[llvm] r257277 - [SimplifyCFG] Extend SimplifyResume to handle phi of trivial landing pad.
Chen Li via llvm-commits
llvm-commits at lists.llvm.org
Sat Jan 9 21:48:01 PST 2016
Author: chenli
Date: Sat Jan 9 23:48:01 2016
New Revision: 257277
URL: http://llvm.org/viewvc/llvm-project?rev=257277&view=rev
Log:
[SimplifyCFG] Extend SimplifyResume to handle phi of trivial landing pad.
Summary:
This is a fix of D13718. D13718 was committed but then reverted because of the following bug:
https://llvm.org/bugs/show_bug.cgi?id=25299
This patch fixes the issue shown in the bug.
Reviewers: majnemer, reames
Subscribers: jevinskie, llvm-commits
Differential Revision: http://reviews.llvm.org/D14308
Added:
llvm/trunk/test/Transforms/SimplifyCFG/bug-25299.ll
Modified:
llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp
llvm/trunk/test/Transforms/SimplifyCFG/invoke_unwind.ll
Modified: llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp?rev=257277&r1=257276&r2=257277&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp (original)
+++ llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp Sat Jan 9 23:48:01 2016
@@ -141,6 +141,8 @@ class SimplifyCFGOpt {
bool SimplifyReturn(ReturnInst *RI, IRBuilder<> &Builder);
bool SimplifyResume(ResumeInst *RI, IRBuilder<> &Builder);
+ bool SimplifySingleResume(ResumeInst *RI);
+ bool SimplifyCommonResume(ResumeInst *RI);
bool SimplifyCleanupReturn(CleanupReturnInst *RI);
bool SimplifyUnreachable(UnreachableInst *UI);
bool SimplifySwitch(SwitchInst *SI, IRBuilder<> &Builder);
@@ -3239,14 +3241,99 @@ static bool SimplifyBranchOnICmpChain(Br
}
bool SimplifyCFGOpt::SimplifyResume(ResumeInst *RI, IRBuilder<> &Builder) {
- // If this is a trivial landing pad that just continues unwinding the caught
- // exception then zap the landing pad, turning its invokes into calls.
+ if (isa<PHINode>(RI->getValue()))
+ return SimplifyCommonResume(RI);
+ else if (isa<LandingPadInst>(RI->getParent()->getFirstNonPHI()) &&
+ RI->getValue() == RI->getParent()->getFirstNonPHI())
+ // The resume must unwind the exception that caused control to branch here.
+ return SimplifySingleResume(RI);
+}
+
+// Simplify resume that is shared by several landing pads (phi of landing pad).
+bool SimplifyCFGOpt::SimplifyCommonResume(ResumeInst *RI) {
+ BasicBlock *BB = RI->getParent();
+
+ // Check that there are no other instructions except for debug intrinsics
+ // between the phi of landing pads (RI->getValue()) and resume instruction.
+ BasicBlock::iterator I = cast<Instruction>(RI->getValue())->getIterator(),
+ E = RI->getIterator();
+ while (++I != E)
+ if (!isa<DbgInfoIntrinsic>(I))
+ return false;
+
+ SmallSet<BasicBlock *, 4> TrivialUnwindBlocks;
+ auto *PhiLPInst = cast<PHINode>(RI->getValue());
+
+ // Check incoming blocks to see if any of them are trivial.
+ for (unsigned Idx = 0, End = PhiLPInst->getNumIncomingValues();
+ Idx != End; Idx++) {
+ auto *IncomingBB = PhiLPInst->getIncomingBlock(Idx);
+ auto *IncomingValue = PhiLPInst->getIncomingValue(Idx);
+
+ // If the block has other successors, we can not delete it because
+ // it has other dependents.
+ if (IncomingBB->getUniqueSuccessor() != BB)
+ continue;
+
+ auto *LandingPad =
+ dyn_cast<LandingPadInst>(IncomingBB->getFirstNonPHI());
+ // Not the landing pad that caused the control to branch here.
+ if (IncomingValue != LandingPad)
+ continue;
+
+ bool isTrivial = true;
+
+ I = IncomingBB->getFirstNonPHI()->getIterator();
+ E = IncomingBB->getTerminator()->getIterator();
+ while (++I != E)
+ if (!isa<DbgInfoIntrinsic>(I)) {
+ isTrivial = false;
+ break;
+ }
+
+ if (isTrivial)
+ TrivialUnwindBlocks.insert(IncomingBB);
+ }
+
+ // If no trivial unwind blocks, don't do any simplifications.
+ if (TrivialUnwindBlocks.empty()) return false;
+
+ // Turn all invokes that unwind here into calls.
+ for (auto *TrivialBB : TrivialUnwindBlocks) {
+ // Blocks that will be simplified should be removed from the phi node.
+ // Note there could be multiple edges to the resume block, and we need
+ // to remove them all.
+ while (PhiLPInst->getBasicBlockIndex(TrivialBB) != -1)
+ BB->removePredecessor(TrivialBB, true);
+
+ for (pred_iterator PI = pred_begin(TrivialBB), PE = pred_end(TrivialBB);
+ PI != PE;) {
+ BasicBlock *Pred = *PI++;
+ removeUnwindEdge(Pred);
+ }
+
+ // In each SimplifyCFG run, only the current processed block can be erased.
