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Fix detection of valid BFC immediates.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@75576 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
David Goodwin 2009-07-14 00:57:56 +00:00
parent 1a8d2d2d4f
commit c2ffd286af
2 changed files with 16 additions and 10 deletions
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20
lib/Target/ARM/ARMInstrInfo.td
View File

@ -168,16 +168,16 @@ def bf_inv_mask_imm : Operand<i32>,
uint32_t v = (uint32_t)N->getZExtValue();
if (v == 0xffffffff)
return 0;
// naive checker. should do better, but simple is best for now since it's
// more likely to be correct.
while (v & 1) v >>= 1; // shift off the leading 1's
if (v)
{
while (!(v & 1)) v >>=1; // shift off the mask
while (v & 1) v >>= 1; // shift off the trailing 1's
}
// if this is a mask for clearing a bitfield, what's left should be zero.
return (v == 0);
// there can be 1's on either or both "outsides", all the "inside"
// bits must be 0's
unsigned int lsb = 0, msb = 31;
while (v & (1 << msb)) --msb;
while (v & (1 << lsb)) ++lsb;
for (unsigned int i = lsb; i <= msb; ++i) {
if (v & (1 << i))
return 0;
}
return 1;
}] > {
let PrintMethod = "printBitfieldInvMaskImmOperand";
}

6
test/CodeGen/Thumb2/thumb2-bfc.ll
View File

@ -17,3 +17,9 @@ define i32 @f3(i32 %a) {
%tmp = and i32 %a, 4095
ret i32 %tmp
}
; 2147483646 = 0x7ffffffe not implementable w/ BFC
define i32 @f4(i32 %a) {
%tmp = and i32 %a, 2147483646
ret i32 %tmp
}