[llvm] ed0fd56 - BreakCriticalEdges: do not split the critical edge from a CallBr indirect successor
Nick Desaulniers via llvm-commits
llvm-commits at lists.llvm.org
Fri Jan 15 13:52:06 PST 2021
Author: Nick Desaulniers
Date: 2021-01-15T13:51:47-08:00
New Revision: ed0fd567ebdbbbbc61eb87346a58196a73f9b814
URL: https://github.com/llvm/llvm-project/commit/ed0fd567ebdbbbbc61eb87346a58196a73f9b814
DIFF: https://github.com/llvm/llvm-project/commit/ed0fd567ebdbbbbc61eb87346a58196a73f9b814.diff
LOG: BreakCriticalEdges: do not split the critical edge from a CallBr indirect successor
Otherwise we'll fail the assertion in SplitBlockPredecessors() related
to splitting the edges from CallBr's.
Fixes: https://github.com/ClangBuiltLinux/linux/issues/1161
Fixes: https://github.com/ClangBuiltLinux/linux/issues/1252
Reviewed By: void, MaskRay, jyknight
Differential Revision: https://reviews.llvm.org/D88438
Added:
llvm/test/Transforms/LoopStrengthReduce/callbr-critical-edge-splitting.ll
llvm/test/Transforms/LoopStrengthReduce/callbr-critical-edge-splitting2.ll
Modified:
llvm/lib/Transforms/Utils/BreakCriticalEdges.cpp
Removed:
################################################################################
diff --git a/llvm/lib/Transforms/Utils/BreakCriticalEdges.cpp b/llvm/lib/Transforms/Utils/BreakCriticalEdges.cpp
index c9f08e5a9ed5..939a1a3a868d 100644
--- a/llvm/lib/Transforms/Utils/BreakCriticalEdges.cpp
+++ b/llvm/lib/Transforms/Utils/BreakCriticalEdges.cpp
@@ -158,22 +158,21 @@ BasicBlock *llvm::SplitCriticalEdge(Instruction *TI, unsigned SuccNum,
SmallVector<BasicBlock *, 4> LoopPreds;
// Check if extra modifications will be required to preserve loop-simplify
// form after splitting. If it would require splitting blocks with IndirectBr
- // terminators, bail out if preserving loop-simplify form is requested.
+ // or CallBr terminators, bail out if preserving loop-simplify form is
+ // requested.
if (LI) {
if (Loop *TIL = LI->getLoopFor(TIBB)) {
- // The only that we can break LoopSimplify form by splitting a critical
- // edge is if after the split there exists some edge from TIL to DestBB
- // *and* the only edge into DestBB from outside of TIL is that of
+ // The only way that we can break LoopSimplify form by splitting a
+ // critical edge is if after the split there exists some edge from TIL to
+ // DestBB *and* the only edge into DestBB from outside of TIL is that of
// NewBB. If the first isn't true, then LoopSimplify still holds, NewBB
// is the new exit block and it has no non-loop predecessors. If the
// second isn't true, then DestBB was not in LoopSimplify form prior to
// the split as it had a non-loop predecessor. In both of these cases,
// the predecessor must be directly in TIL, not in a subloop, or again
// LoopSimplify doesn't hold.
- for (pred_iterator I = pred_begin(DestBB), E = pred_end(DestBB); I != E;
- ++I) {
- BasicBlock *P = *I;
+ for (BasicBlock *P : predecessors(DestBB)) {
if (P == TIBB)
continue; // The new block is known.
if (LI->getLoopFor(P) != TIL) {
@@ -186,7 +185,10 @@ BasicBlock *llvm::SplitCriticalEdge(Instruction *TI, unsigned SuccNum,
// Loop-simplify form can be preserved, if we can split all in-loop
// predecessors.
if (any_of(LoopPreds, [](BasicBlock *Pred) {
- return isa<IndirectBrInst>(Pred->getTerminator());
+ const Instruction *T = Pred->getTerminator();
+ if (const auto *CBR = dyn_cast<CallBrInst>(T))
+ return CBR->getDefaultDest() != Pred;
+ return isa<IndirectBrInst>(T);
})) {
if (Options.PreserveLoopSimplify)
return nullptr;
diff --git a/llvm/test/Transforms/LoopStrengthReduce/callbr-critical-edge-splitting.ll b/llvm/test/Transforms/LoopStrengthReduce/callbr-critical-edge-splitting.ll
new file mode 100644
index 000000000000..8c62e9cf5caa
--- /dev/null
+++ b/llvm/test/Transforms/LoopStrengthReduce/callbr-critical-edge-splitting.ll
@@ -0,0 +1,39 @@
+; RUN: opt -loop-reduce %s -o - -S | FileCheck %s
+; RUN: opt -passes='loop(loop-reduce)' %s -o - -S | FileCheck %s
+
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
+
+define dso_local i32 @test1() local_unnamed_addr {
+entry:
+ br label %for.cond
+
+for.cond: ; preds = %for.inc, %entry
+; It's ok to modify this test in the future should be able to split critical
+; edges here, just noting that this is the critical edge that we care about.
