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Optimize memcmp(x,y,n)==0 for small n and suitably aligned x/y. 

http://reviews.llvm.org/D6952
PR20673

llvm-svn: 246313
This commit is contained in:
Chad Rosier 2015-08-28 18:30:18 +00:00
parent 3171cabb34
commit dc65532fd9
2 changed files with 74 additions and 1 deletions
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22
llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
View File

@ -32,6 +32,7 @@
#include "llvm/Support/CommandLine.h"
#include "llvm/Analysis/TargetLibraryInfo.h"
#include "llvm/Transforms/Utils/BuildLibCalls.h"
#include "llvm/Transforms/Utils/Local.h"
using namespace llvm;
using namespace PatternMatch;
@ -862,6 +863,27 @@ Value *LibCallSimplifier::optimizeMemCmp(CallInst *CI, IRBuilder<> &B) {
return B.CreateSub(LHSV, RHSV, "chardiff");
}
// memcmp(S1,S2,N/8)==0 -> (*(intN_t*)S1 != *(intN_t*)S2)==0
if (DL.isLegalInteger(Len * 8) && isOnlyUsedInZeroEqualityComparison(CI)) {
IntegerType *IntType = IntegerType::get(CI->getContext(), Len * 8);
unsigned PrefAlignment = DL.getPrefTypeAlignment(IntType);
if (getKnownAlignment(LHS, DL, CI) >= PrefAlignment &&
getKnownAlignment(RHS, DL, CI) >= PrefAlignment) {
Type *LHSPtrTy =
IntType->getPointerTo(LHS->getType()->getPointerAddressSpace());
Type *RHSPtrTy =
IntType->getPointerTo(RHS->getType()->getPointerAddressSpace());
Value *LHSV = B.CreateLoad(B.CreateBitCast(LHS, LHSPtrTy, "lhsc"), "lhsv");
Value *RHSV = B.CreateLoad(B.CreateBitCast(RHS, RHSPtrTy, "rhsc"), "rhsv");
return B.CreateZExt(B.CreateICmpNE(LHSV, RHSV), CI->getType(), "memcmp");
}
}
// Constant folding: memcmp(x, y, l) -> cnst (all arguments are constant)
StringRef LHSStr, RHSStr;
if (getConstantStringInfo(LHS, LHSStr) &&

53
llvm/test/Transforms/InstCombine/memcmp-1.ll
View File

@ -2,7 +2,7 @@
;
; RUN: opt < %s -instcombine -S | FileCheck %s
target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:128:128"
target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:128:128-n8:16:32:64"
@foo = constant [4 x i8] c"foo\00"
@hel = constant [4 x i8] c"hel\00"
@ -70,3 +70,54 @@ define i32 @test_simplify6() {
ret i32 %ret
; CHECK: ret i32 -1
}
; Check memcmp(mem1, mem2, 8)==0 -> *(int64_t*)mem1 == *(int64_t*)mem2
define i1 @test_simplify7(i64 %x, i64 %y) {
; CHECK-LABEL: @test_simplify7(
%x.addr = alloca i64, align 8
%y.addr = alloca i64, align 8
store i64 %x, i64* %x.addr, align 8
store i64 %y, i64* %y.addr, align 8
%xptr = bitcast i64* %x.addr to i8*
%yptr = bitcast i64* %y.addr to i8*
%call = call i32 @memcmp(i8* %xptr, i8* %yptr, i32 8)
%cmp = icmp eq i32 %call, 0
ret i1 %cmp
; CHECK: %cmp = icmp eq i64 %x, %y
; CHECK: ret i1 %cmp
}
; Check memcmp(mem1, mem2, 4)==0 -> *(int32_t*)mem1 == *(int32_t*)mem2
define i1 @test_simplify8(i32 %x, i32 %y) {
; CHECK-LABEL: @test_simplify8(
%x.addr = alloca i32, align 4
%y.addr = alloca i32, align 4
store i32 %x, i32* %x.addr, align 4
store i32 %y, i32* %y.addr, align 4
%xptr = bitcast i32* %x.addr to i8*
%yptr = bitcast i32* %y.addr to i8*
%call = call i32 @memcmp(i8* %xptr, i8* %yptr, i32 4)
%cmp = icmp eq i32 %call, 0
ret i1 %cmp
; CHECK: %cmp = icmp eq i32 %x, %y
; CHECK: ret i1 %cmp
}
; Check memcmp(mem1, mem2, 2)==0 -> *(int16_t*)mem1 == *(int16_t*)mem2
define i1 @test_simplify9(i16 %x, i16 %y) {
; CHECK-LABEL: @test_simplify9(
%x.addr = alloca i16, align 2
%y.addr = alloca i16, align 2
store i16 %x, i16* %x.addr, align 2
store i16 %y, i16* %y.addr, align 2
%xptr = bitcast i16* %x.addr to i8*
%yptr = bitcast i16* %y.addr to i8*
%call = call i32 @memcmp(i8* %xptr, i8* %yptr, i32 2)
%cmp = icmp eq i32 %call, 0
ret i1 %cmp
; CHECK: %cmp = icmp eq i16 %x, %y
; CHECK: ret i1 %cmp
}