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[ValueTracking] Improve isKnownNonZero for PHI of non-zero constants

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It is clear that a PHI is a non-zero if all incoming values are non-zero constants.

llvm-svn: 259370
This commit is contained in:
Jun Bum Lim 2016-02-01 17:03:07 +00:00
parent 834c52c879
commit b95afc3d46
2 changed files with 30 additions and 0 deletions
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6
lib/Analysis/ValueTracking.cpp
View File

@ -2074,6 +2074,12 @@ bool isKnownNonZero(Value *V, unsigned Depth, const Query &Q) {
} }
} }
} }
// Check if all incoming values are non-zero constant.
bool AllNonZeroConstants = all_of(PN->operands(), [](Value *V) {
return isa<ConstantInt>(V) && !cast<ConstantInt>(V)->isZeroValue();
});
if (AllNonZeroConstants)
return true;
} }
if (!BitWidth) return false; if (!BitWidth) return false;

24
test/Transforms/InstCombine/phi.ll
View File

@ -760,3 +760,27 @@ epilog:
; CHECK-NEXT: ret i1 %[[RES]] ; CHECK-NEXT: ret i1 %[[RES]]
} }
; CHECK-LABEL: phi_allnonzeroconstant
; CHECK-NOT: phi i32
; CHECK: ret i1 false
define i1 @phi_allnonzeroconstant(i1 %c, i32 %a, i32 %b) {
entry:
br i1 %c, label %if.then, label %if.else
if.then: ; preds = %entry
br label %if.end
if.else: ; preds = %entry
call void @dummy()
br label %if.end
if.end: ; preds = %if.else, %if.then
%x.0 = phi i32 [ 1, %if.then ], [ 2, %if.else ]
%or = or i32 %x.0, %a
%cmp1 = icmp eq i32 %or, 0
ret i1 %cmp1
}
declare void @dummy()