+; CHECK: callbr void asm sideeffect "", "X,X,~{dirflag},~{fpsr},~{flags}"(i8* blockaddress(@test1, %cond.true.i), i8* blockaddress(@test1, %for.end))
+; CHECK-NEXT: to label %asm.fallthrough.i.i [label %cond.true.i, label %for.end]
+ callbr void asm sideeffect "", "X,X,~{dirflag},~{fpsr},~{flags}"(i8* blockaddress(@test1, %cond.true.i), i8* blockaddress(@test1, %for.end))
+ to label %asm.fallthrough.i.i [label %cond.true.i, label %for.end]
+
+asm.fallthrough.i.i: ; preds = %for.cond
+ unreachable
+
+cond.true.i: ; preds = %for.cond
+ br label %do.body.i.i.do.body.i.i_crit_edge
+
+do.body.i.i.do.body.i.i_crit_edge: ; preds = %do.body.i.i.do.body.i.i_crit_edge, %cond.true.i
+ %pgocount711 = phi i64 [ %0, %do.body.i.i.do.body.i.i_crit_edge ], [ 0, %cond.true.i ]
+ %0 = add nuw nsw i64 %pgocount711, 1
+ br i1 undef, label %do.body.i.i.rdrand_int.exit.i_crit_edge, label %do.body.i.i.do.body.i.i_crit_edge
+
+do.body.i.i.rdrand_int.exit.i_crit_edge: ; preds = %do.body.i.i.do.body.i.i_crit_edge
+ %1 = add i64 %0, undef
+ br i1 undef, label %for.end, label %for.inc
+
+for.inc: ; preds = %do.body.i.i.rdrand_int.exit.i_crit_edge
+ br label %for.cond
+
+for.end: ; preds = %do.body.i.i.rdrand_int.exit.i_crit_edge, %for.cond
+ %pgocount.promoted24 = phi i64 [ undef, %for.cond ], [ %1, %do.body.i.i.rdrand_int.exit.i_crit_edge ]
+ ret i32 undef
+}
diff --git a/llvm/test/Transforms/LoopStrengthReduce/callbr-critical-edge-splitting2.ll b/llvm/test/Transforms/LoopStrengthReduce/callbr-critical-edge-splitting2.ll
new file mode 100644
index 000000000000..6df251cd10bb
--- /dev/null
+++ b/llvm/test/Transforms/LoopStrengthReduce/callbr-critical-edge-splitting2.ll
@@ -0,0 +1,61 @@
+; RUN: opt -passes='loop(loop-reduce)' %s -o - -S | FileCheck %s
+
+; Required metadata to trigger previously failing assertion.
+target datalayout = "e-m:e-i64:64-n32:64"
+
+ at f = external dso_local local_unnamed_addr global i32, align 4
+
+declare i32 @a() local_unnamed_addr
+declare i32 @e(i32) local_unnamed_addr
+
+define dso_local i32 @b() {
+entry:
+ %call = tail call i32 @a()
+ %tobool.not = icmp eq i32 %call, 0
+ br i1 %tobool.not, label %cleanup.cont.critedge, label %if.then
+
+if.then: ; preds = %entry
+; It's ok to modify this test in the future should be able to split critical
+; edges here, just noting that this is the critical edge that we care about.
+; CHECK: callbr void asm sideeffect "", "X"(i8* blockaddress(@b, %cleanup.cont.critedge))
+; CHECK-NEXT: to label %return [label %cleanup.cont.critedge]
+ callbr void asm sideeffect "", "X"(i8* blockaddress(@b, %cleanup.cont.critedge))
+ to label %return [label %cleanup.cont.critedge]
+
+cleanup.cont.critedge: ; preds = %entry, %if.then
+ br label %return
+
+return: ; preds = %if.then, %cleanup.cont.critedge
+ %retval.0 = phi i32 [ 4, %cleanup.cont.critedge ], [ 0, %if.then ]
+ ret i32 %retval.0
+}
+
+define dso_local i32 @do_pages_move_nr_pages() local_unnamed_addr {
+entry:
+ br label %for.cond
+
+for.cond: ; preds = %if.end3, %entry
+ %g.0 = phi i32 [ undef, %entry ], [ %inc, %if.end3 ]
+ %0 = load i32, i32* @f, align 4
+ %tobool.not = icmp eq i32 %0, 0
+ br i1 %tobool.not, label %if.end3, label %if.then
+
+if.then: ; preds = %for.cond
+ %call.i = tail call i32 @a()
+ %tobool.not.i = icmp eq i32 %call.i, 0
+ br i1 %tobool.not.i, label %if.then2, label %if.then.i
+
+if.then.i: ; preds = %if.then
+ callbr void asm sideeffect "", "X"(i8* blockaddress(@do_pages_move_nr_pages, %if.then2))
+ to label %if.end3 [label %if.then2]
+
+if.then2: ; preds = %if.then, %if.then.i
+ %g.0.lcssa = phi i32 [ %g.0, %if.then ], [ %g.0, %if.then.i ]
+ %call4 = tail call i32 @e(i32 %g.0.lcssa)
+ ret i32 undef
+
+if.end3: ; preds = %for.cond, %if.then.i
+ %inc = add nsw i32 %g.0, 1
+ br label %for.cond
+}
+
More information about the llvm-commits
mailing list