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Fix instruction check failure of UBFX and SBFIZ in testb3 due to the …
…speculative fix in bug 227554 https://bugs.webkit.org/show_bug.cgi?id=227563 Patch by Yijia Huang <email@example.com> on 2021-07-06 Reviewed by Filip Pizlo. This patch includes two modifications to resolve rdar://79978150: 1. Fix the bug caused by the patch introducing BFI. 2. Discard the corresponding speculative fix in https://bugs.webkit.org/show_bug.cgi?id=227554. The previous patch, added bit field insert (BFI) to AIR opcode, causes the Gmail page hanging issue on Safari. The root cause is the incorrect definition of register role in BFI's AIR opcode. Since BFI inserts a bit field at the low end of the destination register while keeping the high bit unchanged, the destination register should have both roles of use and define simultaneously, which is not (missing use) in the previous patch. This will result in the loss of preserving the value of the destination register, which does happen when browsing the Gmail page on Safari. // B3 IR snippets from Gmail Int32 b@23 = Add(b@104, b@111, D@100) ... Int32 b@55 = Const32(65535, D@50) Int32 b@137 = BitAnd(b@118, $65535(b@55), D@160) Int32 b@168 = Const32(16, D@40) Int32 b@141 = Shl(b@137, $16(b@168), D@163) Int32 b@143 = BitAnd(b@23, $65535(b@55), D@166) Int32 b@144 = BitOr(b@141, b@143, D@169) The pattern of BFI is d = ((n & mask1) << lsb) | (d & mask2). So, it is obvious that BFI can be utilized in b@144 where the d is b@23. // Incorrect AIR opcode of BFI arm64: InsertBitField32 U:G:32, U:G:32, U:G:32, ZD:G:32 Tmp, Imm, Imm, Tmp // Air w/o use role Add32 %x3, %x7, %x7, b@23 ... InsertBitField32 %x3, $16, $16, %x4, b@144 // Generated code w/o use role add w7, w3, w7 ... bfi w4, w3, #16, #16 In Air, the added value is stored in the w7. But the value is not preserved after lowering with BFI. To fix this, the use role should be enabled for the destination register. // Correnct AIR opcode of BFI arm64: InsertBitField32 U:G:32, U:G:32, U:G:32, UZD:G:32 Tmp, Imm, Imm, Tmp // Air w/ use role Add32 %x3, %x7, %x7, b@23 ... Move32 %x7, %x4, b@144 InsertBitField32 %x3, $16, $16, %x4, b@144 // Generated code w/ use role add w7, w3, w7 ... ubfx x4, x7, #0, #32 bfi w4, w3, #16, #16 In addition, BFXIL, which has pattern d = ((n >> lsb) & mask1) | (d & mask2), also needs the similar update. * b3/B3LowerToAir.cpp: * b3/air/AirOpcode.opcodes: * b3/testb3_2.cpp: (testInsertBitField32): (testInsertBitField64): (testExtractInsertBitfieldAtLowEnd32): (testExtractInsertBitfieldAtLowEnd64): * runtime/OptionsList.h: Canonical link: https://commits.webkit.org/239419@main git-svn-id: https://svn.webkit.org/repository/webkit/trunk@279593 268f45cc-cd09-0410-ab3c-d52691b4dbfc
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