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[SimplifyCFG] HoistThenElseCodeToIf(): don't hoist if either block has it's address taken

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This problem is exposed by D104598, after it tail-merges `ret` in
`@test_inline_constraint_S_label`, the verifier would start complaining
`invalid operand for inline asm constraint 'S'`.

Essentially, taking address of a block is mismodelled in IR.
It should probably be an explicit instruction, a first one in block,
that isn't identical to any other instruction of the same type,
so that it can't be hoisted.
This commit is contained in:
Roman Lebedev 2021-06-20 12:18:15 +03:00
parent b719c3f4a5
commit 9120098319
3 changed files with 40 additions and 0 deletions
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6
lib/Transforms/Utils/SimplifyCFG.cpp
View File

@ -1404,6 +1404,12 @@ bool SimplifyCFGOpt::HoistThenElseCodeToIf(BranchInst *BI,
BasicBlock *BB1 = BI->getSuccessor(0); // The true destination.
BasicBlock *BB2 = BI->getSuccessor(1); // The false destination
// If either of the blocks has it's address taken, then we can't do this fold,
// because the code we'd hoist would no longer run when we jump into the block
// by it's address.
if (BB1->hasAddressTaken() || BB2->hasAddressTaken())
return false;
BasicBlock::iterator BB1_Itr = BB1->begin();
BasicBlock::iterator BB2_Itr = BB2->begin();

13
test/CodeGen/AArch64/inlineasm-S-constraint.ll
View File

@ -18,3 +18,16 @@ loc:
loc2:
ret i32 42
}
define i32 @test_inline_constraint_S_label_tailmerged(i1 %in) {
; CHECK-LABEL: test_inline_constraint_S_label_tailmerged:
call void asm sideeffect "adr x0, $0", "S"(i8* blockaddress(@test_inline_constraint_S_label_tailmerged, %loc))
; CHECK: adr x0, .Ltmp{{[0-9]+}}
br i1 %in, label %loc, label %loc2
loc:
br label %common.ret
loc2:
br label %common.ret
common.ret:
%common.retval = phi i32 [ 0, %loc ], [ 42, %loc2 ]
ret i32 %common.retval
}

21
test/Transforms/SimplifyCFG/hoist-from-addresstaken-block.ll Normal file
View File

@ -0,0 +1,21 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt < %s -mem2reg -simplifycfg -simplifycfg-require-and-preserve-domtree=1 -S | FileCheck %s
define i32 @test_inline_constraint_S_label_tailmerged(i1 %in) {
; CHECK-LABEL: @test_inline_constraint_S_label_tailmerged(
; CHECK-NEXT: call void asm sideeffect "adr x0, $0", "S"(i8* blockaddress(@test_inline_constraint_S_label_tailmerged, [[COMMON_RET:%.*]]))
; CHECK-NEXT: [[COMMON_RETVAL:%.*]] = select i1 [[IN:%.*]], i32 0, i32 42
; CHECK-NEXT: br label [[COMMON_RET]]
; CHECK: common.ret:
; CHECK-NEXT: ret i32 [[COMMON_RETVAL]]
;
call void asm sideeffect "adr x0, $0", "S"(i8* blockaddress(@test_inline_constraint_S_label_tailmerged, %loc))
br i1 %in, label %loc, label %loc2
loc:
br label %common.ret
loc2:
br label %common.ret
common.ret:
%common.retval = phi i32 [ 0, %loc ], [ 42, %loc2 ]
ret i32 %common.retval
}