[llvm] 8b7c3d2 - [LV] Set SCEVCheckCond to nullptr whenever it was used.
Florian Hahn via llvm-commits
llvm-commits at lists.llvm.org
Sun May 15 13:52:17 PDT 2022
Author: Florian Hahn
Date: 2022-05-15T21:52:07+01:00
New Revision: 8b7c3d2179b3c0dadb957ff255d7bdf3283474a8
URL: https://github.com/llvm/llvm-project/commit/8b7c3d2179b3c0dadb957ff255d7bdf3283474a8
DIFF: https://github.com/llvm/llvm-project/commit/8b7c3d2179b3c0dadb957ff255d7bdf3283474a8.diff
LOG: [LV] Set SCEVCheckCond to nullptr whenever it was used.
Under some circumstances, SCEVExpander will insert new instructions when
expanding a predicate, but the final result of the expansion can be a
false constant.
In those cases, the expanded instructions may later be used by other
expansions, e.g. the trip count. This may trigger an assertion during
SCEVExpander cleanup. To avoid this, always mark the result as used.
Fixes #55100.
Added:
llvm/test/Transforms/LoopVectorize/pr55100-expand-scev-predicate-used.ll
Modified:
llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
Removed:
################################################################################
diff --git a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
index b74e65f8266c8..3501920430e11 100644
--- a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -2072,7 +2072,11 @@ class GeneratedRTChecks {
BasicBlock *LoopExitBlock) {
if (!SCEVCheckCond)
return nullptr;
- if (auto *C = dyn_cast<ConstantInt>(SCEVCheckCond))
+
+ Value *Cond = SCEVCheckCond;
+ // Mark the check as used, to prevent it from being removed during cleanup.
+ SCEVCheckCond = nullptr;
+ if (auto *C = dyn_cast<ConstantInt>(Cond))
if (C->isZero())
return nullptr;
@@ -2091,11 +2095,8 @@ class GeneratedRTChecks {
DT->addNewBlock(SCEVCheckBlock, Pred);
DT->changeImmediateDominator(LoopVectorPreHeader, SCEVCheckBlock);
- ReplaceInstWithInst(
- SCEVCheckBlock->getTerminator(),
- BranchInst::Create(Bypass, LoopVectorPreHeader, SCEVCheckCond));
- // Mark the check as used, to prevent it from being removed during cleanup.
- SCEVCheckCond = nullptr;
+ ReplaceInstWithInst(SCEVCheckBlock->getTerminator(),
+ BranchInst::Create(Bypass, LoopVectorPreHeader, Cond));
return SCEVCheckBlock;
}
diff --git a/llvm/test/Transforms/LoopVectorize/pr55100-expand-scev-predicate-used.ll b/llvm/test/Transforms/LoopVectorize/pr55100-expand-scev-predicate-used.ll
new file mode 100644
index 0000000000000..82173685e48d9
--- /dev/null
+++ b/llvm/test/Transforms/LoopVectorize/pr55100-expand-scev-predicate-used.ll
@@ -0,0 +1,96 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -passes='loop-vectorize' -force-vector-width=2 -force-vector-interleave=1 -S %s | FileCheck %s
+
+define void @test_pr55100(i32 %N) {
+; CHECK-LABEL: @test_pr55100(
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[TMP0:%.*]] = sub i32 0, [[N:%.*]]
+; CHECK-NEXT: br label [[LOOP_1_HEADER:%.*]]
+; CHECK: loop.1.header:
+; CHECK-NEXT: [[IV_1:%.*]] = phi i32 [ 0, [[ENTRY:%.*]] ], [ [[IV_1_NEXT:%.*]], [[LOOP_1_LATCH:%.*]] ]
+; CHECK-NEXT: [[TMP1:%.*]] = mul nuw nsw i32 [[IV_1]], -1
+; CHECK-NEXT: [[TMP2:%.*]] = add i32 [[TMP0]], [[TMP1]]
+; CHECK-NEXT: [[UMIN2:%.*]] = call i32 @llvm.umin.i32(i32 [[TMP2]], i32 18)
+; CHECK-NEXT: [[TMP3:%.*]] = add nuw nsw i32 [[UMIN2]], 1
+; CHECK-NEXT: [[TMP4:%.*]] = mul nuw nsw i32 [[IV_1]], -1
+; CHECK-NEXT: [[TMP5:%.*]] = add i32 [[TMP0]], [[TMP4]]
+; CHECK-NEXT: [[UMIN:%.*]] = call i32 @llvm.umin.i32(i32 [[TMP5]], i32 18)
