[llvm] r253779 - [DAGCombiner] Bugfix for lost chain depenedency.
Jonas Paulsson via llvm-commits
llvm-commits at lists.llvm.org
Sat Nov 21 05:25:08 PST 2015
Author: jonpa
Date: Sat Nov 21 07:25:07 2015
New Revision: 253779
URL: http://llvm.org/viewvc/llvm-project?rev=253779&view=rev
Log:
[DAGCombiner] Bugfix for lost chain depenedency.
When MergeConsecutiveStores() combines two loads and two stores into
wider loads and stores, the chain users of both of the original loads
must be transfered to the new load, because it may be that a chain
user only depends on one of the loads.
New test case: test/CodeGen/SystemZ/dag-combine-01.ll
Reviewed by James Y Knight.
Bugzilla: https://llvm.org/bugs/show_bug.cgi?id=25310#c6
Added:
llvm/trunk/test/CodeGen/SystemZ/dag-combine-01.ll
Modified:
llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
Modified: llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp?rev=253779&r1=253778&r2=253779&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp Sat Nov 21 07:25:07 2015
@@ -11529,7 +11529,7 @@ bool DAGCombiner::MergeConsecutiveStores
StartAddress = LoadNodes[0].OffsetFromBase;
SDValue FirstChain = FirstLoad->getChain();
for (unsigned i = 1; i < LoadNodes.size(); ++i) {
- // All loads much share the same chain.
+ // All loads must share the same chain.
if (LoadNodes[i].MemNode->getChain() != FirstChain)
break;
@@ -11621,8 +11621,8 @@ bool DAGCombiner::MergeConsecutiveStores
SDLoc LoadDL(LoadNodes[0].MemNode);
SDLoc StoreDL(StoreNodes[0].MemNode);
- // The merged loads are required to have the same chain, so using the first's
- // chain is acceptable.
+ // The merged loads are required to have the same incoming chain, so
+ // using the first's chain is acceptable.
SDValue NewLoad = DAG.getLoad(
JointMemOpVT, LoadDL, FirstLoad->getChain(), FirstLoad->getBasePtr(),
FirstLoad->getPointerInfo(), false, false, false, FirstLoadAlign);
@@ -11634,17 +11634,11 @@ bool DAGCombiner::MergeConsecutiveStores
NewStoreChain, StoreDL, NewLoad, FirstInChain->getBasePtr(),
FirstInChain->getPointerInfo(), false, false, FirstStoreAlign);
- // Replace one of the loads with the new load.
- LoadSDNode *Ld = cast<LoadSDNode>(LoadNodes[0].MemNode);
- DAG.ReplaceAllUsesOfValueWith(SDValue(Ld, 1),
- SDValue(NewLoad.getNode(), 1));
-
- // Remove the rest of the load chains.
- for (unsigned i = 1; i < NumElem ; ++i) {
- // Replace all chain users of the old load nodes with the chain of the new
- // load node.
+ // Transfer chain users from old loads to the new load.
+ for (unsigned i = 0; i < NumElem; ++i) {
LoadSDNode *Ld = cast<LoadSDNode>(LoadNodes[i].MemNode);
- DAG.ReplaceAllUsesOfValueWith(SDValue(Ld, 1), Ld->getChain());
+ DAG.ReplaceAllUsesOfValueWith(SDValue(Ld, 1),
+ SDValue(NewLoad.getNode(), 1));
}
// Replace the last store with the new store.
Added: llvm/trunk/test/CodeGen/SystemZ/dag-combine-01.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/SystemZ/dag-combine-01.ll?rev=253779&view=auto
==============================================================================
--- llvm/trunk/test/CodeGen/SystemZ/dag-combine-01.ll (added)
+++ llvm/trunk/test/CodeGen/SystemZ/dag-combine-01.ll Sat Nov 21 07:25:07 2015
@@ -0,0 +1,97 @@
+; Test that MergeConsecutiveStores() does not during DAG combining
+; incorrectly drop a chain dependency to a store previously chained to
+; one of two combined loads.
