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[SCCP] Remove code in visitBinaryOperator (and add tests). 

We visit and/or, we try to derive a lattice value for the
instruction even if one of the operands is overdefined.
If the non-overdefined value is still 'unknown' just return and wait
for ResolvedUndefsIn to "plug in" the correct value. This simplifies
the logic a bit. While I'm here add tests for missing cases.

llvm-svn: 287709
This commit is contained in:
Davide Italiano 2016-11-22 22:11:25 +00:00
parent 7f423442d1
commit e7ffae9dea
2 changed files with 29 additions and 15 deletions
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14
llvm/lib/Transforms/Scalar/SCCP.cpp
View File

@ -928,25 +928,17 @@ void SCCPSolver::visitBinaryOperator(Instruction &I) {
NonOverdefVal = &V2State;
if (NonOverdefVal) {
if (NonOverdefVal->isUnknown()) {
// Could annihilate value.
if (I.getOpcode() == Instruction::And)
markConstant(IV, &I, Constant::getNullValue(I.getType()));
else if (VectorType *PT = dyn_cast<VectorType>(I.getType()))
markConstant(IV, &I, Constant::getAllOnesValue(PT));
else
markConstant(IV, &I,
Constant::getAllOnesValue(I.getType()));
if (NonOverdefVal->isUnknown())
return;
}
if (I.getOpcode() == Instruction::And) {
// X and 0 = 0
if (NonOverdefVal->getConstant()->isNullValue())
return markConstant(IV, &I, NonOverdefVal->getConstant());
} else {
// X or -1 = -1
if (ConstantInt *CI = NonOverdefVal->getConstantInt())
if (CI->isAllOnesValue()) // X or -1 = -1
if (CI->isAllOnesValue())
return markConstant(IV, &I, NonOverdefVal->getConstant());
}
}

30
llvm/test/Transforms/SCCP/logical-nuke.ll
View File

@ -1,9 +1,31 @@
; RUN: opt < %s -sccp -S | grep "ret i32 0"
; RUN: opt < %s -sccp -S | FileCheck %s
; Test that SCCP has basic knowledge of when and/or nuke overdefined values.
define i32 @test(i32 %X) {
%Y = and i32 %X, 0 ; <i32> [#uses=1]
ret i32 %Y
; CHECK-LABEL: test
; CHECK: ret i32 0
define i32 @test(i32 %X) {
%Y = and i32 %X, 0
ret i32 %Y
}
; CHECK-LABEL: test2
; CHECK: ret i32 -1
define i32 @test2(i32 %X) {
%Y = or i32 -1, %X
ret i32 %Y
}
; CHECK-LABEL: test3
; CHECK: ret i32 0
define i32 @test3(i32 %X) {
%Y = and i32 undef, %X
ret i32 %Y
}
; CHECK-LABEL: test4
; CHECK: ret i32 -1
define i32 @test4(i32 %X) {
%Y = or i32 %X, undef
ret i32 %Y
}