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[SimplifyCFG] Do not create unneeded PR Phi in block with convergent calls 

We do not thread blocks with convergent calls, but this check was missing
when we decide to insert PR Phis into it (which we only do for threading).

Differential Revision: https://reviews.llvm.org/D83936
Reviewed By: nikic
This commit is contained in:
Max Kazantsev 2020-07-22 13:14:50 +07:00
parent c3f9697f1f
commit 360ab70712
3 changed files with 9 additions and 13 deletions
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5
clang/test/CodeGenOpenCL/convergent.cl
View File

@ -70,10 +70,9 @@ void test_merge_if(int a) {
// CHECK-NOT: call spir_func void @g()
// CHECK: br label %[[if_end]]
// CHECK: [[if_end]]:
// FIXME: SimplifyCFG is being stupid inserting this Phi. It is not supposed to be here.
// CHECK: %[[tobool_not_pr:.+]] = phi i1
// CHECK-NOT: phi i1
// CHECK: tail call spir_func void @convfun() #[[attr4:.+]]
// CHECK: br i1 %[[tobool_not_pr]], label %[[if_end3:.+]], label %[[if_then2:.+]]
// CHECK: br i1 %[[tobool]], label %[[if_end3:.+]], label %[[if_then2:.+]]
// CHECK: [[if_then2]]:
// CHECK: tail call spir_func void @g()
// CHECK: br label %[[if_end3:.+]]

13
llvm/lib/Transforms/Utils/SimplifyCFG.cpp
View File

@ -2233,6 +2233,12 @@ static bool BlockIsSimpleEnoughToThreadThrough(BasicBlock *BB) {
for (Instruction &I : BB->instructionsWithoutDebug()) {
if (Size > MaxSmallBlockSize)
return false; // Don't clone large BB's.
// Can't fold blocks that contain noduplicate or convergent calls.
if (CallInst *CI = dyn_cast<CallInst>(&I))
if (CI->cannotDuplicate() || CI->isConvergent())
return false;
// We will delete Phis while threading, so Phis should not be accounted in
// block's size
if (!isa<PHINode>(I))
@ -2274,13 +2280,6 @@ static bool FoldCondBranchOnPHI(BranchInst *BI, const DataLayout &DL,
if (!BlockIsSimpleEnoughToThreadThrough(BB))
return false;
// Can't fold blocks that contain noduplicate or convergent calls.
if (any_of(*BB, [](const Instruction &I) {
const CallInst *CI = dyn_cast<CallInst>(&I);
return CI && (CI->cannotDuplicate() || CI->isConvergent());
}))
return false;
// Okay, this is a simple enough basic block. See if any phi values are
// constants.
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {

4
llvm/test/Transforms/SimplifyCFG/convergent.ll
View File

@ -4,7 +4,6 @@
declare void @foo() convergent
; FIXME: We should not be inserting a PR Phi here.
define i32 @test_01(i32 %a) {
; CHECK-LABEL: @test_01(
; CHECK-NEXT: entry:
@ -14,9 +13,8 @@ define i32 @test_01(i32 %a) {
; CHECK-NEXT: call void @foo()
; CHECK-NEXT: br label [[MERGE]]
; CHECK: merge:
; CHECK-NEXT: [[COND_PR:%.*]] = phi i1 [ [[COND]], [[IF_FALSE]] ], [ true, [[ENTRY:%.*]] ]
; CHECK-NEXT: call void @foo()
; CHECK-NEXT: br i1 [[COND_PR]], label [[EXIT:%.*]], label [[IF_FALSE_2:%.*]]
; CHECK-NEXT: br i1 [[COND]], label [[EXIT:%.*]], label [[IF_FALSE_2:%.*]]
; CHECK: if.false.2:
; CHECK-NEXT: call void @foo()
; CHECK-NEXT: br label [[EXIT]]