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Revert "[ValueTracking] Teach computeKnownBits for PHI nodes to compute sign bit for a recurrence with a NSW addition."

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This is breaking an optimizaton remark test in clang. I've identified a couple fixes for that, but want to understand it better before I commit to anything.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@274102 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Craig Topper 2016-06-29 04:57:00 +00:00
parent 6818d39eeb
commit c590a00f89
3 changed files with 1 additions and 128 deletions
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12
lib/Analysis/ValueTracking.cpp
View File

@ -1240,18 +1240,6 @@ static void computeKnownBitsFromOperator(Operator *I, APInt &KnownZero,
KnownZero = APInt::getLowBitsSet(BitWidth,
std::min(KnownZero2.countTrailingOnes(),
KnownZero3.countTrailingOnes()));
// If the operation is an addition that can't have signed overflow,
// then the sign bit is known to be zero if both input sign bits
// are zero. Similar for two negative inputs.
if (Opcode == Instruction::Add &&
cast<OverflowingBinaryOperator>(LU)->hasNoSignedWrap()) {
if (KnownZero2.isNegative() && KnownZero3.isNegative())
KnownZero.setBit(BitWidth-1);
if (KnownOne2.isNegative() && KnownOne3.isNegative())
KnownOne.setBit(BitWidth-1);
}
break;
}
}

2
test/Transforms/BBVectorize/loop1.ll
View File

@ -83,7 +83,7 @@ for.body: ; preds = %for.body, %entry
; CHECK-UNRL: %add12 = fadd <2 x double> %add7, %mul11
; CHECK-UNRL: %4 = bitcast double* %arrayidx14 to <2 x double>*
; CHECK-UNRL: store <2 x double> %add12, <2 x double>* %4, align 8
; CHECK-UNRL: %indvars.iv.next.1 = add nuw nsw i64 %indvars.iv, 2
; CHECK-UNRL: %indvars.iv.next.1 = add nsw i64 %indvars.iv, 2
; CHECK-UNRL: %lftr.wideiv.1 = trunc i64 %indvars.iv.next.1 to i32
; CHECK-UNRL: %exitcond.1 = icmp eq i32 %lftr.wideiv.1, 10
; CHECK-UNRL: br i1 %exitcond.1, label %for.end, label %for.body

115
test/Transforms/InstCombine/phi.ll
View File

@ -879,118 +879,3 @@ if.end: ; preds = %entry, %if.then
%cmp1 = icmp ne i32 %a.0, 0
ret i1 %cmp1
}
; This test makes sure we can determine that the inputs to the sdiv in the loop
; are non-negative and can become a udiv. This requires that we recognize that
; the loop induction can never have its sign bit set.
;
; CHECK-LABEL: @phi_nsw_induction_sdiv_udiv
; CHECK: udiv
; CHECK: udiv
define i32 @phi_nsw_induction_sdiv_udiv(i32 %NumElts, i32 %ScalarSize) {
entry:
%div = udiv i32 128, %ScalarSize
br label %for.cond
for.cond: ; preds = %for.inc, %entry
%Sum.0 = phi i32 [ 0, %entry ], [ %add, %for.inc ]
%i.0 = phi i32 [ 0, %entry ], [ %inc, %for.inc ]
%cmp = icmp ne i32 %i.0, %NumElts
br i1 %cmp, label %for.body, label %for.end
for.body: ; preds = %for.cond
; this should become a udiv
%div1 = sdiv i32 %i.0, %div
%add = add nsw i32 %Sum.0, %div1
br label %for.inc
for.inc: ; preds = %for.body
%inc = add nsw i32 %i.0, 1
br label %for.cond
for.end: ; preds = %for.cond
ret i32 %Sum.0
}
; CHECK-LABEL: test_positive_nsw_recurrence
; CHECK-NOT: bar
; CHECK: foo
; CHECK-NOT: bar
; CHECK: ret
define void @test_positive_nsw_recurrence(i32 %N) {
entry:
br label %for.cond
for.cond: ; preds = %for.inc, %entry
%i.0 = phi i32 [ 0, %entry ], [ %inc, %for.inc ]
%cmp = icmp ne i32 %i.0, %N
br i1 %cmp, label %for.body, label %for.end
for.body: ; preds = %for.cond
%and = and i32 %i.0, -2147483648
%tobool = icmp ne i32 %and, 0
br i1 %tobool, label %if.then, label %if.else
if.then: ; preds = %for.body
; this call should be deleted as %i.0 can never be negative due to no signed wrap
call void @bar()
br label %if.end
if.else: ; preds = %for.body
call void @foo()
br label %if.end
if.end: ; preds = %if.else, %if.then
br label %for.inc
for.inc: ; preds = %if.end
%inc = add nsw i32 %i.0, 1
br label %for.cond
for.end: ; preds = %for.cond
ret void
}
; CHECK-LABEL: test_negative_nsw_recurrence
; CHECK-NOT: foo
; CHECK: bar
; CHECK-NOT: foo
; CHECK: ret
define void @test_negative_nsw_recurrence(i32 %N) {
entry:
br label %for.cond
for.cond: ; preds = %for.inc, %entry
%i.0 = phi i32 [ -1, %entry ], [ %inc, %for.inc ]
%cmp = icmp ne i32 %i.0, %N
br i1 %cmp, label %for.body, label %for.end
for.body: ; preds = %for.cond
%and = and i32 %i.0, -2147483648
%tobool = icmp ne i32 %and, 0
br i1 %tobool, label %if.then, label %if.else
if.then: ; preds = %for.body
call void @bar()
br label %if.end
if.else: ; preds = %for.body
; this call should be deleted as %i.0 can never be positive due to no signed wrap
call void @foo()
br label %if.end
if.end: ; preds = %if.else, %if.then
br label %for.inc
for.inc: ; preds = %if.end
%inc = add nsw i32 %i.0, -1
br label %for.cond
for.end: ; preds = %for.cond
ret void
}
declare void @bar()
declare void @foo()