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Correctly byte-swap APInts with bit-widths greater than 64.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@145111 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Richard Smith 2011-11-23 21:33:37 +00:00
parent 1db1c239fe
commit e73db4e2a7
2 changed files with 44 additions and 19 deletions
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45
lib/Support/APInt.cpp
View File

@ -870,30 +870,43 @@ unsigned APInt::countPopulationSlowCase() const {
return Count;
}
/// Perform a logical right-shift from Src to Dst, which must be equal or
/// non-overlapping, of Words words, by Shift, which must be less than 64.
static void lshrNear(uint64_t *Dst, uint64_t *Src, unsigned Words,
unsigned Shift) {
uint64_t Carry = 0;
for (int I = Words - 1; I >= 0; --I) {
uint64_t Tmp = Src[I];
Dst[I] = (Tmp >> Shift) | Carry;
Carry = Tmp << (64 - Shift);
}
}
APInt APInt::byteSwap() const {
assert(BitWidth >= 16 && BitWidth % 16 == 0 && "Cannot byteswap!");
if (BitWidth == 16)
return APInt(BitWidth, ByteSwap_16(uint16_t(VAL)));
else if (BitWidth == 32)
if (BitWidth == 32)
return APInt(BitWidth, ByteSwap_32(unsigned(VAL)));
else if (BitWidth == 48) {
if (BitWidth == 48) {
unsigned Tmp1 = unsigned(VAL >> 16);
Tmp1 = ByteSwap_32(Tmp1);
uint16_t Tmp2 = uint16_t(VAL);
Tmp2 = ByteSwap_16(Tmp2);
return APInt(BitWidth, (uint64_t(Tmp2) << 32) | Tmp1);
} else if (BitWidth == 64)
return APInt(BitWidth, ByteSwap_64(VAL));
else {
APInt Result(BitWidth, 0);
char *pByte = (char*)Result.pVal;
for (unsigned i = 0; i < BitWidth / APINT_WORD_SIZE / 2; ++i) {
char Tmp = pByte[i];
pByte[i] = pByte[BitWidth / APINT_WORD_SIZE - 1 - i];
pByte[BitWidth / APINT_WORD_SIZE - i - 1] = Tmp;
}
return Result;
}
if (BitWidth == 64)
return APInt(BitWidth, ByteSwap_64(VAL));
APInt Result(getNumWords() * APINT_BITS_PER_WORD, 0);
for (unsigned I = 0, N = getNumWords(); I != N; ++I)
Result.pVal[I] = ByteSwap_64(pVal[N - I - 1]);
if (Result.BitWidth != BitWidth) {
lshrNear(Result.pVal, Result.pVal, getNumWords(),
Result.BitWidth - BitWidth);
Result.BitWidth = BitWidth;
}
return Result;
}
APInt llvm::APIntOps::GreatestCommonDivisor(const APInt& API1,
@ -1232,11 +1245,7 @@ APInt APInt::lshr(unsigned shiftAmt) const {
// If we are shifting less than a word, compute the shift with a simple carry
if (shiftAmt < APINT_BITS_PER_WORD) {
uint64_t carry = 0;
for (int i = getNumWords()-1; i >= 0; --i) {
val[i] = (pVal[i] >> shiftAmt) | carry;
carry = pVal[i] << (APINT_BITS_PER_WORD - shiftAmt);
}
lshrNear(val, pVal, getNumWords(), shiftAmt);
return APInt(val, BitWidth).clearUnusedBits();
}

18
test/Transforms/ConstProp/bswap.ll
View File

@ -1,6 +1,6 @@
; bswap should be constant folded when it is passed a constant argument
; RUN: opt < %s -constprop -S | not grep call
; RUN: opt < %s -constprop -S | FileCheck %s
declare i16 @llvm.bswap.i16(i16)
@ -8,18 +8,34 @@ declare i32 @llvm.bswap.i32(i32)
declare i64 @llvm.bswap.i64(i64)
declare i80 @llvm.bswap.i80(i80)
; CHECK: define i16 @W
define i16 @W() {
; CHECK: ret i16 256
%Z = call i16 @llvm.bswap.i16( i16 1 ) ; <i16> [#uses=1]
ret i16 %Z
}
; CHECK: define i32 @X
define i32 @X() {
; CHECK: ret i32 16777216
%Z = call i32 @llvm.bswap.i32( i32 1 ) ; <i32> [#uses=1]
ret i32 %Z
}
; CHECK: define i64 @Y
define i64 @Y() {
; CHECK: ret i64 72057594037927936
%Z = call i64 @llvm.bswap.i64( i64 1 ) ; <i64> [#uses=1]
ret i64 %Z
}
; CHECK: define i80 @Z
define i80 @Z() {
; CHECK: ret i80 -450681596205739728166896
; 0xA0908070605040302010
%Z = call i80 @llvm.bswap.i80( i80 76151636403560493650080 )
; 0x102030405060708090A0
ret i80 %Z
}