    br i1 [[TMP7:%.*]], label [[BB64:%.*]], label [[RETURN:%.*]]
 ; CHECK:       bb64:
 ; CHECK-NEXT:    call void asm sideeffect "s_nop 42", "~{memory}"() #[[ATTR0]]
 ; CHECK-NEXT:    br label [[RETURN]]
 ; CHECK:       Flow:
-; CHECK-NEXT:    [[TMP7]] = phi i32 [ [[TMP0]], [[FLOW1]] ], [ undef, [[LOOP_HEADER]] ]
-; CHECK-NEXT:    [[TMP8]] = phi i1 [ [[TMP1]], [[FLOW1]] ], [ false, [[LOOP_HEADER]] ]
-; CHECK-NEXT:    [[TMP9]] = phi i1 [ [[TMP2]], [[FLOW1]] ], [ false, [[LOOP_HEADER]] ]
-; CHECK-NEXT:    [[TMP10:%.*]] = phi i1 [ false, [[FLOW1]] ], [ true, [[LOOP_HEADER]] ]
-; CHECK-NEXT:    br i1 [[TMP10]], label [[BB18]], label [[FLOW2]]
+; CHECK-NEXT:    [[TMP6]] = phi i32 [ [[TMP0]], [[FLOW1]] ], [ undef, [[LOOP_HEADER]] ]
+; CHECK-NEXT:    [[TMP7]] = phi i1 [ [[TMP1]], [[FLOW1]] ], [ false, [[LOOP_HEADER]] ]
+; CHECK-NEXT:    [[TMP8]] = phi i1 [ [[TMP2]], [[FLOW1]] ], [ false, [[LOOP_HEADER]] ]
+; CHECK-NEXT:    [[TMP9:%.*]] = phi i1 [ false, [[FLOW1]] ], [ true, [[LOOP_HEADER]] ]
+; CHECK-NEXT:    br i1 [[TMP9]], label [[BB18]], label [[FLOW2]]
 ; CHECK:       INCREMENT_I:
 ; CHECK-NEXT:    [[INC_I]] = add i32 [[I]], 1
 ; CHECK-NEXT:    call void asm sideeffect "s_nop 0x1336
diff --git a/llvm/test/Transforms/StructurizeCFG/loop-break-phi.ll b/llvm/test/Transforms/StructurizeCFG/loop-break-phi.ll
index c832b7d1394a88..46881ec8272861 100644
--- a/llvm/test/Transforms/StructurizeCFG/loop-break-phi.ll
+++ b/llvm/test/Transforms/StructurizeCFG/loop-break-phi.ll
@@ -7,8 +7,8 @@ define float @while_break(i32 %z, float %v, i32 %x, i32 %y) #0 {
 ; CHECK-NEXT:  [[ENTRY:.*]]:
 ; CHECK-NEXT:    br label %[[HEADER:.*]]
 ; CHECK:       [[HEADER]]:
-; CHECK-NEXT:    [[V_1:%.*]] = phi float [ [[V]], %[[ENTRY]] ], [ [[TMP7:%.*]], %[[FLOW2:.*]] ]
-; CHECK-NEXT:    [[IND:%.*]] = phi i32 [ 0, %[[ENTRY]] ], [ [[TMP6:%.*]], %[[FLOW2]] ]
+; CHECK-NEXT:    [[V_1:%.*]] = phi float [ [[V]], %[[ENTRY]] ], [ [[TMP8:%.*]], %[[FLOW2:.*]] ]
+; CHECK-NEXT:    [[IND:%.*]] = phi i32 [ 0, %[[ENTRY]] ], [ [[TMP5:%.*]], %[[FLOW2]] ]
 ; CHECK-NEXT:    [[CC:%.*]] = icmp sge i32 [[IND]], [[X]]
 ; CHECK-NEXT:    br i1 [[CC]], label %[[ELSE:.*]], label %[[FLOW:.*]]
 ; CHECK:       [[FLOW]]:
@@ -23,20 +23,17 @@ define float @while_break(i32 %z, float %v, i32 %x, i32 %y) #0 {
 ; CHECK-NEXT:    [[CC2]] = icmp slt i32 [[IND]], [[Y]]
 ; CHECK-NEXT:    br label %[[FLOW]]
 ; CHECK:       [[FLOW1]]:
-; CHECK-NEXT:    [[TMP3:%.*]] = phi float [ undef, %[[IF]] ], [ [[TMP0]]...
[truncated]

``````````

</details>


https://github.com/llvm/llvm-project/pull/114347


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