[llvm] r354159 - [CodeExtractor] Do not lift lifetime.end markers for region inputs
Vedant Kumar via llvm-commits
llvm-commits at lists.llvm.org
Fri Feb 15 10:46:58 PST 2019
Author: vedantk
Date: Fri Feb 15 10:46:58 2019
New Revision: 354159
URL: http://llvm.org/viewvc/llvm-project?rev=354159&view=rev
Log:
[CodeExtractor] Do not lift lifetime.end markers for region inputs
If a lifetime.end marker occurs along one path through the extraction
region, but not another, then it's still incorrect to lift the marker,
because there is some path through the extracted function which would
ordinarily not reach the marker. If the call to the extracted function
is in a loop, unrolling can cause inputs to the function to become
optimized out as undef after the first iteration.
To prevent incorrect stack slot merging in the calling function, it
should be sufficient to lift lifetime.start markers for region inputs.
I've tested this theory out by doing a stage2 check-all with randomized
splitting enabled.
This is a follow-up to r353973, and there's additional context for this
change in https://reviews.llvm.org/D57834.
rdar://47896986
Differential Revision: https://reviews.llvm.org/D58253
Modified:
llvm/trunk/lib/Transforms/Utils/CodeExtractor.cpp
llvm/trunk/test/Transforms/CodeExtractor/PartialInlineAlloca4.ll
llvm/trunk/test/Transforms/HotColdSplit/lifetime-markers-on-inputs-1.ll
llvm/trunk/test/Transforms/HotColdSplit/lifetime-markers-on-inputs-2.ll
Modified: llvm/trunk/lib/Transforms/Utils/CodeExtractor.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/CodeExtractor.cpp?rev=354159&r1=354158&r2=354159&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Utils/CodeExtractor.cpp (original)
+++ llvm/trunk/lib/Transforms/Utils/CodeExtractor.cpp Fri Feb 15 10:46:58 2019
@@ -886,16 +886,14 @@ Function *CodeExtractor::constructFuncti
}
/// Erase lifetime.start markers which reference inputs to the extraction
-/// region, and insert the referenced memory into \p LifetimesStart. Do the same
-/// with lifetime.end markers (but insert them into \p LifetimesEnd).
+/// region, and insert the referenced memory into \p LifetimesStart.
///
/// The extraction region is defined by a set of blocks (\p Blocks), and a set
/// of allocas which will be moved from the caller function into the extracted
/// function (\p SunkAllocas).
static void eraseLifetimeMarkersOnInputs(const SetVector<BasicBlock *> &Blocks,
const SetVector<Value *> &SunkAllocas,
- SetVector<Value *> &LifetimesStart,
- SetVector<Value *> &LifetimesEnd) {
+ SetVector<Value *> &LifetimesStart) {
for (BasicBlock *BB : Blocks) {
for (auto It = BB->begin(), End = BB->end(); It != End;) {
auto *II = dyn_cast<IntrinsicInst>(&*It);
@@ -912,8 +910,6 @@ static void eraseLifetimeMarkersOnInputs
if (II->getIntrinsicID() == Intrinsic::lifetime_start)
LifetimesStart.insert(Mem);
- else
- LifetimesEnd.insert(Mem);
II->eraseFromParent();
}
}
@@ -1421,12 +1417,11 @@ Function *CodeExtractor::extractCodeRegi
}
// Collect objects which are inputs to the extraction region and also
- // referenced by lifetime start/end markers within it. The effects of these
+ // referenced by lifetime start markers within it. The effects of these
// markers must be replicated in the calling function to prevent the stack
// coloring pass from merging slots which store input objects.
- ValueSet LifetimesStart, LifetimesEnd;
- eraseLifetimeMarkersOnInputs(Blocks, SinkingCands, LifetimesStart,
- LifetimesEnd);
+ ValueSet LifetimesStart;
+ eraseLifetimeMarkersOnInputs(Blocks, SinkingCands, LifetimesStart);
// Construct new function based on inputs/outputs & add allocas for all defs.
Function *newFunction =
@@ -1449,9 +1444,8 @@ Function *CodeExtractor::extractCodeRegi
// Replicate the effects of any lifetime start/end markers which referenced
// input objects in the extraction region by placing markers around the call.
- insertLifetimeMarkersSurroundingCall(oldFunction->getParent(),
- LifetimesStart.getArrayRef(),
- LifetimesEnd.getArrayRef(), TheCall);
+ insertLifetimeMarkersSurroundingCall(
+ oldFunction->getParent(), LifetimesStart.getArrayRef(), {}, TheCall);
// Propagate personality info to the new function if there is one.
