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[SimplifyCFG] Tail-merging all blocks with `resume` terminator 

Similar to what we already do for `ret` terminators.
As noted by @rnk, clang seems to already generate a single `ret`/`resume`,
so this isn't likely to cause widespread changes.

Reviewed By: rnk

Differential Revision: https://reviews.llvm.org/D104849
This commit is contained in:
Roman Lebedev 2021-06-24 21:25:06 +03:00
parent 46afddec41
commit d064182612
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GPG Key ID: 083C3EBB4A1689E0
2 changed files with 15 additions and 9 deletions
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9
llvm/lib/Transforms/Scalar/SimplifyCFGPass.cpp
View File

@ -94,10 +94,15 @@ static bool tailMergeBlocksWithSimilarFunctionTerminators(Function &F,
auto *Term = BB.getTerminator(); auto *Term = BB.getTerminator();
// Fow now only support `ret` function terminators. // Fow now only support `ret`/`resume` function terminators.
// FIXME: lift this restriction. // FIXME: lift this restriction.
if (Term->getOpcode() != Instruction::Ret) switch (Term->getOpcode()) {
case Instruction::Ret:
case Instruction::Resume:
break;
default:
continue; continue;
}
// We can't tail-merge block that contains a musttail call. // We can't tail-merge block that contains a musttail call.
if (BB.getTerminatingMustTailCall()) if (BB.getTerminatingMustTailCall())

15
llvm/test/Transforms/SimplifyCFG/tail-merge-resume.ll
View File

@ -39,19 +39,20 @@ define void @merge_simple(i1 %cond) personality i8* bitcast (i32 (...)* @__gxx_p
; CHECK-NEXT: cleanup ; CHECK-NEXT: cleanup
; CHECK-NEXT: call void @baz() ; CHECK-NEXT: call void @baz()
; CHECK-NEXT: br label [[RESUME2]] ; CHECK-NEXT: br label [[RESUME2]]
; CHECK: common.resume:
; CHECK-NEXT: [[COMMON_RESUME_OP:%.*]] = phi { i8*, i32 } [ [[LP]], [[RESUME0]] ], [ [[LP]], [[RESUME1]] ], [ [[SEMICOMMON_LP:%.*]], [[RESUME2]] ]
; CHECK-NEXT: call void @common()
; CHECK-NEXT: resume { i8*, i32 } [[COMMON_RESUME_OP]]
; CHECK: resume0: ; CHECK: resume0:
; CHECK-NEXT: call void @qux() ; CHECK-NEXT: call void @qux()
; CHECK-NEXT: call void @common() ; CHECK-NEXT: br label [[COMMON_RESUME:%.*]]
; CHECK-NEXT: resume { i8*, i32 } [[LP]]
; CHECK: resume1: ; CHECK: resume1:
; CHECK-NEXT: call void @quux() ; CHECK-NEXT: call void @quux()
; CHECK-NEXT: call void @common() ; CHECK-NEXT: br label [[COMMON_RESUME]]
; CHECK-NEXT: resume { i8*, i32 } [[LP]]
; CHECK: resume2: ; CHECK: resume2:
; CHECK-NEXT: [[SEMICOMMON_LP:%.*]] = phi { i8*, i32 } [ [[LP2]], [[LPAD2]] ], [ [[LP3]], [[LPAD3]] ] ; CHECK-NEXT: [[SEMICOMMON_LP]] = phi { i8*, i32 } [ [[LP2]], [[LPAD2]] ], [ [[LP3]], [[LPAD3]] ]
; CHECK-NEXT: call void @quuz() ; CHECK-NEXT: call void @quuz()
; CHECK-NEXT: call void @common() ; CHECK-NEXT: br label [[COMMON_RESUME]]
; CHECK-NEXT: resume { i8*, i32 } [[SEMICOMMON_LP]]
; ;
invoke void @maybe_throws() to label %invoke.cont unwind label %lpad invoke void @maybe_throws() to label %invoke.cont unwind label %lpad