forked from OSchip/llvm-project
7f6daf1799
For pattern like ((x >> C1) & Mask) << C2, DAG combiner may convert it into (x >> (C1-C2)) & (Mask << C2), which makes pattern matching of ubfx more difficult. For example: Given %shr = lshr i64 %x, 4 %and = and i64 %shr, 15 %arrayidx = getelementptr inbounds [8 x [64 x i64]]* @arr, i64 0, %i64 2, i64 %and %0 = load i64* %arrayidx With current shift folding, it takes 3 instrs to compute base address: lsr x8, x0, #1 and x8, x8, #0x78 add x8, x9, x8 If using ubfx, it only needs 2 instrs: ubfx x8, x0, #4, #4 add x8, x9, x8, lsl #3 This fixes bug 19589 llvm-svn: 207702 |
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