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[WideableCond] Fix a nasty bug in detection of "explicit guards"

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The code was failing to actually check for the presence of the call to widenable_condition.  The whole point of specifying the widenable_condition intrinsic was allowing widening transforms.  A normal branch is not widenable.  A normal branch leading to a deopt is not widenable (in general).

I added a test case via LoopPredication, but GuardWidening has an analogous bug.  Those are the only two passes actually using this utility just yet. Noticed while working on LoopPredication for non-widenable branches; POC in D60111.

llvm-svn: 357493
This commit is contained in:
Philip Reames 2019-04-02 16:51:43 +00:00
parent 5f836d34ef
commit 07eb26281f
2 changed files with 66 additions and 2 deletions
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9
lib/Analysis/GuardUtils.cpp
View File

@ -39,6 +39,11 @@ bool llvm::parseWidenableBranch(const User *U, Value *&Condition,
Value *&WidenableCondition,
BasicBlock *&IfTrueBB, BasicBlock *&IfFalseBB) {
using namespace llvm::PatternMatch;
return match(U, m_Br(m_And(m_Value(Condition), m_Value(WidenableCondition)),
IfTrueBB, IfFalseBB));
if (!match(U, m_Br(m_And(m_Value(Condition), m_Value(WidenableCondition)),
IfTrueBB, IfFalseBB)))
return false;
// TODO: At the moment, we only recognize the branch if the WC call in this
// specific position. We should generalize!
return match(WidenableCondition,
m_Intrinsic<Intrinsic::experimental_widenable_condition>());
}

59
test/Transforms/LoopPredication/basic_widenable_branch_guards.ll
View File

@ -1863,6 +1863,65 @@ exit: ; preds = %guarded, %entry
ret i32 %result
}
; Make sure that if we're going to consider a branch widenable, that the
; call to widenable condition is actually present.
define i32 @negative_WC_required(i32* %array, i32 %length, i32 %n, i1 %unrelated) {
; CHECK-LABEL: @negative_WC_required(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[TMP5:%.*]] = icmp eq i32 [[N:%.*]], 0
; CHECK-NEXT: br i1 [[TMP5]], label [[EXIT:%.*]], label [[LOOP_PREHEADER:%.*]]
; CHECK: loop.preheader:
; CHECK-NEXT: br label [[LOOP:%.*]]
; CHECK: loop:
; CHECK-NEXT: [[I:%.*]] = phi i32 [ [[I_NEXT:%.*]], [[GUARDED:%.*]] ], [ 0, [[LOOP_PREHEADER]] ]
; CHECK-NEXT: [[WITHIN_BOUNDS:%.*]] = icmp ult i32 [[I]], [[LENGTH:%.*]]
; CHECK-NEXT: [[NOT_WIDENABLE:%.*]] = and i1 [[WITHIN_BOUNDS]], [[UNRELATED:%.*]]
; CHECK-NEXT: br i1 [[NOT_WIDENABLE]], label [[GUARDED]], label [[DEOPT:%.*]], !prof !0
; CHECK: deopt:
; CHECK-NEXT: [[DEOPTCALL:%.*]] = call i32 (...) @llvm.experimental.deoptimize.i32(i32 9) [ "deopt"() ]
; CHECK-NEXT: ret i32 [[DEOPTCALL]]
; CHECK: guarded:
; CHECK-NEXT: [[I_I64:%.*]] = zext i32 [[I]] to i64
; CHECK-NEXT: [[ARRAY_I_PTR:%.*]] = getelementptr inbounds i32, i32* [[ARRAY:%.*]], i64 [[I_I64]]
; CHECK-NEXT: store i32 0, i32* [[ARRAY_I_PTR]], align 4
; CHECK-NEXT: [[I_NEXT]] = add nuw i32 [[I]], 1
; CHECK-NEXT: [[CONTINUE:%.*]] = icmp ult i32 [[I_NEXT]], [[N]]
; CHECK-NEXT: br i1 [[CONTINUE]], label [[LOOP]], label [[EXIT_LOOPEXIT:%.*]]
; CHECK: exit.loopexit:
; CHECK-NEXT: br label [[EXIT]]
; CHECK: exit:
; CHECK-NEXT: ret i32 0
;
entry:
%tmp5 = icmp eq i32 %n, 0
br i1 %tmp5, label %exit, label %loop.preheader
loop.preheader: ; preds = %entry
br label %loop
loop:
%i = phi i32 [ %i.next, %guarded ], [ 0, %loop.preheader ]
%within.bounds = icmp ult i32 %i, %length
%not_widenable = and i1 %within.bounds, %unrelated
br i1 %not_widenable, label %guarded, label %deopt, !prof !0
deopt:
%deoptcall = call i32 (...) @llvm.experimental.deoptimize.i32(i32 9) [ "deopt"() ]
ret i32 %deoptcall
guarded: ; preds = %loop
%i.i64 = zext i32 %i to i64
%array.i.ptr = getelementptr inbounds i32, i32* %array, i64 %i.i64
store i32 0, i32* %array.i.ptr, align 4
%i.next = add nuw i32 %i, 1
%continue = icmp ult i32 %i.next, %n
br i1 %continue, label %loop, label %exit
exit: ; preds = %guarded, %entry
ret i32 0
}
declare i32 @llvm.experimental.deoptimize.i32(...)
; Function Attrs: inaccessiblememonly nounwind