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Make InstCombiner::FoldAndOfICmps create a ConstantRange that's the

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intersection of the LHS and RHS ConstantRanges and return "false" when
the range is empty.

This simplifies some code and catches some extra cases.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@126744 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Anders Carlsson 2011-03-01 15:05:01 +00:00
parent 32e20a45e5
commit d70be0b2c1
2 changed files with 21 additions and 8 deletions
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20
lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
View File

@ -14,6 +14,7 @@
#include "InstCombine.h"
#include "llvm/Intrinsics.h"
#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/Support/ConstantRange.h"
#include "llvm/Support/PatternMatch.h"
using namespace llvm;
using namespace PatternMatch;
@ -767,7 +768,17 @@ Value *InstCombiner::FoldAndOfICmps(ICmpInst *LHS, ICmpInst *RHS) {
LHSCC == ICmpInst::ICMP_SGE || LHSCC == ICmpInst::ICMP_SLE ||
RHSCC == ICmpInst::ICMP_SGE || RHSCC == ICmpInst::ICMP_SLE)
return 0;
// Make a constant range that's the intersection of the two icmp ranges.
// If the intersection is empty, we know that the result is false.
ConstantRange LHSRange =
ConstantRange::makeICmpRegion(LHSCC, LHSCst->getValue());
ConstantRange RHSRange =
ConstantRange::makeICmpRegion(RHSCC, RHSCst->getValue());
if (LHSRange.intersectWith(RHSRange).isEmptySet())
return ConstantInt::get(CmpInst::makeCmpResultType(LHS->getType()), 0);
// We can't fold (ugt x, C) & (sgt x, C2).
if (!PredicatesFoldable(LHSCC, RHSCC))
return 0;
@ -800,10 +811,6 @@ Value *InstCombiner::FoldAndOfICmps(ICmpInst *LHS, ICmpInst *RHS) {
case ICmpInst::ICMP_EQ:
switch (RHSCC) {
default: llvm_unreachable("Unknown integer condition code!");
case ICmpInst::ICMP_EQ: // (X == 13 & X == 15) -> false
case ICmpInst::ICMP_UGT: // (X == 13 & X > 15) -> false
case ICmpInst::ICMP_SGT: // (X == 13 & X > 15) -> false
return ConstantInt::get(CmpInst::makeCmpResultType(LHS->getType()), 0);
case ICmpInst::ICMP_NE: // (X == 13 & X != 15) -> X == 13
case ICmpInst::ICMP_ULT: // (X == 13 & X < 15) -> X == 13
case ICmpInst::ICMP_SLT: // (X == 13 & X < 15) -> X == 13
@ -851,9 +858,6 @@ Value *InstCombiner::FoldAndOfICmps(ICmpInst *LHS, ICmpInst *RHS) {
case ICmpInst::ICMP_SLT:
switch (RHSCC) {
default: llvm_unreachable("Unknown integer condition code!");
case ICmpInst::ICMP_EQ: // (X s< 13 & X == 15) -> false
case ICmpInst::ICMP_SGT: // (X s< 13 & X s> 15) -> false
return ConstantInt::get(CmpInst::makeCmpResultType(LHS->getType()), 0);
case ICmpInst::ICMP_UGT: // (X s< 13 & X u> 15) -> no change
break;
case ICmpInst::ICMP_NE: // (X s< 13 & X != 15) -> X < 13

9
test/Transforms/InstCombine/and2.ll
View File

@ -26,3 +26,12 @@ define i32 @test3(i32 %X, i32 %Y) {
; CHECK-NEXT: and i32 %X, %Y
; CHECK-NEXT: ret
}
define i1 @test4(i32 %X) {
%a = icmp ult i32 %X, 31
%b = icmp slt i32 %X, 0
%c = and i1 %a, %b
ret i1 %c
; CHECK: @test4
; CHECK-NEXT: ret i1 false
}