+; CHECK-NEXT: [[C_2:%.*]] = icmp ugt i32 [[IV_1]], 10
+; CHECK-NEXT: br i1 [[C_2]], label [[LOOP_2_HEADER_PREHEADER:%.*]], label [[EXIT_LOOPEXIT1:%.*]]
+; CHECK: loop.2.header.preheader:
+; CHECK-NEXT: [[MIN_ITERS_CHECK:%.*]] = icmp ule i32 [[TMP3]], 2
+; CHECK-NEXT: br i1 [[MIN_ITERS_CHECK]], label [[SCALAR_PH:%.*]], label [[VECTOR_PH:%.*]]
+; CHECK: vector.ph:
+; CHECK-NEXT: [[N_MOD_VF:%.*]] = urem i32 [[TMP3]], 2
+; CHECK-NEXT: [[TMP6:%.*]] = icmp eq i32 [[N_MOD_VF]], 0
+; CHECK-NEXT: [[TMP7:%.*]] = select i1 [[TMP6]], i32 2, i32 [[N_MOD_VF]]
+; CHECK-NEXT: [[N_VEC:%.*]] = sub i32 [[TMP3]], [[TMP7]]
+; CHECK-NEXT: [[IND_END:%.*]] = trunc i32 [[N_VEC]] to i16
+; CHECK-NEXT: br label [[VECTOR_BODY:%.*]]
+; CHECK: vector.body:
+; CHECK-NEXT: [[INDEX:%.*]] = phi i32 [ 0, [[VECTOR_PH]] ], [ [[INDEX_NEXT:%.*]], [[VECTOR_BODY]] ]
+; CHECK-NEXT: [[OFFSET_IDX:%.*]] = trunc i32 [[INDEX]] to i16
+; CHECK-NEXT: [[TMP8:%.*]] = add i16 [[OFFSET_IDX]], 0
+; CHECK-NEXT: [[TMP9:%.*]] = add i32 [[N]], [[IV_1]]
+; CHECK-NEXT: [[TMP10:%.*]] = sext i16 [[TMP8]] to i32
+; CHECK-NEXT: [[TMP11:%.*]] = add i32 [[TMP9]], [[TMP10]]
+; CHECK-NEXT: [[INDEX_NEXT]] = add nuw i32 [[INDEX]], 2
+; CHECK-NEXT: [[TMP12:%.*]] = icmp eq i32 [[INDEX_NEXT]], [[N_VEC]]
+; CHECK-NEXT: br i1 [[TMP12]], label [[MIDDLE_BLOCK:%.*]], label [[VECTOR_BODY]], !llvm.loop [[LOOP0:![0-9]+]]
+; CHECK: middle.block:
+; CHECK-NEXT: br label [[SCALAR_PH]]
+; CHECK: scalar.ph:
+; CHECK-NEXT: [[BC_RESUME_VAL:%.*]] = phi i16 [ [[IND_END]], [[MIDDLE_BLOCK]] ], [ 0, [[LOOP_2_HEADER_PREHEADER]] ]
+; CHECK-NEXT: br label [[LOOP_2_HEADER:%.*]]
+; CHECK: vector.scevcheck:
+; CHECK-NEXT: [[TMP13:%.*]] = trunc i32 [[UMIN]] to i16
+; CHECK-NEXT: unreachable
+; CHECK: loop.2.header:
+; CHECK-NEXT: [[IV_2:%.*]] = phi i16 [ [[IV_2_NEXT:%.*]], [[LOOP_2_LATCH:%.*]] ], [ [[BC_RESUME_VAL]], [[SCALAR_PH]] ]
+; CHECK-NEXT: [[C_3:%.*]] = icmp slt i16 [[IV_2]], 18
+; CHECK-NEXT: br i1 [[C_3]], label [[LOOP_2_LATCH]], label [[LOOP_1_LATCH]]
+; CHECK: loop.2.latch:
+; CHECK-NEXT: [[ADD_1:%.*]] = add i32 [[N]], [[IV_1]]
+; CHECK-NEXT: [[IV_2_EXT:%.*]] = sext i16 [[IV_2]] to i32
+; CHECK-NEXT: [[ADD_2:%.*]] = add i32 [[ADD_1]], [[IV_2_EXT]]
+; CHECK-NEXT: [[C_4:%.*]] = icmp ult i32 [[ADD_2]], 1
+; CHECK-NEXT: [[IV_2_NEXT]] = add i16 [[IV_2]], 1
+; CHECK-NEXT: br i1 [[C_4]], label [[EXIT_LOOPEXIT:%.*]], label [[LOOP_2_HEADER]], !llvm.loop [[LOOP2:![0-9]+]]
+; CHECK: loop.1.latch:
+; CHECK-NEXT: [[IV_1_NEXT]] = add i32 [[IV_1]], 1
+; CHECK-NEXT: br label [[LOOP_1_HEADER]]
+; CHECK: exit.loopexit:
+; CHECK-NEXT: br label [[EXIT:%.*]]
+; CHECK: exit.loopexit1:
+; CHECK-NEXT: br label [[EXIT]]
+; CHECK: exit:
+; CHECK-NEXT: ret void
+;
+entry:
+ br label %loop.1.header
+
+loop.1.header:
+ %iv.1 = phi i32 [ 0, %entry ], [ %iv.1.next, %loop.1.latch ]
+ %c.2 = icmp ugt i32 %iv.1, 10
+ br i1 %c.2, label %loop.2.header, label %exit
+
+loop.2.header:
+ %iv.2 = phi i16 [ 0, %loop.1.header ], [ %iv.2.next, %loop.2.latch ]
+ %c.3 = icmp slt i16 %iv.2, 18
+ br i1 %c.3, label %loop.2.latch, label %loop.1.latch
+
+loop.2.latch:
+ %add.1 = add i32 %N, %iv.1
+ %iv.2.ext = sext i16 %iv.2 to i32
+ %add.2 = add i32 %add.1, %iv.2.ext
+ %c.4 = icmp ult i32 %add.2, 1
+ %iv.2.next = add i16 %iv.2, 1
+ br i1 %c.4, label %exit, label %loop.2.header
+
+loop.1.latch:
+ %iv.1.next = add i32 %iv.1, 1
+ br label %loop.1.header
+
+exit:
+ ret void
+}
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