if (oldFunction->hasPersonalityFn())
Modified: llvm/trunk/test/Transforms/CodeExtractor/PartialInlineAlloca4.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/CodeExtractor/PartialInlineAlloca4.ll?rev=354159&r1=354158&r2=354159&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/CodeExtractor/PartialInlineAlloca4.ll (original)
+++ llvm/trunk/test/Transforms/CodeExtractor/PartialInlineAlloca4.ll Fri Feb 15 10:46:58 2019
@@ -9,7 +9,6 @@
; CHECK-LABEL: define{{.*}}@caller(
; CHECK: call void @llvm.lifetime.start.p0i8(i64 -1, i8* %tmp.i)
; CHECK-NEXT: call void @callee_unknown_use1.{{.*}}(i8* %tmp.i
-; CHECK-NEXT: call void @llvm.lifetime.end.p0i8(i64 -1, i8* %tmp.i)
define i32 @callee_unknown_use1(i32 %arg) local_unnamed_addr #0 {
; CHECK-LABEL:define{{.*}}@callee_unknown_use1.{{[0-9]}}
Modified: llvm/trunk/test/Transforms/HotColdSplit/lifetime-markers-on-inputs-1.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/HotColdSplit/lifetime-markers-on-inputs-1.ll?rev=354159&r1=354158&r2=354159&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/HotColdSplit/lifetime-markers-on-inputs-1.ll (original)
+++ llvm/trunk/test/Transforms/HotColdSplit/lifetime-markers-on-inputs-1.ll Fri Feb 15 10:46:58 2019
@@ -34,8 +34,6 @@ normalPath:
; CHECK-NEXT: [[local2_cast:%.*]] = bitcast i256* %local2 to i8*
; CHECK-NEXT: call void @llvm.lifetime.start.p0i8(i64 -1, i8* [[local2_cast]])
; CHECK-NEXT: call i1 @foo.cold.1(i8* %local1_cast, i8* %local2_cast)
-; CHECK-NEXT: call void @llvm.lifetime.end.p0i8(i64 -1, i8* [[local1_cast]])
-; CHECK-NEXT: call void @llvm.lifetime.end.p0i8(i64 -1, i8* [[local2_cast]])
; CHECK-NEXT: br i1
outlinedPath:
Modified: llvm/trunk/test/Transforms/HotColdSplit/lifetime-markers-on-inputs-2.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/HotColdSplit/lifetime-markers-on-inputs-2.ll?rev=354159&r1=354158&r2=354159&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/HotColdSplit/lifetime-markers-on-inputs-2.ll (original)
+++ llvm/trunk/test/Transforms/HotColdSplit/lifetime-markers-on-inputs-2.ll Fri Feb 15 10:46:58 2019
@@ -7,6 +7,8 @@ declare void @llvm.lifetime.end.p0i8(i64
declare void @cold_use(i8*) cold
+declare void @use(i8*)
+
; In this CFG, splitting will extract the blocks extract{1,2}. I.e., it will
; extract a lifetime.start marker, but not the corresponding lifetime.end
; marker. Make sure that a lifetime.start marker is emitted before the call to
@@ -73,9 +75,8 @@ exit:
}
; In this CFG, splitting will extract the block extract1. I.e., it will extract
-; a lifetime.end marker, but not the corresponding lifetime.start marker. Make
-; sure that a lifetime.end marker is emitted after the call to the split
-; function, and *only* that marker.
+; a lifetime.end marker, but not the corresponding lifetime.start marker. Do
+; not emit a lifetime.end marker after the call to the split function.
;
; entry
; (lt.start)
@@ -91,7 +92,7 @@ exit:
; (lt.start)
; / \
; no-extract1 codeRepl
-; (lt.end) (lt.end)
+; (lt.end)
; \ /
; exit
define void @only_lifetime_end_is_cold() {
@@ -105,9 +106,7 @@ define void @only_lifetime_end_is_cold()
; CHECK-NEXT: call void @llvm.lifetime.end.p0i8(i64 1, i8* [[LOCAL1_CAST]])
; CHECK-NEXT: br label [[EXIT:%.*]]
; CHECK: codeRepl:
-; CHECK-NEXT: [[LT_CAST:%.*]] = bitcast i256* [[LOCAL1]] to i8*
; CHECK-NEXT: call void @only_lifetime_end_is_cold.cold.1(i8* [[LOCAL1_CAST]]) #3
-; CHECK-NEXT: call void @llvm.lifetime.end.p0i8(i64 -1, i8* [[LT_CAST]])
; CHECK-NEXT: br label [[EXIT]]
; CHECK: exit:
; CHECK-NEXT: ret void
@@ -130,6 +129,54 @@ extract1:
call void @llvm.lifetime.end.p0i8(i64 1, i8* %local1_cast)
br label %exit
+exit:
+ ret void
+}
+
+; In this CFG, splitting will extract the blocks extract{1,2,3}. Lifting the
+; lifetime.end marker would be a miscompile.
+define void @do_not_lift_lifetime_end() {
+; CHECK-LABEL: @do_not_lift_lifetime_end(
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[LOCAL1:%.*]] = alloca i256
+; CHECK-NEXT: [[LOCAL1_CAST:%.*]] = bitcast i256* [[LOCAL1]] to i8*
+; CHECK-NEXT: call void @llvm.lifetime.start.p0i8(i64 1, i8* [[LOCAL1_CAST]])
+; CHECK-NEXT: br label [[HEADER:%.*]]
+; CHECK: header:
+; CHECK-NEXT: call void @use(i8* [[LOCAL1_CAST]])
+; CHECK-NEXT: br i1 undef, label [[EXIT:%.*]], label [[CODEREPL:%.*]]
+; CHECK: codeRepl:
+; CHECK-NEXT: [[TARGETBLOCK:%.*]] = call i1 @do_not_lift_lifetime_end.cold.1(i8* [[LOCAL1_CAST]]) #3
+; CHECK-NEXT: br i1 [[TARGETBLOCK]], label [[HEADER]], label [[EXIT]]
+; CHECK: exit:
+; CHECK-NEXT: ret void
+;
+entry:
+ ; lt.start
+ %local1 = alloca i256
+ %local1_cast = bitcast i256* %local1 to i8*
+ call void @llvm.lifetime.start.p0i8(i64 1, i8* %local1_cast)
+ br label %header
+
+header:
+ ; If the lifetime.end marker is lifted, this use becomes dead the second time
+ ; the header block is executed.
+ call void @use(i8* %local1_cast)
+ br i1 undef, label %exit, label %extract1
+
+extract1:
+ call void @cold_use(i8* %local1_cast)
+ br i1 undef, label %extract2, label %extract3
+
+extract2:
+ ; Backedge.
+ br label %header
+
+extract3:
+ ; lt.end
+ call void @llvm.lifetime.end.p0i8(i64 1, i8* %local1_cast)
+ br label %exit
+
exit:
ret void
}
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