diff options
| -rw-r--r-- | llvm/lib/Target/ARM/ARMInstrInfo.td | 20 | ||||
| -rw-r--r-- | llvm/test/CodeGen/Thumb2/thumb2-bfc.ll | 6 |
2 files changed, 16 insertions, 10 deletions
diff --git a/llvm/lib/Target/ARM/ARMInstrInfo.td b/llvm/lib/Target/ARM/ARMInstrInfo.td index b3a52d65f17..17e7365962b 100644 --- a/llvm/lib/Target/ARM/ARMInstrInfo.td +++ b/llvm/lib/Target/ARM/ARMInstrInfo.td @@ -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"; } diff --git a/llvm/test/CodeGen/Thumb2/thumb2-bfc.ll b/llvm/test/CodeGen/Thumb2/thumb2-bfc.ll index 1e5016c9129..a612b9bb888 100644 --- a/llvm/test/CodeGen/Thumb2/thumb2-bfc.ll +++ b/llvm/test/CodeGen/Thumb2/thumb2-bfc.ll @@ -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 +} |