+ // Otherwise, it will break the iteration of SimplifyCFG pass. So instead
+ // of erasing TrivialBB, we only remove the branch to the common resume
+ // block so that we can later erase the resume block since it has no
+ // predecessors.
+ TrivialBB->getTerminator()->eraseFromParent();
+ new UnreachableInst(RI->getContext(), TrivialBB);
+ }
+
+ // Delete the resume block if all its predecessors have been removed.
+ if (pred_empty(BB))
+ BB->eraseFromParent();
+
+ return !TrivialUnwindBlocks.empty();
+}
+
+// Simplify resume that is only used by a single (non-phi) landing pad.
+bool SimplifyCFGOpt::SimplifySingleResume(ResumeInst *RI) {
BasicBlock *BB = RI->getParent();
LandingPadInst *LPInst = dyn_cast<LandingPadInst>(BB->getFirstNonPHI());
- if (RI->getValue() != LPInst)
- // Not a landing pad, or the resume is not unwinding the exception that
- // caused control to branch here.
- return false;
+ assert (RI->getValue() == LPInst &&
+ "Resume must unwind the exception that caused control to here");
// Check that there are no other instructions except for debug intrinsics.
BasicBlock::iterator I = LPInst->getIterator(), E = RI->getIterator();
Added: llvm/trunk/test/Transforms/SimplifyCFG/bug-25299.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/SimplifyCFG/bug-25299.ll?rev=257277&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/SimplifyCFG/bug-25299.ll (added)
+++ llvm/trunk/test/Transforms/SimplifyCFG/bug-25299.ll Sat Jan 9 23:48:01 2016
@@ -0,0 +1,40 @@
+; RUN: opt < %s -simplifycfg -S | FileCheck %s
+
+;; Test case for bug 25299, contributed by David Majnemer.
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+define void @f(i1 %B) personality i1 undef {
+entry:
+;CHECK: entry
+;CHECK-NEXT: call void @g()
+ invoke void @g()
+ to label %continue unwind label %unwind
+
+unwind: ; preds = %entry
+ %tmp101 = landingpad { i8*, i32 }
+ cleanup
+ br i1 %B, label %resume, label %then
+
+then: ; preds = %cleanup1
+ br label %resume
+
+resume: ; preds = %cleanup2, %then, %cleanup1, %unwind
+ %tmp104 = phi { i8*, i32 } [ %tmp101, %then ], [ %tmp106, %cleanup2 ], [ %tmp101, %unwind ]
+;CHECK-NOT: resume { i8*, i32 } %tmp104
+ resume { i8*, i32 } %tmp104
+
+continue: ; preds = %entry, %continue
+;CHECK: continue: ; preds = %entry, %continue
+;CHECK-NEXT: call void @g()
+ invoke void @g()
+ to label %continue unwind label %cleanup2
+
+cleanup2: ; preds = %continue
+ %tmp106 = landingpad { i8*, i32 }
+ cleanup
+ br label %resume
+}
+
+declare void @g()
\ No newline at end of file
Modified: llvm/trunk/test/Transforms/SimplifyCFG/invoke_unwind.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/SimplifyCFG/invoke_unwind.ll?rev=257277&r1=257276&r2=257277&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/SimplifyCFG/invoke_unwind.ll (original)
+++ llvm/trunk/test/Transforms/SimplifyCFG/invoke_unwind.ll Sat Jan 9 23:48:01 2016
@@ -30,4 +30,46 @@ Rethrow:
resume { i8*, i32 } %exn
}
+declare i64 @dummy1()
+declare i64 @dummy2()
+
+; This testcase checks to see if simplifycfg pass can convert two invoke
+; instructions to call instructions if they share a common trivial unwind
+; block.
+define i64 @test3(i1 %cond) personality i32 (...)* @__gxx_personality_v0 {
+entry:
+; CHECK-LABEL: @test3(
+; CHECK: %call1 = call i64 @dummy1()
+; CHECK: %call2 = call i64 @dummy2()
+; CHECK-NOT: resume { i8*, i32 } %lp
+ br i1 %cond, label %br1, label %br2
+
+br1:
+ %call1 = invoke i64 @dummy1()
+ to label %invoke.cont unwind label %lpad1
+
+br2:
+ %call2 = invoke i64 @dummy2()
+ to label %invoke.cont unwind label %lpad2
+
+invoke.cont:
+ %c = phi i64 [%call1, %br1], [%call2, %br2]
+ ret i64 %c
+
+
+lpad1:
+ %0 = landingpad { i8*, i32 }
+ cleanup
+ br label %rethrow
+
+rethrow:
+ %lp = phi { i8*, i32 } [%0, %lpad1], [%1, %lpad2]
+ resume { i8*, i32 } %lp
+
+lpad2:
+ %1 = landingpad { i8*, i32 }
+ cleanup
+ br label %rethrow
+}
+
declare i32 @__gxx_personality_v0(...)
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