+;
+; RUN: llc < %s -mtriple=s390x-linux-gnu -mcpu=z13 | FileCheck %s
+
+ at A = common global [2048 x float] zeroinitializer, align 4
+
+; Function Attrs: nounwind
+define signext i32 @main(i32 signext %argc, i8** nocapture readnone %argv) #0 {
+entry:
+ br label %for.body
+
+for.body: ; preds = %for.body, %entry
+ %indvars.iv24 = phi i64 [ 0, %entry ], [ %indvars.iv.next25, %for.body ]
+ %sum.018 = phi float [ 0.000000e+00, %entry ], [ %add, %for.body ]
+ %0 = trunc i64 %indvars.iv24 to i32
+ %conv = sitofp i32 %0 to float
+ %arrayidx = getelementptr inbounds [2048 x float], [2048 x float]* @A, i64 0, i64 %indvars.iv24
+ store float %conv, float* %arrayidx, align 4
+ %add = fadd float %sum.018, %conv
+ %indvars.iv.next25 = add nuw nsw i64 %indvars.iv24, 1
+ %exitcond26 = icmp eq i64 %indvars.iv.next25, 2048
+ br i1 %exitcond26, label %for.end, label %for.body
+
+for.end: ; preds = %for.body
+ br label %for.body.3.lr.ph.i.preheader
+
+for.body.3.lr.ph.i.preheader: ; preds = %complex_transpose.exit, %for.end
+ %i.116 = phi i32 [ 0, %for.end ], [ %inc9, %complex_transpose.exit ]
+ br label %for.body.3.lr.ph.i
+
+for.body.3.lr.ph.i: ; preds = %for.body.3.lr.ph.i.preheader, %for.inc.40.i
+ %indvars.iv19 = phi i32 [ 1, %for.body.3.lr.ph.i.preheader ], [ %indvars.iv.next20, %for.inc.40.i ]
+ %indvars.iv57.i = phi i64 [ 1, %for.body.3.lr.ph.i.preheader ], [ %indvars.iv.next58.i, %for.inc.40.i ]
+ %1 = shl nsw i64 %indvars.iv57.i, 1
+ %2 = shl nsw i64 %indvars.iv57.i, 6
+ br label %for.body.3.i
+
+for.body.3.i: ; preds = %for.body.3.i, %for.body.3.lr.ph.i
+; CHECK-LABEL: .LBB0_5:
+; CHECK-NOT: stfh %r{{.*}}, 0(%r{{.*}})
+; CHECK: lg %r{{.*}}, -4(%r{{.*}})
+; Overlapping load should go before the store
+ %indvars.iv.i = phi i64 [ 0, %for.body.3.lr.ph.i ], [ %indvars.iv.next.i, %for.body.3.i ]
+ %3 = shl nsw i64 %indvars.iv.i, 6
+ %4 = add nuw nsw i64 %3, %1
+ %arrayidx.i = getelementptr inbounds [2048 x float], [2048 x float]* @A, i64 0, i64 %4
+ %5 = bitcast float* %arrayidx.i to i32*
+ %6 = load i32, i32* %5, align 4
+ %arrayidx9.i = getelementptr inbounds float, float* getelementptr inbounds ([2048 x float], [2048 x float]* @A, i64 0, i64 1), i64 %4
+ %7 = bitcast float* %arrayidx9.i to i32*
+ %8 = load i32, i32* %7, align 4
+ %9 = shl nsw i64 %indvars.iv.i, 1
+ %10 = add nuw nsw i64 %9, %2
+ %arrayidx14.i = getelementptr inbounds [2048 x float], [2048 x float]* @A, i64 0, i64 %10
+ %11 = bitcast float* %arrayidx14.i to i32*
+ %12 = load i32, i32* %11, align 4
+ %arrayidx19.i = getelementptr inbounds float, float* getelementptr inbounds ([2048 x float], [2048 x float]* @A, i64 0, i64 1), i64 %10
+ %13 = bitcast float* %arrayidx19.i to i32*
+ %14 = load i32, i32* %13, align 4
+ store i32 %6, i32* %11, align 4
+ store i32 %8, i32* %13, align 4
+ store i32 %12, i32* %5, align 4
+ store i32 %14, i32* %7, align 4
+ %indvars.iv.next.i = add nuw nsw i64 %indvars.iv.i, 1
+ %lftr.wideiv = trunc i64 %indvars.iv.next.i to i32
+ %exitcond21 = icmp eq i32 %lftr.wideiv, %indvars.iv19
+ br i1 %exitcond21, label %for.inc.40.i, label %for.body.3.i
+
+for.inc.40.i: ; preds = %for.body.3.i
+ %indvars.iv.next58.i = add nuw nsw i64 %indvars.iv57.i, 1
+ %indvars.iv.next20 = add nuw nsw i32 %indvars.iv19, 1
+ %exitcond22 = icmp eq i64 %indvars.iv.next58.i, 32
+ br i1 %exitcond22, label %complex_transpose.exit, label %for.body.3.lr.ph.i
+
+complex_transpose.exit: ; preds = %for.inc.40.i
+ %inc9 = add nuw nsw i32 %i.116, 1
+ %exitcond23 = icmp eq i32 %inc9, 10
+ br i1 %exitcond23, label %for.body.14.preheader, label %for.body.3.lr.ph.i.preheader
+
+for.body.14.preheader: ; preds = %complex_transpose.exit
+ br label %for.body.14
+
+for.body.14: ; preds = %for.body.14.preheader, %for.body.14
+ %indvars.iv = phi i64 [ %indvars.iv.next, %for.body.14 ], [ 0, %for.body.14.preheader ]
+ %sum.115 = phi float [ %add17, %for.body.14 ], [ 0.000000e+00, %for.body.14.preheader ]
+ %arrayidx16 = getelementptr inbounds [2048 x float], [2048 x float]* @A, i64 0, i64 %indvars.iv
+ %15 = load float, float* %arrayidx16, align 4
+ %add17 = fadd float %sum.115, %15
+ %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
+ %exitcond = icmp eq i64 %indvars.iv.next, 2048
+ br i1 %exitcond, label %for.end.20, label %for.body.14
+
+for.end.20: ; preds = %for.body.14
+ ret i32 0
+}
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