[llvm] b21fa18 - [LoopVersioning] Add a check to see if the input loop is in LCSSA form (#116443)
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Mon Dec 16 08:55:23 PST 2024
Author: Vedant Paranjape
Date: 2024-12-16T11:55:19-05:00
New Revision: b21fa18b44dd73284bd1c6551b8046c94f84f9f3
URL: https://github.com/llvm/llvm-project/commit/b21fa18b44dd73284bd1c6551b8046c94f84f9f3
DIFF: https://github.com/llvm/llvm-project/commit/b21fa18b44dd73284bd1c6551b8046c94f84f9f3.diff
LOG: [LoopVersioning] Add a check to see if the input loop is in LCSSA form (#116443)
Loop Optimizations expect the input loop to be in LCSSA form. But it
seems that LoopVersioning doesn't have any check to see if the loop is
actually in LCSSA form. As a result, if we give it a loop which is not
in LCSSA form but still correct semantically, the resulting
transformation fails to pass through verifier pass with the following
error.
Instruction does not dominate all uses!
%inc = add nsw i16 undef, 1
store i16 %inc, ptr @c, align 1
As the loop is not in LCSSA form, LoopVersioning's transformations leads
to invalid IR! As some instructions do not dominate all their uses.
This patch checks if a loop is in LCSSA form, if not it will call
formLCSSARecursively on the loop before passing it to LoopVersioning.
Fixes: #36998
Added:
llvm/test/Transforms/LoopVersioning/crash-36998.ll
Modified:
llvm/lib/Transforms/Utils/LoopVersioning.cpp
Removed:
################################################################################
diff --git a/llvm/lib/Transforms/Utils/LoopVersioning.cpp b/llvm/lib/Transforms/Utils/LoopVersioning.cpp
index 8f8c40a4e73be1..5ee551e6f0ccbd 100644
--- a/llvm/lib/Transforms/Utils/LoopVersioning.cpp
+++ b/llvm/lib/Transforms/Utils/LoopVersioning.cpp
@@ -26,6 +26,7 @@
#include "llvm/Support/CommandLine.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/Cloning.h"
+#include "llvm/Transforms/Utils/LoopUtils.h"
#include "llvm/Transforms/Utils/ScalarEvolutionExpander.h"
using namespace llvm;
@@ -278,6 +279,9 @@ bool runImpl(LoopInfo *LI, LoopAccessInfoManager &LAIs, DominatorTree *DT,
if (!LAI.hasConvergentOp() &&
(LAI.getNumRuntimePointerChecks() ||
!LAI.getPSE().getPredicate().isAlwaysTrue())) {
+ if (!L->isLCSSAForm(*DT))
+ formLCSSARecursively(*L, *DT, LI, SE);
+
LoopVersioning LVer(LAI, LAI.getRuntimePointerChecking()->getChecks(), L,
LI, DT, SE);
LVer.versionLoop();
diff --git a/llvm/test/Transforms/LoopVersioning/crash-36998.ll b/llvm/test/Transforms/LoopVersioning/crash-36998.ll
new file mode 100644
index 00000000000000..1217d9405e9f89
--- /dev/null
+++ b/llvm/test/Transforms/LoopVersioning/crash-36998.ll
@@ -0,0 +1,64 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; RUN: opt -passes=loop-versioning -aa-pipeline='' -S < %s | FileCheck %s
+
+ at a = external global i16, align 1
+ at b = external global i16, align 1
+ at c = external global i16, align 1
+
+define i16 @f2(i16 %a) {
+; CHECK-LABEL: define i16 @f2(
+; CHECK-SAME: i16 [[A:%.*]]) {
