[llvm] r292239 - [ValueTracking] recognize a 'not' of an assumed condition as false
Sanjay Patel via llvm-commits
llvm-commits at lists.llvm.org
Tue Jan 17 10:15:50 PST 2017
Author: spatel
Date: Tue Jan 17 12:15:49 2017
New Revision: 292239
URL: http://llvm.org/viewvc/llvm-project?rev=292239&view=rev
Log:
[ValueTracking] recognize a 'not' of an assumed condition as false
Also, add the corresponding match to the AssumptionCache's 'Affected Values' list.
Differential Revision: https://reviews.llvm.org/D28485
Modified:
llvm/trunk/lib/Analysis/AssumptionCache.cpp
llvm/trunk/lib/Analysis/ValueTracking.cpp
llvm/trunk/test/Transforms/InstCombine/assume.ll
llvm/trunk/test/Transforms/InstCombine/select.ll
Modified: llvm/trunk/lib/Analysis/AssumptionCache.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/AssumptionCache.cpp?rev=292239&r1=292238&r2=292239&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/AssumptionCache.cpp (original)
+++ llvm/trunk/lib/Analysis/AssumptionCache.cpp Tue Jan 17 12:15:49 2017
@@ -47,9 +47,11 @@ void AssumptionCache::updateAffectedValu
} else if (auto *I = dyn_cast<Instruction>(V)) {
Affected.push_back(I);
- if (I->getOpcode() == Instruction::BitCast ||
- I->getOpcode() == Instruction::PtrToInt) {
- auto *Op = I->getOperand(0);
+ // Peek through unary operators to find the source of the condition.
+ Value *Op;
+ if (match(I, m_BitCast(m_Value(Op))) ||
+ match(I, m_PtrToInt(m_Value(Op))) ||
+ match(I, m_Not(m_Value(Op)))) {
if (isa<Instruction>(Op) || isa<Argument>(Op))
Affected.push_back(Op);
}
Modified: llvm/trunk/lib/Analysis/ValueTracking.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/ValueTracking.cpp?rev=292239&r1=292238&r2=292239&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/ValueTracking.cpp (original)
+++ llvm/trunk/lib/Analysis/ValueTracking.cpp Tue Jan 17 12:15:49 2017
@@ -553,6 +553,13 @@ static void computeKnownBitsFromAssume(c
KnownOne.setAllBits();
return;
}
+ if (match(Arg, m_Not(m_Specific(V))) &&
+ isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
+ assert(BitWidth == 1 && "assume operand is not i1?");
+ KnownZero.setAllBits();
+ KnownOne.clearAllBits();
+ return;
+ }
// The remaining tests are all recursive, so bail out if we hit the limit.
if (Depth == MaxDepth)
Modified: llvm/trunk/test/Transforms/InstCombine/assume.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/assume.ll?rev=292239&r1=292238&r2=292239&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/assume.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/assume.ll Tue Jan 17 12:15:49 2017
@@ -176,13 +176,13 @@ define i32 @icmp2(i32 %a) #0 {
ret i32 %lnot.ext
}
-; FIXME: If the 'not' of a condition is known true, then the condition must be false.
+; If the 'not' of a condition is known true, then the condition must be false.
define i1 @assume_not(i1 %cond) {
; CHECK-LABEL: @assume_not(
; CHECK-NEXT: [[NOTCOND:%.*]] = xor i1 [[COND:%.*]], true
; CHECK-NEXT: call void @llvm.assume(i1 [[NOTCOND]])
-; CHECK-NEXT: ret i1 [[COND]]
+; CHECK-NEXT: ret i1 false
;
%notcond = xor i1 %cond, true
call void @llvm.assume(i1 %notcond)
Modified: llvm/trunk/test/Transforms/InstCombine/select.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/select.ll?rev=292239&r1=292238&r2=292239&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/select.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/select.ll Tue Jan 17 12:15:49 2017
@@ -1344,14 +1344,13 @@ define i8 @assume_cond_true(i1 %cond, i8
ret i8 %sel
}
-; FIXME: computeKnownBitsFromAssume() should understand the 'not' of an assumed condition.
+; computeKnownBitsFromAssume() understands the 'not' of an assumed condition.
define i8 @assume_cond_false(i1 %cond, i8 %x, i8 %y) {
; CHECK-LABEL: @assume_cond_false(
; CHECK-NEXT: [[NOTCOND:%.*]] = xor i1 %cond, true
; CHECK-NEXT: call void @llvm.assume(i1 [[NOTCOND]])
-; CHECK-NEXT: [[SEL:%.*]] = select i1 %cond, i8 %x, i8 %y
-; CHECK-NEXT: ret i8 [[SEL]]
+; CHECK-NEXT: ret i8 %y
;
%notcond = xor i1 %cond, true
call void @llvm.assume(i1 %notcond)
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