[SimplifyCFG] Don't sink loads/stores with swifterror pointers.

[fhahn]

Summary

swifterror pointers can only be used as pointer operands of load & store
instructions (and as swifterror argument of a call). Sinking loads or
stores with swifterror pointer operands would require introducing a
select of of the pointer operands, which isn't allowed.

Check for this condition in canSinkInstructions.

[aschwaighofer]

lgtm

llvm/lib/Transforms/Utils/SimplifyCFG.cpp

for (auto *I : Insts) {
     // Each instruction must have zero or one use.
     if (HasUse && !I->hasOneUse())
       return false;
     if (!HasUse && !I->user_empty())
       return false;
   }
 
   const Instruction *I0 = Insts.front();
-  for (auto *I : Insts)
+  for (auto *I : Insts) {
     if (!I->isSameOperationAs(I0))
       return false;
 
+    // swifterror pointers can only be used by a load or store; sinking a load
+    // or store would require introducing a select for the pointer operand,
+    // which isn't allowed for swifterror pointers.
+    if (isa<StoreInst>(I) && I->getOperand(1)->isSwiftError())
+      return false;
+    if (isa<LoadInst>(I) && I->getOperand(0)->isSwiftError())
+      return false;
+  }
+
   // All instructions in Insts are known to be the same opcode. If they have a
   // use, check that the only user is a PHI or in the same block as the
   // instruction, because if a user is in the same block as an instruction we're
   // contemplating sinking, it must already be determined to be sinkable.
   if (HasUse) {
     auto *PNUse = dyn_cast<PHINode>(*I0->user_begin());
     auto *Succ = I0->getParent()->getTerminator()->getSuccessor(0);
     if (!all_of(Insts, [&PNUse,&Succ](const Instruction *I) -> bool {

llvm/test/Transforms/SimplifyCFG/hoist-sink-swifterror-store.ll

-; RUN: opt -passes='simplifycfg<sink-common-insts;hoist-common-insts>,verify' -disable-output %s
-
-; XFAIL: *
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 2
+; RUN: opt -passes='simplifycfg<sink-common-insts;hoist-common-insts>,verify' -S %s | FileCheck %s
 
 declare void @clobber1()
 declare void @clobber2()
 
-; FIXME: currently simplifycfg tries to sink the stores to the exit block and
-; introduces a select for the pointer operand. This is not allowed for
-; swifterror pointers.
-define swiftcc void @sink_store(ptr %arg, ptr swifterror %arg1, i1 %c) {
+; Do not try to sink the stores to the exit block, as this requires introducing
+; a select for the pointer operand. This is not allowed for swifterror pointers.
+define swiftcc void @sink(ptr %arg, ptr swifterror %arg1, i1 %c) {
+; CHECK-LABEL: define swiftcc void @sink
+; CHECK-SAME: (ptr [[ARG:%.*]], ptr swifterror [[ARG1:%.*]], i1 [[C:%.*]]) {
+; CHECK-NEXT:  bb:
+; CHECK-NEXT:    br i1 [[C]], label [[THEN:%.*]], label [[ELSE:%.*]]
+; CHECK:       then:
+; CHECK-NEXT:    call void @clobber1()
+; CHECK-NEXT:    store ptr null, ptr [[ARG]], align 8
+; CHECK-NEXT:    br label [[EXIT:%.*]]
+; CHECK:       else:
+; CHECK-NEXT:    call void @clobber2()
+; CHECK-NEXT:    store ptr null, ptr [[ARG1]], align 8
+; CHECK-NEXT:    br label [[EXIT]]
+; CHECK:       exit:
+; CHECK-NEXT:    ret void
+;
 bb:
   br i1 %c, label %then, label %else
 
 then:
   call void @clobber1()
   store ptr null, ptr %arg, align 8
   br label %exit
 
 else:
   call void @clobber2()
   store ptr null, ptr %arg1, align 8
   br label %exit
 
 exit:
   ret void
 }
 
 define swiftcc void @hoist_store(ptr %arg, ptr swifterror %arg1, i1 %c) {
+; CHECK-LABEL: define swiftcc void @hoist_store
+; CHECK-SAME: (ptr [[ARG:%.*]], ptr swifterror [[ARG1:%.*]], i1 [[C:%.*]]) {
+; CHECK-NEXT:  bb:
+; CHECK-NEXT:    br i1 [[C]], label [[THEN:%.*]], label [[ELSE:%.*]]
+; CHECK:       then:
+; CHECK-NEXT:    store ptr null, ptr [[ARG]], align 8
+; CHECK-NEXT:    call void @clobber1()
+; CHECK-NEXT:    br label [[EXIT:%.*]]
+; CHECK:       else:
+; CHECK-NEXT:    store ptr null, ptr [[ARG1]], align 8
+; CHECK-NEXT:    call void @clobber2()
+; CHECK-NEXT:    br label [[EXIT]]
+; CHECK:       exit:
+; CHECK-NEXT:    ret void
+;
 bb:
   br i1 %c, label %then, label %else
 
 then:
   store ptr null, ptr %arg, align 8
   call void @clobber1()
   br label %exit
 
else:
   %l2 = load ptr, ptr %arg1, align 8
   br label %exit
 
 exit:
   %p = phi ptr [ %l1, %then ], [ %l2, %else ]
   ret ptr %p
 }
 define swiftcc ptr @hoist_load(ptr %arg, ptr swifterror %arg1, i1 %c) {
+; CHECK-LABEL: define swiftcc ptr @hoist_load
+; CHECK-SAME: (ptr [[ARG:%.*]], ptr swifterror [[ARG1:%.*]], i1 [[C:%.*]]) {
+; CHECK-NEXT:  bb:
+; CHECK-NEXT:    br i1 [[C]], label [[THEN:%.*]], label [[ELSE:%.*]]
+; CHECK:       then:
+; CHECK-NEXT:    [[L1:%.*]] = load ptr, ptr [[ARG]], align 8
+; CHECK-NEXT:    call void @clobber1()
+; CHECK-NEXT:    br label [[EXIT:%.*]]
+; CHECK:       else:
+; CHECK-NEXT:    [[L2:%.*]] = load ptr, ptr [[ARG1]], align 8
+; CHECK-NEXT:    call void @clobber2()
+; CHECK-NEXT:    br label [[EXIT]]
+; CHECK:       exit:
+; CHECK-NEXT:    [[P:%.*]] = phi ptr [ [[L1]], [[THEN]] ], [ [[L2]], [[ELSE]] ]
+; CHECK-NEXT:    ret ptr [[P]]
+;
 bb:
   br i1 %c, label %then, label %else
 
 then:
   %l1 = load ptr, ptr %arg, align 8
   call void @clobber1()
   br label %exit