+; CHECK-NEXT: [[FOR_BODY_LVER_CHECK:.*:]]
+; CHECK-NEXT: [[BOUND0:%.*]] = icmp ult ptr @b, getelementptr inbounds nuw (i8, ptr @a, i64 2)
+; CHECK-NEXT: [[BOUND1:%.*]] = icmp ult ptr @a, getelementptr inbounds nuw (i8, ptr @b, i64 2)
+; CHECK-NEXT: [[FOUND_CONFLICT:%.*]] = and i1 [[BOUND0]], [[BOUND1]]
+; CHECK-NEXT: br i1 [[FOUND_CONFLICT]], label %[[FOR_BODY_PH_LVER_ORIG:.*]], label %[[FOR_BODY_PH:.*]]
+; CHECK: [[FOR_BODY_PH_LVER_ORIG]]:
+; CHECK-NEXT: br label %[[FOR_BODY_LVER_ORIG:.*]]
+; CHECK: [[FOR_BODY_LVER_ORIG]]:
+; CHECK-NEXT: [[TMP0:%.*]] = load i16, ptr @a, align 1
+; CHECK-NEXT: store i16 [[TMP0]], ptr @b, align 1
+; CHECK-NEXT: [[INC_LVER_ORIG:%.*]] = add nsw i16 [[A]], 1
+; CHECK-NEXT: br i1 false, label %[[FOR_BODY_LVER_ORIG]], label %[[FOR_COND_FOR_END_CRIT_EDGE_LOOPEXIT:.*]]
+; CHECK: [[FOR_BODY_PH]]:
+; CHECK-NEXT: br label %[[FOR_BODY:.*]]
+; CHECK: [[FOR_BODY]]:
+; CHECK-NEXT: [[TMP1:%.*]] = load i16, ptr @a, align 1, !alias.scope [[META0:![0-9]+]]
+; CHECK-NEXT: store i16 [[TMP1]], ptr @b, align 1, !alias.scope [[META3:![0-9]+]], !noalias [[META0]]
+; CHECK-NEXT: [[INC:%.*]] = add nsw i16 [[A]], 1
+; CHECK-NEXT: br i1 false, label %[[FOR_BODY]], label %[[FOR_COND_FOR_END_CRIT_EDGE_LOOPEXIT1:.*]]
+; CHECK: [[FOR_COND_FOR_END_CRIT_EDGE_LOOPEXIT]]:
+; CHECK-NEXT: [[INC_LCSSA_PH:%.*]] = phi i16 [ [[INC_LVER_ORIG]], %[[FOR_BODY_LVER_ORIG]] ]
+; CHECK-NEXT: [[SPLIT2_PH:%.*]] = phi i16 [ [[INC_LVER_ORIG]], %[[FOR_BODY_LVER_ORIG]] ]
+; CHECK-NEXT: br label %[[FOR_COND_FOR_END_CRIT_EDGE:.*]]
+; CHECK: [[FOR_COND_FOR_END_CRIT_EDGE_LOOPEXIT1]]:
+; CHECK-NEXT: [[INC_LCSSA_PH2:%.*]] = phi i16 [ [[INC]], %[[FOR_BODY]] ]
+; CHECK-NEXT: [[SPLIT2_PH3:%.*]] = phi i16 [ [[INC]], %[[FOR_BODY]] ]
+; CHECK-NEXT: br label %[[FOR_COND_FOR_END_CRIT_EDGE]]
+; CHECK: [[FOR_COND_FOR_END_CRIT_EDGE]]:
+; CHECK-NEXT: [[INC_LCSSA:%.*]] = phi i16 [ [[INC_LCSSA_PH]], %[[FOR_COND_FOR_END_CRIT_EDGE_LOOPEXIT]] ], [ [[INC_LCSSA_PH2]], %[[FOR_COND_FOR_END_CRIT_EDGE_LOOPEXIT1]] ]
+; CHECK-NEXT: [[SPLIT2:%.*]] = phi i16 [ [[SPLIT2_PH]], %[[FOR_COND_FOR_END_CRIT_EDGE_LOOPEXIT]] ], [ [[SPLIT2_PH3]], %[[FOR_COND_FOR_END_CRIT_EDGE_LOOPEXIT1]] ]
+; CHECK-NEXT: store i16 [[INC_LCSSA]], ptr @c, align 1
+; CHECK-NEXT: ret i16 [[SPLIT2]]
+;
+entry:
+ br label %for.body
+
+for.body: ; preds = %for.body, %entry
+ %0 = load i16, ptr @a, align 1
+ store i16 %0, ptr @b, align 1
+ %inc = add nsw i16 %a, 1
+ br i1 false, label %for.body, label %for.cond.for.end_crit_edge
+
+for.cond.for.end_crit_edge: ; preds = %for.body
+ %split2 = phi i16 [ %inc, %for.body ]
+ store i16 %inc, ptr @c, align 1
+ ret i16 %split2
+}
+;.
+; CHECK: [[META0]] = !{[[META1:![0-9]+]]}
+; CHECK: [[META1]] = distinct !{[[META1]], [[META2:![0-9]+]]}
+; CHECK: [[META2]] = distinct !{[[META2]], !"LVerDomain"}
+; CHECK: [[META3]] = !{[[META4:![0-9]+]]}
+; CHECK: [[META4]] = distinct !{[[META4]], [[META2]]}
+;.
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