[llvm] 662bede - [LV] Handle known-false mem runtime checks in GeneratedRTChecks.

[Florian Hahn via llvm-commits]

Author: Florian Hahn
Date: 2025-07-26T15:39:21+01:00
New Revision: 662bede01e6d8515a1a2c3eb125c322711f23037

URL: https://github.com/llvm/llvm-project/commit/662bede01e6d8515a1a2c3eb125c322711f23037
DIFF: https://github.com/llvm/llvm-project/commit/662bede01e6d8515a1a2c3eb125c322711f23037.diff

LOG: [LV] Handle known-false mem runtime checks in GeneratedRTChecks.

Handle mem checks known to be false in getMemRuntimeChecks the same way
as SCEV checks known to be false in getSCEVChecks. This ensures such
redundant check blocks are not added in the first place.

Added: 
    

Modified: 
    llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
    llvm/test/Transforms/LoopVectorize/runtime-check-known-true.ll

Removed: 
    


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diff  --git a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
index a9cb55b995b09..79d6edd857765 100644
--- a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -2021,6 +2021,9 @@ class GeneratedRTChecks {
   /// Retrieves the MemCheckCond and MemCheckBlock that were generated as IR
   /// outside VPlan.
   std::pair<Value *, BasicBlock *> getMemRuntimeChecks() {
+    using namespace llvm::PatternMatch;
+    if (MemRuntimeCheckCond && match(MemRuntimeCheckCond, m_ZeroInt()))
+      return {nullptr, nullptr};
     return {MemRuntimeCheckCond, MemCheckBlock};
   }
 

diff  --git a/llvm/test/Transforms/LoopVectorize/runtime-check-known-true.ll b/llvm/test/Transforms/LoopVectorize/runtime-check-known-true.ll
index fabd1d4d15f29..830bd92c70b16 100644
--- a/llvm/test/Transforms/LoopVectorize/runtime-check-known-true.ll
+++ b/llvm/test/Transforms/LoopVectorize/runtime-check-known-true.ll
@@ -24,9 +24,7 @@ define void @test_runtime_check_known_false_after_construction(ptr %start.1, ptr
 ; CHECK-NEXT:    [[TMP7:%.*]] = sub i3 [[TMP5]], [[TMP6]]
 ; CHECK-NEXT:    [[TMP8:%.*]] = zext i3 [[TMP7]] to i64
 ; CHECK-NEXT:    [[IDENT_CHECK:%.*]] = icmp ne i64 [[TMP8]], 0
-; CHECK-NEXT:    br i1 [[IDENT_CHECK]], label %[[SCALAR_PH]], label %[[VECTOR_MEMCHECK:.*]]
-; CHECK:       [[VECTOR_MEMCHECK]]:
-; CHECK-NEXT:    br i1 false, label %[[SCALAR_PH]], label %[[VECTOR_PH:.*]]
+; CHECK-NEXT:    br i1 [[IDENT_CHECK]], label %[[SCALAR_PH]], label %[[VECTOR_PH:.*]]
 ; CHECK:       [[VECTOR_PH]]:
 ; CHECK-NEXT:    [[N_MOD_VF:%.*]] = urem i64 [[TMP4]], 4
 ; CHECK-NEXT:    [[N_VEC:%.*]] = sub i64 [[TMP4]], [[N_MOD_VF]]
@@ -56,8 +54,8 @@ define void @test_runtime_check_known_false_after_construction(ptr %start.1, ptr
 ; CHECK-NEXT:    [[CMP_N:%.*]] = icmp eq i64 [[TMP4]], [[N_VEC]]
 ; CHECK-NEXT:    br i1 [[CMP_N]], label %[[EXIT:.*]], label %[[SCALAR_PH]]
 ; CHECK:       [[SCALAR_PH]]:
-; CHECK-NEXT:    [[BC_RESUME_VAL:%.*]] = phi ptr [ [[TMP10]], %[[MIDDLE_BLOCK]] ], [ [[START_1]], %[[ENTRY]] ], [ [[START_1]], %[[VECTOR_SCEVCHECK]] ], [ [[START_1]], %[[VECTOR_MEMCHECK]] ]
-; CHECK-NEXT:    [[BC_RESUME_VAL5:%.*]] = phi ptr [ [[TMP12]], %[[MIDDLE_BLOCK]] ], [ [[START_2_DIFF]], %[[ENTRY]] ], [ [[START_2_DIFF]], %[[VECTOR_SCEVCHECK]] ], [ [[START_2_DIFF]], %[[VECTOR_MEMCHECK]] ]
+; CHECK-NEXT:    [[BC_RESUME_VAL:%.*]] = phi ptr [ [[TMP10]], %[[MIDDLE_BLOCK]] ], [ [[START_1]], %[[ENTRY]] ], [ [[START_1]], %[[VECTOR_SCEVCHECK]] ]
+; CHECK-NEXT:    [[BC_RESUME_VAL5:%.*]] = phi ptr [ [[TMP12]], %[[MIDDLE_BLOCK]] ], [ [[START_2_DIFF]], %[[ENTRY]] ], [ [[START_2_DIFF]], %[[VECTOR_SCEVCHECK]] ]
 ; CHECK-NEXT:    br label %[[LOOP:.*]]
 ; CHECK:       [[LOOP]]:
 ; CHECK-NEXT:    [[PTR_IV_1:%.*]] = phi ptr [ [[PTR_IV_1_NEXT:%.*]], %[[LOOP]] ], [ [[BC_RESUME_VAL]], %[[SCALAR_PH]] ]